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MM 007 : Coated
GALVANIZE
Two Types • Hot Dipped
ElectrJLytic
HOT DIPPED GALVANIZE
Two Types
• Zendzimir
Cooke – Nortemari
GALVANIZE PRODUCT
Advantages:
• Corrosion Protection
• Fonnab le
• Paintable
Disadvantages:
• Weldability
GALVANNEAL PRODUCT
Advantages:
• Corrosion Protection
*
• Paintable
• Weldable
Disadvantages:
• Less Formable
• Lead Times
MINIMUM SPANGLE
Produced Two Ways
• Steam
Zinc Dust (Heurtey)
CHEMICAL TREATMENTS
Chrornate (passivation) Phosphate
COATING COMPARISONS
PRODUCT
Galvanize
Galvanneal
Electrogalvanize
Galvalume
Aluminum (Type 1)
Aluminum (Type 2)
COATING 99.5% Zinc 99.5% Zinc 100% Zinc
55% Aluminum 45% Zinc
95% Aluminum 5% Silicon
100% Aluminum
EXHIBIT #1 - Coatings for Steel Sheet Products
Types of Coatings
Description
I. Hot Dip Zinc Coated
Regular and Minimized Spangle
I This product Is made on continuous hot dip galvanizing lines and is supplied In colls and cut lengths.
The product includes regular and minimized spangle In a wide range of coating designations (ASTM A525/A525M) and is available In extra smooth
finish.
2. Hot Dip Zinc Coated
Fully Alloyed Zinc-Iron Coated
Hot-dip zinc coated product that is heat treated or wiped to produce a fully alloyed zinc-iron coating.
3. Hot Dip Zinc Coated Differentially Zinc Coated
Hot-dip zinc coated product that is produced with different specified coat-Ing weights on opposite sheet surfaces — being significantly lighter on one
surface. Both surfaces zinc.
4. Hot Dip Zinc Coated
Differentially Zinc-Iron Coated
Same as Coating #3 excettt the coating on the lighter surface is ;.eat treated or wiped to produce a fully alloyed zinc-iron coating.
5. Hot Dip Zinc Coated (One Side)
This product is produced with a continuous hot dip zinc coating on one side of the sheet and a zinc free, cold rolled steel surface on the other for
superior paintabllity.
6. Electrolytic Zinc Flash Coated
Electrolytic zinc coated steel is produced by continuously flash electroplating with zinc — 3 grams to 6 grams per square meter total on both sides. It Is
used when minimal corrosion resistance is required.
Steel Service Center Institute -
12
Types of Coatings
Description
7. Electroplated Zinc Coated
Produced by continuously electroplating zinc. Two aide coatings can be produced on an equal basis for differentially total coating. One aide product has
a standard cold rolled surface. Generally 2 side coatings have a 140 g/ma.
8. Electropla:. J Iron Zinc Alloy Coated
Thl» product Is produced by the simultaneous electroplating of zinc and Iron to form an alloy coating. One and two side coatings can be produced on an
equal basis or differentially coated.
9. Electroplated Zinc NickeJ Alloy Coated
10. Aluminum Coated
11. Aluminum
Zinc Coated (GALVALUME)
12. Zinc-Aluminum/
Mischmetal Coated (GALFAN)
• This product is produced by the simultaneous electroplating of zinc and nickel to form an aBoy coating. One and two side coatings can be produced on
an equal basis or differentially coated.
• Aluminum coated 3teel Is produced by hot itiip coating cold rolled sheet steel on continuous lines. It provides a material with the superior strength of
steel and the surface properties of aluminum.
• Aluminum-zinc alley coated steel is produced by hot dip coating cold rolled sheet steel on continuous lines. It has the superior strength of steel and
excellent corrosion resistance, plus heatt resistance.
• Coaled steel is produced by hot-dip coating on continuous lines. It provides excellent formablllty and excellent corrosion resistance.
13. LongTeme
• Colcd rolled sheet steel Is coated on both sides with a lead-tin alloy by a continuous hot dip proce&s.
13
Steel Service Center Institute •
Types of Coatings
Description
14. Nickel Teme
Cold rolled sheet steel electrolytically nickel flash plated and then coated on both sides with a lead-tin alloy by a continuous hot dip process. Corrosion
resistance is superior to standard long terne.
15. Tin Coated
16. Ztncrometal*
Cold rolled sheet steel coated with tin by a continuous electrolytic process.
A cold rolled sheet product with a base coat containing primarily chromium and zinc, top coated by a weldable zinc rich primer for corrosion resistance,
generally to only one side, with the other side being a standard cold rolled surface for superior paintabllity.
17. Coll Coated (Pre-Palnted)
A carbon steel sheet Is first coated wtth a metallic coating for protection and then coil-line painted.
NOTES:
Steel Senrice Center Institute •
14
TV&^'$&^- Main Applications
• Zinc-Coated Sheets • Hot-dip zinc-coated Building exterior materiads, ducts, corrugated pipe, household electrical appliances, dvil engineering
products, automotive pairts. light-gauge shapes, interior matte-rials.
• Hot-dip iron-zinc alloyed Shutters, doors, household efiec-trtCSll 3T7T?iJC3nCC3 8Ut CjniOtlVC OftlffS*
interior materials.
• Hot-dip zinc -aluminum alloy-coated Building exterior materials, dvil engineering products, auitomo&fcre parts, household electrical apgtfi-
ances.
• Electrolytic zinc-coated Doors, sashes, automotive pants, household electrical appliances.
hi Electrolytic zinc alloy-coated Automotive parts, household elkc-tncal appliances.
• Hot-dip alumlnlzed sheets Combustion equipment, muffleers. exhaust pipes, exterior materials.
• Terne-coated sheets Gasoline tanks, chassis fbrTVstets. radiators.
• Tlnplate Food cans, general cans. 18-1 cans, crown caps, aerosol cans
• Organic-Coated Sheets • Prepalnted hot-dip zinc-coated Roofs, sidings. Interior materUals, temporary works, outer panelssfor appliances.
• Prepalnted hot-dip zinc-aluminum alloy-coated Roofs, sidings.
NOTES:
22
CONTINUED...
Types
Prepalnted electrolytic zinc-coated
Decorative sheets (Embossed, pattern-printed, specially finished, high-grade decorattve-nnlshed)
Precoated
Weldable precoated PVC-coated Plastic - Laminated
Main Application*
Outer panels for appliances, interior materials.
Sidings. Interior materials, storm doors, household electrical appliances.
Interior and exterior materials, household electrical apspliances.
Outer panels for appliances, building materials, automotive parts.
Hoofs, sidings, anterior materials, outer panels for appliances.
Interior and exterior materials, kitchen utensils, household electrical appliances.
CORROSION.. Ji COMPLEX PHENOMENON:
Corrosion takes many forms. It can be uniform, spreading over the entire exposed surface of a metal sheet: or it can be localized, occurring where special
conditions create a corrosive agent. It can be microscopic or, more often In the case of steel sheet, macroscopic or clearly visible.
In addition to uniform corrosion, there are several osther types of visible corrosion. Examples include crevice corrosion which occurs wlthta flssvnres
and narrow openings where water may be trapped — at gaskets, lap Joints, bolts, rivets, weldments or scratches, for example. Poultice corrosion is
common on vehicles* occurring when mud cakes up inside wheeJwells and crevices. The mud retains road saJt and water and acts to keep the metal
surface damp, promoting corrosive chemical action. Erosstve corrosion occurs when an abrasive stream of water strikes a metallic surface. Still another
form of corrosion, known as fretting, occurs when mating surfaces are subjected to seepage of an electroryte solution In combination with vibration.
These four form* of corrosion are illustrated on the following page. NOTES:
23
Steel Sertice C«nter Institute •
severe for almost any application of steel sheet in the add rain regions and where sulfur dioxide and chloride levels are high.
Coated steel sheet properly selected and applied, can combat corrosion successfully in many applications. A metallic or organic coating can protect steel
sheet from corrosive attack by acting as a barrier to exclude air. water and other corrosion promotes* from contact with the sheet AD coatings — zinc,
zinc-aluminum. zinc-Iron, teme and paints — provide excellent barrier protection.
In addition to barrier protection, zinc and zinc alloys have the ability to react to scratches and other damage through an electrochemical (galvanic) action
between steel arad zinc. This galvanic action makes It possible for the zinc to protect breaks In the coatlmg and prevent further damage.
What all of these fundamentals are meant to Illustrate Is the complexity of our suibject, and the need for this manual. We will provide a great deal of
informatlc.i. broken Into areas by the type of basic coatings: Zinc. Aluminum. Lead and Tin, Paint. We win examine within each coating type the
methods of affixing the coatings, base metal qualities, coating weights available, features and benefits of the products, and other useful data.
The idea of this manual is not to make you a metallurgist, but to supply you wttti a source of facts and information. The first places to look for answers
are the Tabfle of Contents and the Glossary of Terms.
NOTES:
25
S ieel Service Center Institute -
OF PRODUCING COATED SHEET PRODUCTS
We have the base metal, now how do the producers of coated products applj the various coatings? Hot dipping, electrolytic and coll coating for painted
products are the three basic methods.
HOT DIP PROCESS:
Typically, the hot dip process begins with an as-cold-reduced or pre-armealed steel sheet especially selected for coating. As the sheet Is uncoiled. It Is
cleaned, because a clean surface Is essential to develop a good bond between the steel and the coating. On many lines, an electrolytic cleaning unit
subjects the sheet to a combination of fast-flowing alkaline solution and electrical current for efficient removal of oils, lubricants and other surface
contaminants. Brushes remove any vestige of remaining soil as the sheet passes through scrubber units. After hot water rinsing, the sheet Is completely
dried by rubber-squeegee rolls and hot air.
The cleaned sheet then goes through a continuous-annealing furnace where at Is given either a high-temperature or pre-heac anneal to prepare it for
coating. When a significant change In mechanical properties is desired, the high-temperature cycle la usedL In this cycle, the steel is heat-treated in a
precision-controlled, oxygen-free atmosphere to provide the different strength and formabllity levels required by customer applications. The furnace is
divided into zones to allow exact control of temperatures for heating, holding and cooling the sheet as it acquires desired mechanical properties. When
either minimal or no changes in mechanical properties are desired, the steel goes through the preheating cycle. When the sheet leaves the continuous-
annealing furnace, the surface is fuDy prepared to accept a smooth, even coating.
Immediately after furnace preparation, the sheet enters the coating bath. The continuously moving sheet Is immersed in a bath of molten met-J. The
coating comocsltlora and processing temperatures are rigorously controlled to achieve the optimum bond between coating and steel.
A unique feature of the hot dtp process ts that the coating forms an adherent, fntermetoi-Uc bond with the steel substrate, so that the coating and the
steel behave as one during fabrication and service.
As the steel exits the coating bath, a thin, molten layer of the coating metal adheres, to both sides of the sheet. The sheet passes between a set of air
knives where air Is directed under pressure against the strip to regulate the thickness of the molten coating and achieve closely controlled, uniform
coating thickness.
The molten coating solidifies as the sheet moves vertically through the cooling toweT. The solidification process is controlled to Impart selective surface
finishes, such as minimized spangle, to the coating.
Steel Service Center Institute <
39
A CAUTIONARY NOTE:
It Is important to note that the amount of coating of zinc or zinc-iron coating is the prime reason customers buy galvanized products. The method of
applying the zinc to the base or substrate metal Is of secondary importance.
Using modem day systems, both hot dip and electrolytic coating methods are acceptable to most customers. If they Insist on one or the other, you
might question why. and of course know what you carry in stock.
And finally, a key for you in answering "Which of these products should I buy?", can be a variation of "What do you manufacture? What process do
you use?"
End use! As always the key to providing the customer with the product they need.
NOTES:
Steel Service Center Institute •
43
JVOTES:
Steel Sendee Center Institute •
different methods of coating base metals. These methods are reviewed in the "Methods of Coating* section. But here Is a quick explanation of each:
The hot dip process consists of passing the steel through a both of molten zinc. The electroplating process consists of the application of zinc by
electrolytic disposition.'
What we will do In the first section Is to treat hot dtp galvanized, then follow with the data on electrolytic galvanized sheets...and then gahrannealed
Base Metals (For all galvanized products): • The most common base metal for
galvanized sheets Is cold-rolled steel. Occasionally, hot-rolled will be specified. (The ASTM specification for such products will be ASTM A-568.)
NOTES:
45
Steel Service Center Institute •
HOT-DIP ZINC COATED GALVANIZED STEEL SHEET
WHAT IS IT?
A carbon steel sheet, coated with zinc on both sides of the sheet, by the continuous hot dip process. The process results in a zinc layer tightly adhering
to the base steel through an iron-zinc bonding layer. (Note: If an iron-zinc alloy is wanted, then you need galvannealed! We will discuss galvannealed
later.)
It should be noted that the standard specification for zinc-coated (galvanized) steel sheets by the hot-dip process is ASTM A653.
HOW IS IT PRODUCED?
By the continuous hot-dip process. For full details and schematic, refer to the section of "Methods of Coating".
Base Metals - Cold rolled or hot rolled steel sheets (occasionally high strength - low alioy.x, Steels - As you will see, there are six principal steels. All
are covered by ASTM A653.
Hot-dip galvanized sheet is produced in six principal steels: Commercial Steel (CS Types A, B and C) Forming Steel (FS Types A and B) Deep
Drawing Steel (DOS) Extra Deep Drawing Steel (HDDS) Structural Steel (SS) High Strength Low Alloy Steel (HSLAS Types A and B)
GALVANIZED COMMERCIAL STEEL - CS - (ASTM A653):
Ordinarily produced from rimmed, capped, semi-killed, or continuously cast steel. This steel! is generally suitable for simple bending, mild drawing and
roll forming. The customer normally furnishes information on the individual requirements of the identified part.
Sheets should stand bending at room temperature flat on themselves in any direction without fracture of the base metal. If greater ductility than the
minimum indicated by the bend test is required, or if uniformity of properties is necessary, DDS or HDDS will fill the requirements. (See DOS or
HDDS).
The zinc coating should stand bending without flaking when tested in accordance with provi sions of ASTM A653.
46
Commercial Steel can be processed after coating to improve the smoothness of surface or to control the temper.
This steel can be supplied with reasonably consistent non-fluting characteristics at the time of shipment. However, with lime, aging can occur with loss
oj ductility and return oj flailing characteristics. Fluting can be minimized by roller leveling immediately prior to fabrication.
When stretcher strains are objectionable on parts made from galvanized Commercial Steel, then temper rolled or extra smooth should be specified. Aging
will bring about reduced ductility and a return of the tendency to stretcher strain. Effective roller leveling immediately before fabrication, depending on
storage time, may eliminate or minimize strain.
Coils and cut lengths are identified as Commercial Steel or CS by showing this designation or symbol on each shipping tag. When a coating designation is
specified, it is als« shown on each shipping unit.
The quality can be specified to ASTM A653, "Steel Sheet Zinc-Coated (Galvanized) by the Hot-Dip Process. Commercial Steel."
CHEMICAL COM POSITION
CHEMICAL REQUIREMENTS
ELEMENT % TYPE A % TYPE B % TYPE C
CARBON, MAX 0.10 0.02-0.. 15 0.08
MANGANESE, MAX. 0.60 0.60 0.60
PHOSPHORUS, MAX. 0..030 0.030 0.100
SULFUR, MAX. 0.035 0.035 0.035
COPPER, WHEN SPECIFIED, MIN 0..20 0.20 0.20
47
GALVANIZED FORMING STEEL - FS (ASTM-A653):
Produced from specially processed steel and is processed to have good uniform form ing and drawing properties for use in fabricating parts having
severe deformations.
The primary difference between FS and CS sheet is that FS sheet is more ductile. FS sheet is typically used for applications where breakage (splitting)
would be encountered with CS sheet. FS sheet is produced from specially selected steels, processed for improved and more uniform formability
properties.
Forming and drawing operations must be carefully controlled by the user to provide the required performance. FS sheet is subject to the same aging
phenomenon as CS sheet; therefore, to avoid strain lines, FS sheet should be roller leveled just before the forming operation..
The steel is not commonly specified as to chemical composition, and is generally tfurnished for use in fabricating an identified part too difficult for the
fabricating properties of galvanized commercial steel.
The customer normally furnishes information on the individual requirements of an idlentified part.
There are no established standards with respect to the flaking of coating during fabrication; hence, care should be taken to ensure that the coating
designation is compatible with the end application involved.
Forming Steel is not ordinarily processed to control the phenomenon kn*own as stretcher strains.
When stretcher strains are objectionable on parts made from galvanized Forming Ste:el, temper rolled or extra smooth should be specified. Aging will
bring about reduced ductility and a return of the tendency to stretcher strain. Effective roller leveling immediately before fabrication, depending on the
storage time, may eliminate or minimize stretcher straining.
Delays between draws may detrimentally affect the properties of the steel.
Coils and cut lengths are identified as Forming Steel or FS by showing this designation or symbol on each shipping unit. When a coating designation is
specified, it is also shown on each shipping unit.
Sheet steel of this grade can be specified to ASTM A653, "Steel Sheet, Zinc-Coated (Galvanized by the Hot-Dip Process Forming Steel)."
48
ASTM A653 FORMING STEELS: (Continued)
This steel is intended for fabricating identified parts which involve forming or drawing beyond the requirements of commercial quality. These sheets
nnay also be susceptible to aging with lime and are sold on the basis of chemistry without certified mechanical properties. Forming steel is not intended
for those applications that require good drawing properties.
Material supplied under this specification shall meet the applicable requirements of the latest revision of Specification A653 unless otherwise specified.
CHEMICAL COMPOSITIONS
CHEMICAL REQUIREMENTS
ELEMENT TYPE A TYPEB
CARBON 0.10 MAX. 0.02/0.10
MANGANESE 0.50 MAX. 0.50 MAX.
PHOSPHORUS 0.020 MAX. 0.020 MAX.
SULFUR 0.035 MAX. 0.030 MAX.
GALVANIZED DEEP DRAWING STEEL (DPS) AND EXTRA DEEP DRAWING STEEL (EDDS)
Generally a low carbon aluminum killed steel, although the producer sometimes uses other deoxidizers to obtain the proper characteristics.
These steels are not commonly specified to chemical composition and are generally furnished for use in fabricating an identified part where draw or
forrraation is particularly severe or where the material is to be essentially free from significant changes in mechanical properties over a period of time.
The customer normally furnishes information on the individual requirements of the identified
part.
DOS & EDDS should be specified where the formed material! is to be essentially free of such surface disturbances as stretcher strains or fluting without
the need of prior roller leveling.
There are no established standards with respect to the flaking of coating during fabrication; hence, care should be taken to ensure that the coating
designation is compatible with the end application involved.
49
Material supplied under this specification shall meet the applicable requirements of the latest revision of Specification A653 unless otherwise specified
herein.
CHEMICAL COMPOSITIONS
CHEMICAL REQUIREMENTS
ELEMENT DOS EDDS
CARBON 0.06 MAX. 0.02 MAX
MANGANESE 0.50 MAX. 0.40 MAX
PHOSPHORUS 0.020 MAX. 0.020 MAX.
SULFUR 0.025 MAX. 0.020 MAX.
ALUMINUM 0.01 MIN. 0.01 MIN.
GALVANIZED STRUCTURAL STEEL SS (ASTM A-653):
Produced when mechanical properties are specified or required other than that indicated by the base metal bend test of commercial quality. Such
properties or values include those indicated by tension, hardness or other commonly accepted mechanical tests. For most applications, only one kind of
test requirement is normally applied. Hardness tests are made on specimens stripped of coating. Tension tests are usually made in accordance with
ASTM A653.
SS sheet is recommended for applications in which specific mechanical properties are required for strength in a finished part, usually in load-bearing
structures. Orders for SS usually require that minimum yield and tensile strengths or a minimum hardness value (Rockwell B) be met by the steel
producer. When specified minimum yield strength is 35 ksi or greater, Structural Steel sheet is classified as high strength sheet. When specifying an SS
grade, the user should carefully consider the compatibility of the specified properties with forming requirements. In general, steels produced to meet
increasing yield strength levels have a corresponding decrease in ductility or formability.
Normally, the formability of Structural Steel sheet decreases with increasing yield strength and/or hardness. Therefore, for the proper and economical
utilization of Structural Steel sheet, product design should be considered by the consumer.
Structural Steel is ordinarily furnished with the sulfur content up to 0.040 percent by heat
analysis.
Coils and cut lengths are identified as Structural Steel or SS by showing this designation or symbol on each shipping unit. When a coating designation is
specified, it is also shown on each shipping unit. Sheet steel is commonly specified to ASTM A653, "Steel Sheet, Zinc-Coated (Galvanized) by the Hot-
Dip Process, Structural Steel."
50
CHEMICAL REQUIREMENTS
DESIGNATION COMPOSITION % (MAX)
SS GRADE CARB. MANG. PHOS. SULF.
33 0.20 ..... 0.04 0.04 :
37 0.20 ..-. 0.10 0.04
40 0.25 .... 0.10 0.04
50 CL 1 & 2 0.40 ..„. 0.20 0.04 ;
50CL3 0.50 ..... 0.04 0.04
80 0.20 ..... 0.04 0.04
HSLASTYPEA
50 0.20 1.20 •••• 0.035
60 0.20 1,35 • ••• 0.035
70 0.20 1,65 ..*. 0.035
80 0.20 1,65 .... 0.035
HSLAS TYPE B
50 0.15 1.20 *.*• 0.035
60 0.15 1.20 .... 0.035
70 0.15 1.65 .... 0.035
80 0.15 1.65 *••• 0.035
Where an ellipsis (....) appears there is no requirement, but the amalysis shall be reported.
Steel conforming to this designation commonly contains the stremgthening elements columbium, nit.Togen, phosphorus or vanadium, added singly or in
combination
Some steels may be treated by means of small alloy additions to effect sulfide inclusion control.
51
MECHANICAL REQUIREMENTS
BASE METAL (LONGITUDINAL)
DESIGNATION TYPE GRADE Y.S. MIN./KSI T.S. MIN./KSI %EL MIN./2"
SS .... 33 33 45 20
37 37 52 18
40 40 55 16
50CL1 50 65 12
50CL2 50 .... 12
50CL3 50 70 12
80 80 82 ....
HSLAS TYPE A 50 50 60 20
60 60 70 16
70 70 80 12
80 80 90 10
HSLAS TYPEB 50 50 60 22
60 60 70 18
70 70 80 14
80 80 90 12
NOTE 1 - If the hardness result is 85 HRB or higher, no tension'test is required. NOTE 2 - Where an ellipsis (....) appears in this table there is no
requirement.
52
The next chart shows "typical"mechanical properties
TYPICAL MECHANICAL PROPERTIES FOR HOT-DIP PRODUCT
DESIGNATION YIELD TENSILE %EL Rb
CS - TYPE A 20/50 38/60 20MIN 4€/70
CS - TYPE B 30/60 43/65 20MIN 45/70
CS - TYPE C 20/50 40/60 20MIN 40/73
FS - TYPE A 20/45 35/50 30MIN 30/60
FS - TYPE B 25/45 38/55 25MIN 35/65
DDS 20/35 35/50 32MIN 32/55
EDDS 15/25 32/45 40MIN 30/44
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COATINGS:
As staled, one of the most important aspects of galvanized products is the coating thickness. Measured as coating weight in ounces per square foot or
grams per square meter, it is an important factor in the effective application of galvanized sheet. The coating weight should be chosen carefully, with full
attention to the fabrication method and type of environment im \\hicli the sheet will be expected to serve. In general, the effectiveness of the zinc coating
to protect the steel substrate from corrosion in any given environment is directly proportional to the coating thickness. For example, for any specific set
of environmental conditions, a G90 coating will last about 50 percent longer than a G60 coating - maintenance, painting and all other factors being equal.
Factors in addition to corrosion resistance must be considered when selecting coating thickness. For example, tthe adherence of the coating generally is
inversely proportional to the thickness; therefore, a thin coating is more desirable for applications involving high amounts of forming. Also, spot welding
becomes more difficult as the coating thickness
increases.
The weight of coating may be specified as a coating designation or as a minimum coating test limit such as the striple spot or single spot test. The
methods of sampling and testing follow the provisions of American Society for testing and Material (ASTM) Specification A653. The weight of the
coating is the total amount on both sides of a sheet, expressed in ounces per square foot of sheet, or in the metric system grams per square meter.
COATING DESIGNATION AND MINIMUM COATING TEST LIMITS (ASTM A653)
INCH - POUND UNITS OZ/FT
TYPE COATING DESIGNATION TOTAL BOTH SIDES ONE SIDE TOTAL BOTH SIDES
ZINC G360 3.260 1.28 3.20
G300 3 00 1.04 2.60
G235 2.35 0.80 2.00
G2IO 2.10 0.72 1.80
GI85 1 .85 0.64 1.60
G165 1 .65 0.58 1.40
G140 1 .40 0.48 1.20
G115 1 .15 0.40 1.00
G90 01.90 0.32 0.80
G60 0.60 0.20 0.50
G40 0.40 0.12 0.30
G30 O.30 0.10 0.25
G01 NO MIN NO MIN NO MIN
ZINC-IRON A 60 0.60 0.20 0.50
A 40 10.40 0.12 0.30
A 25 '0.25 0.08 0.20
A01 NO MIN NO MIN NO MIN
NOTE I The weight of coaling in ounces per square foot refers to the ttotal coaling on both surfaces. The coauing designation numiber is the term b\
which this product is specified.
54
(NOTES CONTINUED)
NOTE 2: As it is an established fact that the atmospheric corrosion resistance of mill galvanized sheet product is a direct function of coating weight
(thickness), the selection of lighter coating designations will result in almost nearly reduced corrosion performance of the zinc coating. For example, the
heavier galvanized coatings perform adequately in bold atmospheric exposure, whereas the lighter weight coatiings are often further coated with paint or
similar barrier coating for increased corrosion resistance. Because of this relationship, products carrying the statement, "meets ASTM A653
requirements" should also specify coating weight designation.
COATING DESIGNATORS:
G = Free Zinc
A = Zinc-Iron Alloy (Galvannealed)
X = No Coating, i.e. - one side (Metric)
E = Exposed Part (metric)
U = Unexposed Pan (Metric)*
Ni = Nickel
A WORD OF EXPLANATION ON COATING WEIGHTS:
A G90 coating means that the material is a hot-dip galvanized product, with a minimum coating weight (triple spot average).
The triple spot average covers an edge-center-edge sampling to determine adequate coverage across the sheet width. To convert coating weight from oz.
/sq. ft. to g./sq.m., the following factor cam be used: g./sq.m. = oz./sq.ft. x 305.15
Note that although a precise conversion between ASTM A653 "G" categories (G30, G60, etc.) and the metric categories (20/20, 40/40, etc.) cannot be
made, a G60 coating category (ASTM A653) is approximately equal to a 90/90 coating category (metric).
NOTE: A "U" after an "ounce per square foot", means the product is (G90) UL approved.
55
TYPES OF COATINGS
One Side Coated - Has a specified coating designation on one surface for corrosion protection and the other surface being tree of coating that will be
suitable for painting. The coating side normally has a spangled appearance. It is commonly produced to an equivalent coating weight of G60 or G90.
Extra Smooth or Temper Rolled - Is furnished when a higher degree of surface smoothness is required than is normal for as-coated galvanized or to
minimize flatting or stretcher straining. There may be variations in the coating practices and types of coat employed, but the extra smooth product is
always temper rolled. Some loss in ductility is associated with temper rolling.
Extra smooth galvanized in coils or cut lengths may contain slight coating imperfections which can be removed with a reasonable amount of light metal
finishing.
A WORD OF EXPLANATION ON COATINGS:
Zinc has a lower melting point (787 degrees F) than steel, and a lower boiling point (about 1660 degree F). During welding, zinc vapor burns in the air to
produce dense, white zinc oxide fumes which require adequate ventilation. Specific precautions are given in ANSI Publication Z49.1 Safety in Welding
and Cutting. The thicker the zinc coating, the more fumes that are generated. In general, resistance welding is preferred for joining galvanized sheet
products because it results in less fuming than other types of welding.
NOTES:
56
BEND TESTING:
ASTM A653
Coating Bend Test Requirements * For ES, FS, DOS and EDDS
Ratio of Bend Diameter to Thickness of Specimen (any direction)
Galvanized Sheet Thickness
Coating Designation 0.1 756 in to 0.0748 in. 0.0747 in. to 0.0382 in. 0.0381 in. to 0.0131
G235 3 3 2
G210 2 2 2
G185 2 2 2
G165 2 2 2
G140 2 1 1
G115 1 0 0
G90 1 0 0
G60 0 0 0
G01 0 0 0
* This table does not apply to Structural Steel and Alloy Coatings.
NOTE: For Structural Steel (SS) and High Strength Low Alloy Steel (HSLAS) Bend Test Requirements refer to ASTM A653.
57
THICKNESS:
ASTM A653
Thickness Tolerances of Hot-Dip Galvanized Sheet
NOTE 1: Thickness is measured at any point across the width not less than 3/8 in. from a siide edge.
NOTE 2: The specified thickness range captions noted below also apply when sheet is specified to a nominal thickness and the below tolerances are
divided equally, over and under.
Thickness Tolerances for Widths and Thicknesses, Tolerances all over - none under
Specified Thickmess, in..
Specified Width, In. Over 0.101 to 0.1 87, incl. Over 0.075 to 0.101, inc. OverO.(061 to 0.015, inc. Over 0.043 to 0.061, inc. Over 0.023 to 0.043, incl.
0..023 and tthinner
To 32, incl. 0.016 0.014 0.012 0.010 0.008 0.006
Over 32 to 0.016 0.016 0.012 0.010 0.008 0.006
40, incl.
Over 40 to 0.018 0.016 0.012 0.010 0.008 0.006
60, incl.
Over 60 to 0.018 0.018 0.012 0.010 0.008 —
72, incl.
NOTE: For width, length and camber tolerances, refer to ASTM A653.
58
SURFACE FINISHES:
»
The hot dip galvanizing process results in a zinc coating with a crystalline structure that Is clearly visible on the zinc surface. This is called a 'spangled
finish*. Typically, the spangled finish has a <»«tinrt surface relief caused by the spangle boundaries, dearly signifying that the desired "galvanized"
coating is present. For some applications. especially when the sheet wlU be painted, the spangled pattern may be undesirable frr reasons of appearance
or complete paint coverage at the spangle boundaries. If so, the size of the spangles can be controlled.
Here are some of the more common surfaces available:
Regular Spangle Galvanized Sheet - Has a pattern that occurs from normal hot-dip processing. These large, bright spangles are clearly visible. They
provide the readily-recognized, attractive surface finish of galvanized sheet. Regular spangle finish has a discernible amount of surface relief.
Suppressed Spangle Galvanized Sheet - Is similar to regularspangle except that It exhibits less surface relief. Also, the spangle size may be gmpifar. it is
specifically Intended for processing as pre-palnted galvanized sheet. The flatness of the spangle and the concomitant less distinct boundaries between
spangles enhance the ability of the sheet to be processed through paint lines without paint skips or blisters.
Minimum Spangle Galvanized Sheet - Has a finish in which the spangles are very small and have much less surface relief. Typically, this finish provides
a good surface for application of paint when minimal spangle show-through is desired. In addition, the reduced amount of surface relief allows more
complete paint coverage (leas tendency for paint skips).
Extra Smooth Galvanized Sheet • Whien a very uniform, smooth, matte finish is required, such as for critical exposed surfaces, regular, minimum and
suppressed spangle galvanized sheet can be furnished with an extra smooth finish. The most common finish combination is minimum spangle/extra
smooth. This special surface is produced by a separate temper rolling operation after coating. Its appearance resembles the matte finish of uncoated cold
rolled sheet. The use of extra smooth galvanized sh\:et Is required when spangle show-through after painting is unacceptable.
Now let's move to variations on surface treatments. NOTES:
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Steel Service Center Institute •
SURFACE TREATMENT:
Moat galvanized sheet can be specified with five variations of surface treatment:
• Chemical Treated Dry (Chemical Treatment Dry)
• Chemical Treated Oiled (Oil)
• Non-chemical Treated Dry
• Non-chemical Treated Oil
• Phosphatlzed
CHEMICAL TREATMENT:
"Chemical treatment" consists of the application of a thin, relatively invisible. corrosion-Inhibiting film on the zinc surface. This film Is applied on the
galvanizing line by dipping in (or spraying on) an aqueous solution of corrosion- inhibiting chemicals. The chemically treated surface is much more
resistant to humid-storage staining than an untreated galvanized surface. (This staining, sometimes called "white rust", Us simply the product of zinc
corroding in the presence of moisture.) Chemical treatment does a superior Job of:
• Preventing white rust in coils.
• Maintaining brightness and delaying the onset of darkening (graying)) of sheet surfaces upon exposure to the atmosphere.
However, chemical treatment is not compatible with most pre-treatments used on paint lines to produce pre-painted sheet because it interferes with
good adhesion of the paint. In most cases, sheet intended for subsequent painting should not be ordered with chemical treatment.
OIL:
Instead of chemical treatment, galvanized sheet can be ordered with "oil" to minimi** the tendency for humid storage stain. A thin coat of rust
preventive oil applied at the TP<H prevents white rust in colls and lifts during transit and short-team. h<gh humidity storage. Oil. unlike chemical
treatment, Is not intended to delay darkening of the spangled surface upon use. It Is generally less effective than chemical treatment as protection against
humid storage staining. Oil is very effective for preventing roll pick-up in roll forming operations. Often, oil is specified Instead of a chemical treatment
to protect the surface that subsequently will be painted. However, the sheet must b« thoroughly cleaned prior to painting.
CHEMICAL TREATMENT AND OIL:
A combination of "chemical treatment and olT can be spedfled when the effectiveness of the chemical treatment is desired for humid storage stain
resistance along with rust preventive oil for enhanced formability. Application of oil over the chemical treatment generally does not significantly
improve the humid storage stain resistance.
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DRY:
Galvanized sheet is shipped "dry* if neither daemlcal treatment nor oil is compatible with the customer's requirements. Untreated zinc surfaces are
susceptible to humid storage stain. Moisture intrusion or condensation during shipment or storage will cause white rust Galvanized sheet produced dry
must be transported and stored with special precautions to preserve low humidity conditions.
PHOSPHATIZED:
Any galvanized sheet surface finish such as regular spangle, suppressed spangle, or minimum spangle, can be "phosphatlzed". This product is specially
pre-treated at the mill for subsequent painting in the as-received condition. The treatment produces a relatively thick, dense, crystalline deposit of
hydrated ztoc phosphate compounds on the galvanized surface, resulting in a dull gray appearance,. This phosphate coating provides a good adherent
base for subsequent application of paint. Also, it offers added protection against undercutting of the paint film when corrosion is present.
Phasphatized galvannealed sheets are ready for immediate painting with many paints readily available from industrial and retail supplies. Specific
recommendations should be obtained from the paint manufacturer to insure that the paint used is compatible with the surface. Minor cleaning may be
necessary Co remove oils or soilage picked up during fabrication or handling. Phosphatlzed sheets, mill phosphatlzed to add extremely good paint-
adhering qualities to aH the good features of galvanized steel, greatly improve the life expectancy of the paint applied to them. They are recognizable by
their dull surface, marked with a white streak when scratched by a fingernail. If these sheets become oily or greasy, the surface should be cleaned with
mineral spirits, paint thinner, or naphtha.
Fingerprints should be removed with 50 percent mixture of one of the above thinners in combination with alcohol. Mill phosphatlzed sheets that have
been exposed to humid storage conditions or stored for long periods of time may require pTe-baktng for several minutes at about 300°F to prevent
blistering of baked finishes. A trial sheet can be painted to determine the need for a pire-bake. In addition, the phosphate alone may not be adequate to
guarantee against peeling of some very sensitive alkyd paints when exposed in highly humid environments. In such case, the use of a suitable primer
such as zinc-dust or epoxy or epoxy-ester base paint is recommeraded.
SURFACE INSPECTION:
Surface blemishes peculiar to galvanized sheet steel are sometimes encountered. Among the most common are zinc stringers, coarse coating, and zinc
ridges. When zinc adherence is good, and proper coating weights are present these surface blemishes have no harmful effect on the life of the sheet.
Two 'terms' should be explained:
-Whit* Rust - A zinc oxide formed by a combination of wetness with zinc. -Peeling - The detachment of ztoc coating from the base metal at the zinc
steel Interface.
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Steel: Service Center Institute <
FEATURES AND BENEFITS OF i HOT DIP GALVANIZED
Features
Galvanizing is one of the most economical coating processes for corrosion protection.
Galvanized sheet steel offers versatility in the construction and manufacturing fields. Galvanized sheet Is formable and weldable. It can be drawn, brake-
formed. roD-formed. or lock-formed.
When suitably prepared (sometimes phosphatized). galvanized sheet steel accepts a broad variety of coatings for pre-finlshing or post finishing.
Galvanized sheet steel increases service life for soils and wet concrete without concern for alkaline conditions, making it an excellent choice for
applications such as culvert pipe, floor and roof deck, Quonset huts and swimming pool liners.
Benefits
Saves replacement costs.
Long life and low fabricating costs.
No costly
preparation
costs.
Again, saves replacement costs.
NOTES:
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Now. tome information on fabricating of hot dipped galvanized. These areas con be mart heitful to customers who don't know how to weld, Join, paint,
etc. (Makes excellent FAX materiaL)
FORMING:
Hot dipped galvanized sheet can be formed almost as readily as uncoated cold rolled sheet of equivalent quality. It can be formed in a variety of ways,
from simple roll flbrming and brake pressing to complex and intricate stamping.
As with uncoated steel sheet, factors other than metallurgical quality (CQ. DQ-. DQSK. SQ or PQ, LFQ) of the base sheet enter Into the successful
forming of galvanized sheet. The galvanized coating exhibits friction characteristics that are different froan those of uncoated steel. Thus, lubricants, die
materials and other elements of fabrication must be compatible with the coating to optimize productivity. In stamping and forming* operations. It is
advantageous to use dies that are harder and smoother than would be -used for the same uncoated steel sheet. When proper attention has been given to
farming parameters, hot dipped galvanized sheet is essentially as formable as uncoated sheet of comparable metallurgical quality.
JOINING:
SOLDERING:
Soldering is an established method forjolnlng galvanized sheet or attachlrag solderable items to galvanized coatings. Galvanized sheet can be readily
soldered with many types of conventional solders and flux. Lead/tin solder alloys are typically used. FHux residues should be removed after soldering to
prevent corrosive damage to the zinc creating.
WELDING:
Galvanized sheet can be readily welded by the resistance, arc and cocyfuel gas welding processes, usually with the same equipment used to weld the
uncoated underlying steel. In the case of the arc and oxyfuel gas processes, precautions must be talken to avoid porosity and cracking of the weld caused
by penetration of zinc Into the weld pool.
Zinc has a lower melting point (787»F) than steel, and a lower boiling point (abtout ISBOF). During welding, zinc vapor bums in the air to produce
dense, white zinc oxide ffumes which require adequate ventilation. Specific precautions are given In ANSI Publication Z49.1 Safety fri Welding and
Cutting. The thicker the zinc coating, the more furmes that are generated. In general, resistance welding is preferred forjoininggalvanized shieet products
because It results In less fuming that other types of welding.
NOTES:
Steel Service Center Institute •
ELECTRIC RESISTANCE WELDING:
• »
Spot Welding - Because the galvanized coating has a lower surface contact resistance than bare steel, welding conditions for galvanized sheet win differ
somewhat from those used for welding uncoated sheet Generally, lilgher electrode forces and higher welding currents and/or longer weld-cycle times are
required to produce the same fused-zone diameter In galvanized sheet as in uncoatedl sheet. In addition, yfrx* pick-up on the electrodes causes fairly
rapid electrode wear, mo that only several thousand welds can be made before electrode dressing. To mlraftntee zinc pick-up, electrodes should be kept
as cool as possible by controlling the welding rate and utilizing water cooling. The use of copper alloy, truncated-cone-shaped electrodes is preferred for
spot welding galvanized sheet Dome-type electrodes also may be used when electrode alignment is a problem.
For all galvanized products, extremely high welding current is to be avoided because excessive heating tends to cause expulsion of the zinc coating under
the electrodes. The optimum set of welding parameters must be determined by trial and are dependent on the specific application and sheet
characteristics such as thickness or coating weight. (Galvannealed sheet is easier to weld than galvanized sheet.)
Seam Welding • Conventional seam weldfcng equipment can be used for welding lap joints in galvanized steel sheet. Seam welding of galvanized steel
sheet can be considered to be continuous spot welding; the .guidelines for spot welding should be followed for wm welding. To produce acceptable
welds, tlie procedures used for uncoated sh«et should be modified toward slightly narrower electrode width, higher electrode force, higher welding
current and slightly lower welding speed. These variables should be adjusted to produce welds of about the same size as welds in uncoiated sheet.
RESTORATION OF WELD AREAS:
When good appearance and maximum corrosicon resistance are desired in tlie weld area, oxides and fluxes from the welding operatlora may be removed
by sand blasting, wire brushing or grinding. Satisfactory recoating methods are soldering, metal spraying or application of metallic-plgm—ited paints.
FASTENERS:
From a mechanical standpoint, any style of fastener suitable for use with sheet metal can be used to join galvanized sheet to Itself or to otlher materials,
provided the fastener design is appropriate for the structural requirements, of the application. The list -of acceptable devices includes common fasteners
like nuts amd bolts, screws and rivets of all types, and special types like damp fasteners, clips and bind screws.
The fastener material should be carefully considered from two standpoints. First, the fastener should be equally as corrosion resistant as the galvanized
sheet to ensure long life of the fabricated product. Second, the fastener material should be compatible with the coating: that is. it should be selected to
avoid accelerated corrosion caused by intimate
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contact between certain types of d<*
metals. Suitable materials Include nylon or
other plastics, stainless steels and carbon steel fasteneas with thick zinc alloy heads. Galvanized or other plated fasteners also are suitable, "but the
coating must be thick enough so that the corrosion resistance Is compatible with that of the galvanized sheet.
Fasteners made of kad or copper dramatically accelerate the corrosion of the zinc when an electrolyte Is present The materials set up an electrolytic cell,
and the zinc coating sacrifices itself to protect the fasteners. Therefore, these fasteners must be avoided.
.ADHESIVE BONDING:
Adhesive bonding Is a relatively new. completely viable technique for fastening coated steel sheet to other coated or uncoated sheet and to other
materials. The growing use of adhesive bonding In the automotive Industry is demonstrating the reliability, durability and economy of this fastening
method.
Adhesive bonding effectively Joins dissimilar steel sheet products. It does not alter ttie properties of the steel or Its coating. It provides uniform stress
distribution and reduces vibration and noise. Adhesive bonding can serve to erahance product design, so that mechanical fasteners and/or welding can be
avoided. It can function as a moisture sealant. Also. It increases the range of material choices and material combinations available to the product designer.
Two important conditions are necessary for proper use of adhesive bonding: ( 1) The load on the bonded area should be evenly distributed: (2) The
Joint should be stressed mairaly in shear or tension while peel and cleavage forces should be minimal
Two types of adh;slves. thermosets and thermoplastics, are widely used to Join steel sheet. Thermos* ts generally possess high shear strength, rigidity
and durability, and are capable of supporting a wide range of specified design laads. They Include acrylics, epoxles, urethanes. cyanoacrylates and
anaerobics. Thermoplastics generally are tough aaid ductile, and are excellent for energy-absorbing applications. They include vinyl plastisols and hot
melts.
Because adhesrves can be chemically tailored to meet specific performance criteria, thiey provide the user with a Joining technique that Is capable of
satisfying a wide variety of manufacturing end-use requirements. For more information about adheslves for specific applications, consult an adhesive
manufacturer.
SEALANTS;
Sealants are often used between overlapping areas of steel sheet to form watertight Joints and to achieve superior environmental durability. Neutral-cure
slllcone rubber sealants are recommended for use with galvanized sheet. These materials need no primer. They are flexible and non-corrosive, as well as
resistant to tieat, cndd. water and ultraviolet rajrs.
Other types of sealants, like butyl rubber and styrene butadiene rubber, may also be used successfully. For more Information about sealants for specific
applications, consult a sealant manufacturer.
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Steel Sendee Center Jnstituts-
PAflVTDVO;
Galvanized sheet can be readily painted either before or alter fabrication. Paint provides obvious aesthetic effects, as well as Increased corrosion
protection. When the surface Is property pre-treated. and the appropriate paint system la selected, the pre-treatment forms an adherent bond between
the paint and the galvanized surface. A key to good performance Is selection and use of a primer designed for galvanized surfaces.
Galvanized parts should be thoroughly cleaned and dried prior to treatment. The usual pre-painting treatments are either phosphate or chromate
solutions (hot or cold). Whether or not a pre-treatment is used, a primer coat especially formulated for use on galvanized sheet should be applied.
Many types of paint can be used on galvanized sheet. The choice depends on the ultimate service requirements of the product. For example, some types
will maximize weather resistance, while others will provide a high gloss surface. Consultation with paint suppliers Is strongly recommended to obtain
maximum performance.
Now for some tips on storing and handling.
Galvanized steel sheets weather excellently and. In normal exposures, both Indoors and outdoors, afford long-time protection against corrosion.
Constant contact with moisture, however, may cause localized discoloration. This may occur, for example, when colls or bundles of cut lengths become
wet in transit and the moisture Is entrapped. The resulting discoloration Is known as "wet storage stain".
Although the "stain" is usually superficial, the loss of zinc minimal, and does not impair the effectiveness of the zinc coating. It may spoil the
appearance of the finish. In such cases, this stain can be removed with commercial cleaners. TSP - Trt Sodium Phosphate - is a common cleaner. The use
of an acid must be avoided. All chemical type cleaning methods win discolor or darken the original bright zinc luster.
To inhibit wet storage stain, producers treat their galvanized sheets chemically during processing when so ordered. As an alternate, where oil does not
interfere with the use of the sheets, galvanized steel sheets can be ordered oiled for protection against stain. Still, prolonged exposure to moisture can
cause localized damage. The answer is to keep the galvanized sheets dry by taking the following precautions:
1. Specify suitable packaging to protect the product while in transit.
2. Inspect for moisture on receipt. If moisture Is present, dry at once. For added protection during subsequent storage, a light film of oil may be applied
If desired. Do not store covered with plastics.
3. Do not permit moisture to remain between the sheets, laps of colls, or nested formed sections when stored In warehouses or In the field prior to use.
In some fabricating plants, hydrometers are Installed, and a routine check is made on the relative humidity of warehouse atmospheres. When the relative
humidity increases to a critical level, room heaters are turned on to avoid condensation. ClrcuUite air around material with fans.
Stetl Service Center Institute -
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4. Store !n a warm, dry place. For formed roofing and siding, stand on end on wood strips, or blocks, with sheets separated to allow moisture to drain
off and air to circulate.
APPLICATIONS FOR GALVANIZED SHEETS;
For applications in which corrosion resistance is a prime service requirement; Air-conditioning equipment ash cans; automotive bodies, brackets, frames,
and hardware: building panels: display cases: dryers: electrical boxes and outlets: farm buildings, equipment, and machinery: flooring: freezers: furniture:
garbage cans: guard rails: hardware: heating equipment; lighting fixtures: mailboxes: outdoor signs: playground equipment: railroad automotive-transport
cars, boxcars, hopper cars and reefers: radio equipment: ranges; refrigerators: roofing and siding: tackle boxes; tape recorder and television equipment:
textile equipment: toolboxes: trash cans; vending machines: wall panels; washers.
MISCELLANEOUS INFORMATION:
Galvanized Sheet Thickness and Weight Equivalents
Thickness Theoretical Thickness Theoretical
Equivalent Weight Equivalent Weight
(Inch) (Pounds Per (Inch) (Pounds Per
Sq. Ft.) Sq.FU
0.1681 6.858 0.0366 1.493
0.1532 6.251 0.0336 1.371
0.1382 5.639 0.0306 1.248
0.0276 1.126
0.1233 5.031 0.0247 1.008
0.1084 4.423
0.0934 3.811 0.0217 0.885
0.0785 3.203 0.0202 0.824
0.0710 2.897 0.0187 O.763
0.0172 0.702
0.0635 2.591 0.0157 0.641
0.0575 2.346
0.0516 2.105
0.0456 1.860
0.0396 1.616
TMW is based on 40.80 pounds per square foot, one Inch thick. To obtain the TMW of any decimal thickness, multiply the thickness equivalent
decimal by 40.80 to get the theoretical weight.
NOTES:
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Steel Service Center Institute •
QUALITIES:
The same as for galvanized hot-dip.
Commercial Quality (CQ)
Drawing Quality (DQ)
Drawing Quality Special Killed (DQSDKJ
Lock Forming Quality (LFQ)
Structural (Physical) Quality (SQ or PQ)
High Strength-Low Alloy (HSLA)
MECHANICAL PROPERTIES:
The mechanical properties are the same as the properties of regular galvanized sheet.
COATINGS:
GaJvannealed sheet Is produced typically to A40 and A60 coating designations by the ASTM A-525 designation system, and to metric coating
designations as Indicated in the following table. Since galvannealed sheet is designed to be pa'nted, these coating weights provide the necessary corrosion
resistance for most ^ product applications. If coated sheet Is to be exposed without paint protecfJcr, regular galvanized sheet should be used.
NOTES:
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Steel Service Center Institute-
COATING WEIGHTS
A. Customary Units
ASTM 525 Coating Designation
Minimum Coating Weight 02./sq. feet
A60 A40
Triple Spot Average
0.60 0.40
Single Spot
0.50 0.30
B. Metric Units
Coating Categories Minimum Coating Weight1 g/sqm
A20/20 A40/4O A50/50 A60/60 A70/70 A90/90 A98/98 20 4O 50 60 9O 98
(1) The weight of coating in oz. per sq. ft. refers to the total coating on both surfaces. Typically, about half this coating is on each side. The coating
designation number is the term by which this product Is specified. The triple spot average encompasses an edge-center-edge sampling to determine
adequate coverage across the sheet width.
(2) Ordered coating weight Is specified on a per-sldc basis, e.g. 50/50 requires each surface to have a minimum weight of 5O g/mj.
NOTES:
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QALVANTfEALED PRODUCTS
FEATURES
BENEFITS
B Corrosion Resistant
Long life, saves replacement costs.
Excellent Palntabillty
Easy Weldability
No time or material costs to prepare for painting.
Less labor and scrap.
IDEAS ON FABRICATING GALVANNEALED SHEETS FORMING
Galvannealed sheet can be formed In much the same manner and by the same variety of processes as galvanized sheet, since the steel substrate is
generally the same for both materials.
Although the steel fonnabillty is similar for both types of coating, there are differences In the forming behavior of the gaJvannealed and galvanized
coatings. The zlrk>alloy coating is more brittle than the zinc coating of galvanized sheet. When the sheet is bent or formed severely, the zinc-alloy
coating may powder on the compression side of the formation. This powdering Is not detrimental to corrosion resistance, but can cause "dirt" build-up
in die forming operations.
JOINING
Soldering
The Iron-zinc alloy of galvannealed sheet is substantially more difficult to solder than galvanized sheet, although soldering can be accomplished to
commercial production operations. Often, methods such as the use of more reactive fluxes are sufficient to make soldering easier.
Welding
Galvannealed sheet can be readily welded by the resistance, arc and cocyfuel gas processes, usually with the same equipment used to weld galvanized
sheet or the uncoated underlying steel. As with galvanized steel, precautions must be taken to avoid porosity and parking of the weld caused by
penetration of zinc into the weld pool while using the arc and cocyfuel processes. ANSI safety procedures also apply to this product.
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In electric resistance welding, such as spot welding, the zinc-iron alloy coating In similar thickness requires less welding current than regu'ar galvanized
coatings, resulting In longer electrode tip life. The coating reacts less with electrodes, which means less zinc pick-up, less redressing of electrodes and
more spot welds between redressing. Similar benefits will "be realized during seam welding of galvannealed sheet
Fasteners
Galvannealed sheet can be joined by the same fasteners and techniques as those applicable to galvanized sheet.
Adhesive Bonding \
\
Galvannealed sheet requires the same materials and pripcedures for bonding as hot-dip galvanized sheet. 1
PAINTING I
Galvannealed sheet Is an Ideal material for painted product applications. In high-volume opertlons. parts made of galvannealed sheet can be painted by
the same systems used to paint uncoated carbon steel. Whereas zinc coatings generally should be pre-treaied before painting, the zinc-alloy coating of
galvannealed sheet can be directly painted: however. Improved performance will be attained if a primer Is applied prior to the topcoat. Furthermmore,
the somewhat rougher finish of the zinc-alloy surface finish provides better mechanical bonding than the usually smoother surface finish of a galvanized
coating. In sen-ice, the galvannealed coating normally Is less reactive than zinc at sheared edges and other breaks in the paint.
Galvannealed sheet can be readily painted using many types paints. Typically, the surface should be cleaned after fabrication so that application of a
suitable primer and topcoat can achieve good paint adhesion and corrosion resistance. When a pre-treat-ment Is used to optimize resistance to corrosion
and paint fillm ^lamination, iron phosphate is recommended. As with paint systems for galvanized sheet, consultation with paint suppliers is strongly
recommended.
TYPICAL APPLICATIONS FOR GAT.VAIWKALED SHEETS
The excellent corrosion resistance that results when the alloyed coating is painted Is useful In many applications that demand long service life. For
example, painted galvannealed sheet provides excellent service when used on automobiles for both exposed and unexposed applications. It Is also
specified for buses, trucks, and other vehicles where long life is Important: garage doors: highway signs; vending machines; air conditioner covers; wall
partitions; cabinets; commercial refrigerators.
NOTES;
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Steel Service Center Institute <
Two Types • Hot Dipped
ElectrJLytic
HOT DIPPED GALVANIZE
Two Types
• Zendzimir
Cooke – Nortemari
GALVANIZE PRODUCT
Advantages:
• Corrosion Protection
• Fonnab le
• Paintable
Disadvantages:
• Weldability
GALVANNEAL PRODUCT
Advantages:
• Corrosion Protection
*
• Paintable
• Weldable
Disadvantages:
• Less Formable
• Lead Times
MINIMUM SPANGLE
Produced Two Ways
• Steam
Zinc Dust (Heurtey)
CHEMICAL TREATMENTS
Chrornate (passivation) Phosphate
COATING COMPARISONS
PRODUCT
Galvanize
Galvanneal
Electrogalvanize
Galvalume
Aluminum (Type 1)
Aluminum (Type 2)
COATING 99.5% Zinc 99.5% Zinc 100% Zinc
55% Aluminum 45% Zinc
95% Aluminum 5% Silicon
100% Aluminum
EXHIBIT #1 - Coatings for Steel Sheet Products
Types of Coatings
Description
I. Hot Dip Zinc Coated
Regular and Minimized Spangle
I This product Is made on continuous hot dip galvanizing lines and is supplied In colls and cut lengths.
The product includes regular and minimized spangle In a wide range of coating designations (ASTM A525/A525M) and is available In extra smooth
finish.
2. Hot Dip Zinc Coated
Fully Alloyed Zinc-Iron Coated
Hot-dip zinc coated product that is heat treated or wiped to produce a fully alloyed zinc-iron coating.
3. Hot Dip Zinc Coated Differentially Zinc Coated
Hot-dip zinc coated product that is produced with different specified coat-Ing weights on opposite sheet surfaces — being significantly lighter on one
surface. Both surfaces zinc.
4. Hot Dip Zinc Coated
Differentially Zinc-Iron Coated
Same as Coating #3 excettt the coating on the lighter surface is ;.eat treated or wiped to produce a fully alloyed zinc-iron coating.
5. Hot Dip Zinc Coated (One Side)
This product is produced with a continuous hot dip zinc coating on one side of the sheet and a zinc free, cold rolled steel surface on the other for
superior paintabllity.
6. Electrolytic Zinc Flash Coated
Electrolytic zinc coated steel is produced by continuously flash electroplating with zinc — 3 grams to 6 grams per square meter total on both sides. It Is
used when minimal corrosion resistance is required.
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Types of Coatings
Description
7. Electroplated Zinc Coated
Produced by continuously electroplating zinc. Two aide coatings can be produced on an equal basis for differentially total coating. One aide product has
a standard cold rolled surface. Generally 2 side coatings have a 140 g/ma.
8. Electropla:. J Iron Zinc Alloy Coated
Thl» product Is produced by the simultaneous electroplating of zinc and Iron to form an alloy coating. One and two side coatings can be produced on an
equal basis or differentially coated.
9. Electroplated Zinc NickeJ Alloy Coated
10. Aluminum Coated
11. Aluminum
Zinc Coated (GALVALUME)
12. Zinc-Aluminum/
Mischmetal Coated (GALFAN)
• This product is produced by the simultaneous electroplating of zinc and nickel to form an aBoy coating. One and two side coatings can be produced on
an equal basis or differentially coated.
• Aluminum coated 3teel Is produced by hot itiip coating cold rolled sheet steel on continuous lines. It provides a material with the superior strength of
steel and the surface properties of aluminum.
• Aluminum-zinc alley coated steel is produced by hot dip coating cold rolled sheet steel on continuous lines. It has the superior strength of steel and
excellent corrosion resistance, plus heatt resistance.
• Coaled steel is produced by hot-dip coating on continuous lines. It provides excellent formablllty and excellent corrosion resistance.
13. LongTeme
• Colcd rolled sheet steel Is coated on both sides with a lead-tin alloy by a continuous hot dip proce&s.
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Steel Service Center Institute •
Types of Coatings
Description
14. Nickel Teme
Cold rolled sheet steel electrolytically nickel flash plated and then coated on both sides with a lead-tin alloy by a continuous hot dip process. Corrosion
resistance is superior to standard long terne.
15. Tin Coated
16. Ztncrometal*
Cold rolled sheet steel coated with tin by a continuous electrolytic process.
A cold rolled sheet product with a base coat containing primarily chromium and zinc, top coated by a weldable zinc rich primer for corrosion resistance,
generally to only one side, with the other side being a standard cold rolled surface for superior paintabllity.
17. Coll Coated (Pre-Palnted)
A carbon steel sheet Is first coated wtth a metallic coating for protection and then coil-line painted.
NOTES:
Steel Senrice Center Institute •
14
TV&^'$&^- Main Applications
• Zinc-Coated Sheets • Hot-dip zinc-coated Building exterior materiads, ducts, corrugated pipe, household electrical appliances, dvil engineering
products, automotive pairts. light-gauge shapes, interior matte-rials.
• Hot-dip iron-zinc alloyed Shutters, doors, household efiec-trtCSll 3T7T?iJC3nCC3 8Ut CjniOtlVC OftlffS*
interior materials.
• Hot-dip zinc -aluminum alloy-coated Building exterior materials, dvil engineering products, auitomo&fcre parts, household electrical apgtfi-
ances.
• Electrolytic zinc-coated Doors, sashes, automotive pants, household electrical appliances.
hi Electrolytic zinc alloy-coated Automotive parts, household elkc-tncal appliances.
• Hot-dip alumlnlzed sheets Combustion equipment, muffleers. exhaust pipes, exterior materials.
• Terne-coated sheets Gasoline tanks, chassis fbrTVstets. radiators.
• Tlnplate Food cans, general cans. 18-1 cans, crown caps, aerosol cans
• Organic-Coated Sheets • Prepalnted hot-dip zinc-coated Roofs, sidings. Interior materUals, temporary works, outer panelssfor appliances.
• Prepalnted hot-dip zinc-aluminum alloy-coated Roofs, sidings.
NOTES:
22
CONTINUED...
Types
Prepalnted electrolytic zinc-coated
Decorative sheets (Embossed, pattern-printed, specially finished, high-grade decorattve-nnlshed)
Precoated
Weldable precoated PVC-coated Plastic - Laminated
Main Application*
Outer panels for appliances, interior materials.
Sidings. Interior materials, storm doors, household electrical appliances.
Interior and exterior materials, household electrical apspliances.
Outer panels for appliances, building materials, automotive parts.
Hoofs, sidings, anterior materials, outer panels for appliances.
Interior and exterior materials, kitchen utensils, household electrical appliances.
CORROSION.. Ji COMPLEX PHENOMENON:
Corrosion takes many forms. It can be uniform, spreading over the entire exposed surface of a metal sheet: or it can be localized, occurring where special
conditions create a corrosive agent. It can be microscopic or, more often In the case of steel sheet, macroscopic or clearly visible.
In addition to uniform corrosion, there are several osther types of visible corrosion. Examples include crevice corrosion which occurs wlthta flssvnres
and narrow openings where water may be trapped — at gaskets, lap Joints, bolts, rivets, weldments or scratches, for example. Poultice corrosion is
common on vehicles* occurring when mud cakes up inside wheeJwells and crevices. The mud retains road saJt and water and acts to keep the metal
surface damp, promoting corrosive chemical action. Erosstve corrosion occurs when an abrasive stream of water strikes a metallic surface. Still another
form of corrosion, known as fretting, occurs when mating surfaces are subjected to seepage of an electroryte solution In combination with vibration.
These four form* of corrosion are illustrated on the following page. NOTES:
23
Steel Sertice C«nter Institute •
severe for almost any application of steel sheet in the add rain regions and where sulfur dioxide and chloride levels are high.
Coated steel sheet properly selected and applied, can combat corrosion successfully in many applications. A metallic or organic coating can protect steel
sheet from corrosive attack by acting as a barrier to exclude air. water and other corrosion promotes* from contact with the sheet AD coatings — zinc,
zinc-aluminum. zinc-Iron, teme and paints — provide excellent barrier protection.
In addition to barrier protection, zinc and zinc alloys have the ability to react to scratches and other damage through an electrochemical (galvanic) action
between steel arad zinc. This galvanic action makes It possible for the zinc to protect breaks In the coatlmg and prevent further damage.
What all of these fundamentals are meant to Illustrate Is the complexity of our suibject, and the need for this manual. We will provide a great deal of
informatlc.i. broken Into areas by the type of basic coatings: Zinc. Aluminum. Lead and Tin, Paint. We win examine within each coating type the
methods of affixing the coatings, base metal qualities, coating weights available, features and benefits of the products, and other useful data.
The idea of this manual is not to make you a metallurgist, but to supply you wttti a source of facts and information. The first places to look for answers
are the Tabfle of Contents and the Glossary of Terms.
NOTES:
25
S ieel Service Center Institute -
OF PRODUCING COATED SHEET PRODUCTS
We have the base metal, now how do the producers of coated products applj the various coatings? Hot dipping, electrolytic and coll coating for painted
products are the three basic methods.
HOT DIP PROCESS:
Typically, the hot dip process begins with an as-cold-reduced or pre-armealed steel sheet especially selected for coating. As the sheet Is uncoiled. It Is
cleaned, because a clean surface Is essential to develop a good bond between the steel and the coating. On many lines, an electrolytic cleaning unit
subjects the sheet to a combination of fast-flowing alkaline solution and electrical current for efficient removal of oils, lubricants and other surface
contaminants. Brushes remove any vestige of remaining soil as the sheet passes through scrubber units. After hot water rinsing, the sheet Is completely
dried by rubber-squeegee rolls and hot air.
The cleaned sheet then goes through a continuous-annealing furnace where at Is given either a high-temperature or pre-heac anneal to prepare it for
coating. When a significant change In mechanical properties is desired, the high-temperature cycle la usedL In this cycle, the steel is heat-treated in a
precision-controlled, oxygen-free atmosphere to provide the different strength and formabllity levels required by customer applications. The furnace is
divided into zones to allow exact control of temperatures for heating, holding and cooling the sheet as it acquires desired mechanical properties. When
either minimal or no changes in mechanical properties are desired, the steel goes through the preheating cycle. When the sheet leaves the continuous-
annealing furnace, the surface is fuDy prepared to accept a smooth, even coating.
Immediately after furnace preparation, the sheet enters the coating bath. The continuously moving sheet Is immersed in a bath of molten met-J. The
coating comocsltlora and processing temperatures are rigorously controlled to achieve the optimum bond between coating and steel.
A unique feature of the hot dtp process ts that the coating forms an adherent, fntermetoi-Uc bond with the steel substrate, so that the coating and the
steel behave as one during fabrication and service.
As the steel exits the coating bath, a thin, molten layer of the coating metal adheres, to both sides of the sheet. The sheet passes between a set of air
knives where air Is directed under pressure against the strip to regulate the thickness of the molten coating and achieve closely controlled, uniform
coating thickness.
The molten coating solidifies as the sheet moves vertically through the cooling toweT. The solidification process is controlled to Impart selective surface
finishes, such as minimized spangle, to the coating.
Steel Service Center Institute <
39
A CAUTIONARY NOTE:
It Is important to note that the amount of coating of zinc or zinc-iron coating is the prime reason customers buy galvanized products. The method of
applying the zinc to the base or substrate metal Is of secondary importance.
Using modem day systems, both hot dip and electrolytic coating methods are acceptable to most customers. If they Insist on one or the other, you
might question why. and of course know what you carry in stock.
And finally, a key for you in answering "Which of these products should I buy?", can be a variation of "What do you manufacture? What process do
you use?"
End use! As always the key to providing the customer with the product they need.
NOTES:
Steel Service Center Institute •
43
JVOTES:
Steel Sendee Center Institute •
different methods of coating base metals. These methods are reviewed in the "Methods of Coating* section. But here Is a quick explanation of each:
The hot dip process consists of passing the steel through a both of molten zinc. The electroplating process consists of the application of zinc by
electrolytic disposition.'
What we will do In the first section Is to treat hot dtp galvanized, then follow with the data on electrolytic galvanized sheets...and then gahrannealed
Base Metals (For all galvanized products): • The most common base metal for
galvanized sheets Is cold-rolled steel. Occasionally, hot-rolled will be specified. (The ASTM specification for such products will be ASTM A-568.)
NOTES:
45
Steel Service Center Institute •
HOT-DIP ZINC COATED GALVANIZED STEEL SHEET
WHAT IS IT?
A carbon steel sheet, coated with zinc on both sides of the sheet, by the continuous hot dip process. The process results in a zinc layer tightly adhering
to the base steel through an iron-zinc bonding layer. (Note: If an iron-zinc alloy is wanted, then you need galvannealed! We will discuss galvannealed
later.)
It should be noted that the standard specification for zinc-coated (galvanized) steel sheets by the hot-dip process is ASTM A653.
HOW IS IT PRODUCED?
By the continuous hot-dip process. For full details and schematic, refer to the section of "Methods of Coating".
Base Metals - Cold rolled or hot rolled steel sheets (occasionally high strength - low alioy.x, Steels - As you will see, there are six principal steels. All
are covered by ASTM A653.
Hot-dip galvanized sheet is produced in six principal steels: Commercial Steel (CS Types A, B and C) Forming Steel (FS Types A and B) Deep
Drawing Steel (DOS) Extra Deep Drawing Steel (HDDS) Structural Steel (SS) High Strength Low Alloy Steel (HSLAS Types A and B)
GALVANIZED COMMERCIAL STEEL - CS - (ASTM A653):
Ordinarily produced from rimmed, capped, semi-killed, or continuously cast steel. This steel! is generally suitable for simple bending, mild drawing and
roll forming. The customer normally furnishes information on the individual requirements of the identified part.
Sheets should stand bending at room temperature flat on themselves in any direction without fracture of the base metal. If greater ductility than the
minimum indicated by the bend test is required, or if uniformity of properties is necessary, DDS or HDDS will fill the requirements. (See DOS or
HDDS).
The zinc coating should stand bending without flaking when tested in accordance with provi sions of ASTM A653.
46
Commercial Steel can be processed after coating to improve the smoothness of surface or to control the temper.
This steel can be supplied with reasonably consistent non-fluting characteristics at the time of shipment. However, with lime, aging can occur with loss
oj ductility and return oj flailing characteristics. Fluting can be minimized by roller leveling immediately prior to fabrication.
When stretcher strains are objectionable on parts made from galvanized Commercial Steel, then temper rolled or extra smooth should be specified. Aging
will bring about reduced ductility and a return of the tendency to stretcher strain. Effective roller leveling immediately before fabrication, depending on
storage time, may eliminate or minimize strain.
Coils and cut lengths are identified as Commercial Steel or CS by showing this designation or symbol on each shipping tag. When a coating designation is
specified, it is als« shown on each shipping unit.
The quality can be specified to ASTM A653, "Steel Sheet Zinc-Coated (Galvanized) by the Hot-Dip Process. Commercial Steel."
CHEMICAL COM POSITION
CHEMICAL REQUIREMENTS
ELEMENT % TYPE A % TYPE B % TYPE C
CARBON, MAX 0.10 0.02-0.. 15 0.08
MANGANESE, MAX. 0.60 0.60 0.60
PHOSPHORUS, MAX. 0..030 0.030 0.100
SULFUR, MAX. 0.035 0.035 0.035
COPPER, WHEN SPECIFIED, MIN 0..20 0.20 0.20
47
GALVANIZED FORMING STEEL - FS (ASTM-A653):
Produced from specially processed steel and is processed to have good uniform form ing and drawing properties for use in fabricating parts having
severe deformations.
The primary difference between FS and CS sheet is that FS sheet is more ductile. FS sheet is typically used for applications where breakage (splitting)
would be encountered with CS sheet. FS sheet is produced from specially selected steels, processed for improved and more uniform formability
properties.
Forming and drawing operations must be carefully controlled by the user to provide the required performance. FS sheet is subject to the same aging
phenomenon as CS sheet; therefore, to avoid strain lines, FS sheet should be roller leveled just before the forming operation..
The steel is not commonly specified as to chemical composition, and is generally tfurnished for use in fabricating an identified part too difficult for the
fabricating properties of galvanized commercial steel.
The customer normally furnishes information on the individual requirements of an idlentified part.
There are no established standards with respect to the flaking of coating during fabrication; hence, care should be taken to ensure that the coating
designation is compatible with the end application involved.
Forming Steel is not ordinarily processed to control the phenomenon kn*own as stretcher strains.
When stretcher strains are objectionable on parts made from galvanized Forming Ste:el, temper rolled or extra smooth should be specified. Aging will
bring about reduced ductility and a return of the tendency to stretcher strain. Effective roller leveling immediately before fabrication, depending on the
storage time, may eliminate or minimize stretcher straining.
Delays between draws may detrimentally affect the properties of the steel.
Coils and cut lengths are identified as Forming Steel or FS by showing this designation or symbol on each shipping unit. When a coating designation is
specified, it is also shown on each shipping unit.
Sheet steel of this grade can be specified to ASTM A653, "Steel Sheet, Zinc-Coated (Galvanized by the Hot-Dip Process Forming Steel)."
48
ASTM A653 FORMING STEELS: (Continued)
This steel is intended for fabricating identified parts which involve forming or drawing beyond the requirements of commercial quality. These sheets
nnay also be susceptible to aging with lime and are sold on the basis of chemistry without certified mechanical properties. Forming steel is not intended
for those applications that require good drawing properties.
Material supplied under this specification shall meet the applicable requirements of the latest revision of Specification A653 unless otherwise specified.
CHEMICAL COMPOSITIONS
CHEMICAL REQUIREMENTS
ELEMENT TYPE A TYPEB
CARBON 0.10 MAX. 0.02/0.10
MANGANESE 0.50 MAX. 0.50 MAX.
PHOSPHORUS 0.020 MAX. 0.020 MAX.
SULFUR 0.035 MAX. 0.030 MAX.
GALVANIZED DEEP DRAWING STEEL (DPS) AND EXTRA DEEP DRAWING STEEL (EDDS)
Generally a low carbon aluminum killed steel, although the producer sometimes uses other deoxidizers to obtain the proper characteristics.
These steels are not commonly specified to chemical composition and are generally furnished for use in fabricating an identified part where draw or
forrraation is particularly severe or where the material is to be essentially free from significant changes in mechanical properties over a period of time.
The customer normally furnishes information on the individual requirements of the identified
part.
DOS & EDDS should be specified where the formed material! is to be essentially free of such surface disturbances as stretcher strains or fluting without
the need of prior roller leveling.
There are no established standards with respect to the flaking of coating during fabrication; hence, care should be taken to ensure that the coating
designation is compatible with the end application involved.
49
Material supplied under this specification shall meet the applicable requirements of the latest revision of Specification A653 unless otherwise specified
herein.
CHEMICAL COMPOSITIONS
CHEMICAL REQUIREMENTS
ELEMENT DOS EDDS
CARBON 0.06 MAX. 0.02 MAX
MANGANESE 0.50 MAX. 0.40 MAX
PHOSPHORUS 0.020 MAX. 0.020 MAX.
SULFUR 0.025 MAX. 0.020 MAX.
ALUMINUM 0.01 MIN. 0.01 MIN.
GALVANIZED STRUCTURAL STEEL SS (ASTM A-653):
Produced when mechanical properties are specified or required other than that indicated by the base metal bend test of commercial quality. Such
properties or values include those indicated by tension, hardness or other commonly accepted mechanical tests. For most applications, only one kind of
test requirement is normally applied. Hardness tests are made on specimens stripped of coating. Tension tests are usually made in accordance with
ASTM A653.
SS sheet is recommended for applications in which specific mechanical properties are required for strength in a finished part, usually in load-bearing
structures. Orders for SS usually require that minimum yield and tensile strengths or a minimum hardness value (Rockwell B) be met by the steel
producer. When specified minimum yield strength is 35 ksi or greater, Structural Steel sheet is classified as high strength sheet. When specifying an SS
grade, the user should carefully consider the compatibility of the specified properties with forming requirements. In general, steels produced to meet
increasing yield strength levels have a corresponding decrease in ductility or formability.
Normally, the formability of Structural Steel sheet decreases with increasing yield strength and/or hardness. Therefore, for the proper and economical
utilization of Structural Steel sheet, product design should be considered by the consumer.
Structural Steel is ordinarily furnished with the sulfur content up to 0.040 percent by heat
analysis.
Coils and cut lengths are identified as Structural Steel or SS by showing this designation or symbol on each shipping unit. When a coating designation is
specified, it is also shown on each shipping unit. Sheet steel is commonly specified to ASTM A653, "Steel Sheet, Zinc-Coated (Galvanized) by the Hot-
Dip Process, Structural Steel."
50
CHEMICAL REQUIREMENTS
DESIGNATION COMPOSITION % (MAX)
SS GRADE CARB. MANG. PHOS. SULF.
33 0.20 ..... 0.04 0.04 :
37 0.20 ..-. 0.10 0.04
40 0.25 .... 0.10 0.04
50 CL 1 & 2 0.40 ..„. 0.20 0.04 ;
50CL3 0.50 ..... 0.04 0.04
80 0.20 ..... 0.04 0.04
HSLASTYPEA
50 0.20 1.20 •••• 0.035
60 0.20 1,35 • ••• 0.035
70 0.20 1,65 ..*. 0.035
80 0.20 1,65 .... 0.035
HSLAS TYPE B
50 0.15 1.20 *.*• 0.035
60 0.15 1.20 .... 0.035
70 0.15 1.65 .... 0.035
80 0.15 1.65 *••• 0.035
Where an ellipsis (....) appears there is no requirement, but the amalysis shall be reported.
Steel conforming to this designation commonly contains the stremgthening elements columbium, nit.Togen, phosphorus or vanadium, added singly or in
combination
Some steels may be treated by means of small alloy additions to effect sulfide inclusion control.
51
MECHANICAL REQUIREMENTS
BASE METAL (LONGITUDINAL)
DESIGNATION TYPE GRADE Y.S. MIN./KSI T.S. MIN./KSI %EL MIN./2"
SS .... 33 33 45 20
37 37 52 18
40 40 55 16
50CL1 50 65 12
50CL2 50 .... 12
50CL3 50 70 12
80 80 82 ....
HSLAS TYPE A 50 50 60 20
60 60 70 16
70 70 80 12
80 80 90 10
HSLAS TYPEB 50 50 60 22
60 60 70 18
70 70 80 14
80 80 90 12
NOTE 1 - If the hardness result is 85 HRB or higher, no tension'test is required. NOTE 2 - Where an ellipsis (....) appears in this table there is no
requirement.
52
The next chart shows "typical"mechanical properties
TYPICAL MECHANICAL PROPERTIES FOR HOT-DIP PRODUCT
DESIGNATION YIELD TENSILE %EL Rb
CS - TYPE A 20/50 38/60 20MIN 4€/70
CS - TYPE B 30/60 43/65 20MIN 45/70
CS - TYPE C 20/50 40/60 20MIN 40/73
FS - TYPE A 20/45 35/50 30MIN 30/60
FS - TYPE B 25/45 38/55 25MIN 35/65
DDS 20/35 35/50 32MIN 32/55
EDDS 15/25 32/45 40MIN 30/44
53
COATINGS:
As staled, one of the most important aspects of galvanized products is the coating thickness. Measured as coating weight in ounces per square foot or
grams per square meter, it is an important factor in the effective application of galvanized sheet. The coating weight should be chosen carefully, with full
attention to the fabrication method and type of environment im \\hicli the sheet will be expected to serve. In general, the effectiveness of the zinc coating
to protect the steel substrate from corrosion in any given environment is directly proportional to the coating thickness. For example, for any specific set
of environmental conditions, a G90 coating will last about 50 percent longer than a G60 coating - maintenance, painting and all other factors being equal.
Factors in addition to corrosion resistance must be considered when selecting coating thickness. For example, tthe adherence of the coating generally is
inversely proportional to the thickness; therefore, a thin coating is more desirable for applications involving high amounts of forming. Also, spot welding
becomes more difficult as the coating thickness
increases.
The weight of coating may be specified as a coating designation or as a minimum coating test limit such as the striple spot or single spot test. The
methods of sampling and testing follow the provisions of American Society for testing and Material (ASTM) Specification A653. The weight of the
coating is the total amount on both sides of a sheet, expressed in ounces per square foot of sheet, or in the metric system grams per square meter.
COATING DESIGNATION AND MINIMUM COATING TEST LIMITS (ASTM A653)
INCH - POUND UNITS OZ/FT
TYPE COATING DESIGNATION TOTAL BOTH SIDES ONE SIDE TOTAL BOTH SIDES
ZINC G360 3.260 1.28 3.20
G300 3 00 1.04 2.60
G235 2.35 0.80 2.00
G2IO 2.10 0.72 1.80
GI85 1 .85 0.64 1.60
G165 1 .65 0.58 1.40
G140 1 .40 0.48 1.20
G115 1 .15 0.40 1.00
G90 01.90 0.32 0.80
G60 0.60 0.20 0.50
G40 0.40 0.12 0.30
G30 O.30 0.10 0.25
G01 NO MIN NO MIN NO MIN
ZINC-IRON A 60 0.60 0.20 0.50
A 40 10.40 0.12 0.30
A 25 '0.25 0.08 0.20
A01 NO MIN NO MIN NO MIN
NOTE I The weight of coaling in ounces per square foot refers to the ttotal coaling on both surfaces. The coauing designation numiber is the term b\
which this product is specified.
54
(NOTES CONTINUED)
NOTE 2: As it is an established fact that the atmospheric corrosion resistance of mill galvanized sheet product is a direct function of coating weight
(thickness), the selection of lighter coating designations will result in almost nearly reduced corrosion performance of the zinc coating. For example, the
heavier galvanized coatings perform adequately in bold atmospheric exposure, whereas the lighter weight coatiings are often further coated with paint or
similar barrier coating for increased corrosion resistance. Because of this relationship, products carrying the statement, "meets ASTM A653
requirements" should also specify coating weight designation.
COATING DESIGNATORS:
G = Free Zinc
A = Zinc-Iron Alloy (Galvannealed)
X = No Coating, i.e. - one side (Metric)
E = Exposed Part (metric)
U = Unexposed Pan (Metric)*
Ni = Nickel
A WORD OF EXPLANATION ON COATING WEIGHTS:
A G90 coating means that the material is a hot-dip galvanized product, with a minimum coating weight (triple spot average).
The triple spot average covers an edge-center-edge sampling to determine adequate coverage across the sheet width. To convert coating weight from oz.
/sq. ft. to g./sq.m., the following factor cam be used: g./sq.m. = oz./sq.ft. x 305.15
Note that although a precise conversion between ASTM A653 "G" categories (G30, G60, etc.) and the metric categories (20/20, 40/40, etc.) cannot be
made, a G60 coating category (ASTM A653) is approximately equal to a 90/90 coating category (metric).
NOTE: A "U" after an "ounce per square foot", means the product is (G90) UL approved.
55
TYPES OF COATINGS
One Side Coated - Has a specified coating designation on one surface for corrosion protection and the other surface being tree of coating that will be
suitable for painting. The coating side normally has a spangled appearance. It is commonly produced to an equivalent coating weight of G60 or G90.
Extra Smooth or Temper Rolled - Is furnished when a higher degree of surface smoothness is required than is normal for as-coated galvanized or to
minimize flatting or stretcher straining. There may be variations in the coating practices and types of coat employed, but the extra smooth product is
always temper rolled. Some loss in ductility is associated with temper rolling.
Extra smooth galvanized in coils or cut lengths may contain slight coating imperfections which can be removed with a reasonable amount of light metal
finishing.
A WORD OF EXPLANATION ON COATINGS:
Zinc has a lower melting point (787 degrees F) than steel, and a lower boiling point (about 1660 degree F). During welding, zinc vapor burns in the air to
produce dense, white zinc oxide fumes which require adequate ventilation. Specific precautions are given in ANSI Publication Z49.1 Safety in Welding
and Cutting. The thicker the zinc coating, the more fumes that are generated. In general, resistance welding is preferred for joining galvanized sheet
products because it results in less fuming than other types of welding.
NOTES:
56
BEND TESTING:
ASTM A653
Coating Bend Test Requirements * For ES, FS, DOS and EDDS
Ratio of Bend Diameter to Thickness of Specimen (any direction)
Galvanized Sheet Thickness
Coating Designation 0.1 756 in to 0.0748 in. 0.0747 in. to 0.0382 in. 0.0381 in. to 0.0131
G235 3 3 2
G210 2 2 2
G185 2 2 2
G165 2 2 2
G140 2 1 1
G115 1 0 0
G90 1 0 0
G60 0 0 0
G01 0 0 0
* This table does not apply to Structural Steel and Alloy Coatings.
NOTE: For Structural Steel (SS) and High Strength Low Alloy Steel (HSLAS) Bend Test Requirements refer to ASTM A653.
57
THICKNESS:
ASTM A653
Thickness Tolerances of Hot-Dip Galvanized Sheet
NOTE 1: Thickness is measured at any point across the width not less than 3/8 in. from a siide edge.
NOTE 2: The specified thickness range captions noted below also apply when sheet is specified to a nominal thickness and the below tolerances are
divided equally, over and under.
Thickness Tolerances for Widths and Thicknesses, Tolerances all over - none under
Specified Thickmess, in..
Specified Width, In. Over 0.101 to 0.1 87, incl. Over 0.075 to 0.101, inc. OverO.(061 to 0.015, inc. Over 0.043 to 0.061, inc. Over 0.023 to 0.043, incl.
0..023 and tthinner
To 32, incl. 0.016 0.014 0.012 0.010 0.008 0.006
Over 32 to 0.016 0.016 0.012 0.010 0.008 0.006
40, incl.
Over 40 to 0.018 0.016 0.012 0.010 0.008 0.006
60, incl.
Over 60 to 0.018 0.018 0.012 0.010 0.008 —
72, incl.
NOTE: For width, length and camber tolerances, refer to ASTM A653.
58
SURFACE FINISHES:
»
The hot dip galvanizing process results in a zinc coating with a crystalline structure that Is clearly visible on the zinc surface. This is called a 'spangled
finish*. Typically, the spangled finish has a <»«tinrt surface relief caused by the spangle boundaries, dearly signifying that the desired "galvanized"
coating is present. For some applications. especially when the sheet wlU be painted, the spangled pattern may be undesirable frr reasons of appearance
or complete paint coverage at the spangle boundaries. If so, the size of the spangles can be controlled.
Here are some of the more common surfaces available:
Regular Spangle Galvanized Sheet - Has a pattern that occurs from normal hot-dip processing. These large, bright spangles are clearly visible. They
provide the readily-recognized, attractive surface finish of galvanized sheet. Regular spangle finish has a discernible amount of surface relief.
Suppressed Spangle Galvanized Sheet - Is similar to regularspangle except that It exhibits less surface relief. Also, the spangle size may be gmpifar. it is
specifically Intended for processing as pre-palnted galvanized sheet. The flatness of the spangle and the concomitant less distinct boundaries between
spangles enhance the ability of the sheet to be processed through paint lines without paint skips or blisters.
Minimum Spangle Galvanized Sheet - Has a finish in which the spangles are very small and have much less surface relief. Typically, this finish provides
a good surface for application of paint when minimal spangle show-through is desired. In addition, the reduced amount of surface relief allows more
complete paint coverage (leas tendency for paint skips).
Extra Smooth Galvanized Sheet • Whien a very uniform, smooth, matte finish is required, such as for critical exposed surfaces, regular, minimum and
suppressed spangle galvanized sheet can be furnished with an extra smooth finish. The most common finish combination is minimum spangle/extra
smooth. This special surface is produced by a separate temper rolling operation after coating. Its appearance resembles the matte finish of uncoated cold
rolled sheet. The use of extra smooth galvanized sh\:et Is required when spangle show-through after painting is unacceptable.
Now let's move to variations on surface treatments. NOTES:
65
Steel Service Center Institute •
SURFACE TREATMENT:
Moat galvanized sheet can be specified with five variations of surface treatment:
• Chemical Treated Dry (Chemical Treatment Dry)
• Chemical Treated Oiled (Oil)
• Non-chemical Treated Dry
• Non-chemical Treated Oil
• Phosphatlzed
CHEMICAL TREATMENT:
"Chemical treatment" consists of the application of a thin, relatively invisible. corrosion-Inhibiting film on the zinc surface. This film Is applied on the
galvanizing line by dipping in (or spraying on) an aqueous solution of corrosion- inhibiting chemicals. The chemically treated surface is much more
resistant to humid-storage staining than an untreated galvanized surface. (This staining, sometimes called "white rust", Us simply the product of zinc
corroding in the presence of moisture.) Chemical treatment does a superior Job of:
• Preventing white rust in coils.
• Maintaining brightness and delaying the onset of darkening (graying)) of sheet surfaces upon exposure to the atmosphere.
However, chemical treatment is not compatible with most pre-treatments used on paint lines to produce pre-painted sheet because it interferes with
good adhesion of the paint. In most cases, sheet intended for subsequent painting should not be ordered with chemical treatment.
OIL:
Instead of chemical treatment, galvanized sheet can be ordered with "oil" to minimi** the tendency for humid storage stain. A thin coat of rust
preventive oil applied at the TP<H prevents white rust in colls and lifts during transit and short-team. h<gh humidity storage. Oil. unlike chemical
treatment, Is not intended to delay darkening of the spangled surface upon use. It Is generally less effective than chemical treatment as protection against
humid storage staining. Oil is very effective for preventing roll pick-up in roll forming operations. Often, oil is specified Instead of a chemical treatment
to protect the surface that subsequently will be painted. However, the sheet must b« thoroughly cleaned prior to painting.
CHEMICAL TREATMENT AND OIL:
A combination of "chemical treatment and olT can be spedfled when the effectiveness of the chemical treatment is desired for humid storage stain
resistance along with rust preventive oil for enhanced formability. Application of oil over the chemical treatment generally does not significantly
improve the humid storage stain resistance.
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DRY:
Galvanized sheet is shipped "dry* if neither daemlcal treatment nor oil is compatible with the customer's requirements. Untreated zinc surfaces are
susceptible to humid storage stain. Moisture intrusion or condensation during shipment or storage will cause white rust Galvanized sheet produced dry
must be transported and stored with special precautions to preserve low humidity conditions.
PHOSPHATIZED:
Any galvanized sheet surface finish such as regular spangle, suppressed spangle, or minimum spangle, can be "phosphatlzed". This product is specially
pre-treated at the mill for subsequent painting in the as-received condition. The treatment produces a relatively thick, dense, crystalline deposit of
hydrated ztoc phosphate compounds on the galvanized surface, resulting in a dull gray appearance,. This phosphate coating provides a good adherent
base for subsequent application of paint. Also, it offers added protection against undercutting of the paint film when corrosion is present.
Phasphatized galvannealed sheets are ready for immediate painting with many paints readily available from industrial and retail supplies. Specific
recommendations should be obtained from the paint manufacturer to insure that the paint used is compatible with the surface. Minor cleaning may be
necessary Co remove oils or soilage picked up during fabrication or handling. Phosphatlzed sheets, mill phosphatlzed to add extremely good paint-
adhering qualities to aH the good features of galvanized steel, greatly improve the life expectancy of the paint applied to them. They are recognizable by
their dull surface, marked with a white streak when scratched by a fingernail. If these sheets become oily or greasy, the surface should be cleaned with
mineral spirits, paint thinner, or naphtha.
Fingerprints should be removed with 50 percent mixture of one of the above thinners in combination with alcohol. Mill phosphatlzed sheets that have
been exposed to humid storage conditions or stored for long periods of time may require pTe-baktng for several minutes at about 300°F to prevent
blistering of baked finishes. A trial sheet can be painted to determine the need for a pire-bake. In addition, the phosphate alone may not be adequate to
guarantee against peeling of some very sensitive alkyd paints when exposed in highly humid environments. In such case, the use of a suitable primer
such as zinc-dust or epoxy or epoxy-ester base paint is recommeraded.
SURFACE INSPECTION:
Surface blemishes peculiar to galvanized sheet steel are sometimes encountered. Among the most common are zinc stringers, coarse coating, and zinc
ridges. When zinc adherence is good, and proper coating weights are present these surface blemishes have no harmful effect on the life of the sheet.
Two 'terms' should be explained:
-Whit* Rust - A zinc oxide formed by a combination of wetness with zinc. -Peeling - The detachment of ztoc coating from the base metal at the zinc
steel Interface.
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FEATURES AND BENEFITS OF i HOT DIP GALVANIZED
Features
Galvanizing is one of the most economical coating processes for corrosion protection.
Galvanized sheet steel offers versatility in the construction and manufacturing fields. Galvanized sheet Is formable and weldable. It can be drawn, brake-
formed. roD-formed. or lock-formed.
When suitably prepared (sometimes phosphatized). galvanized sheet steel accepts a broad variety of coatings for pre-finlshing or post finishing.
Galvanized sheet steel increases service life for soils and wet concrete without concern for alkaline conditions, making it an excellent choice for
applications such as culvert pipe, floor and roof deck, Quonset huts and swimming pool liners.
Benefits
Saves replacement costs.
Long life and low fabricating costs.
No costly
preparation
costs.
Again, saves replacement costs.
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Now. tome information on fabricating of hot dipped galvanized. These areas con be mart heitful to customers who don't know how to weld, Join, paint,
etc. (Makes excellent FAX materiaL)
FORMING:
Hot dipped galvanized sheet can be formed almost as readily as uncoated cold rolled sheet of equivalent quality. It can be formed in a variety of ways,
from simple roll flbrming and brake pressing to complex and intricate stamping.
As with uncoated steel sheet, factors other than metallurgical quality (CQ. DQ-. DQSK. SQ or PQ, LFQ) of the base sheet enter Into the successful
forming of galvanized sheet. The galvanized coating exhibits friction characteristics that are different froan those of uncoated steel. Thus, lubricants, die
materials and other elements of fabrication must be compatible with the coating to optimize productivity. In stamping and forming* operations. It is
advantageous to use dies that are harder and smoother than would be -used for the same uncoated steel sheet. When proper attention has been given to
farming parameters, hot dipped galvanized sheet is essentially as formable as uncoated sheet of comparable metallurgical quality.
JOINING:
SOLDERING:
Soldering is an established method forjolnlng galvanized sheet or attachlrag solderable items to galvanized coatings. Galvanized sheet can be readily
soldered with many types of conventional solders and flux. Lead/tin solder alloys are typically used. FHux residues should be removed after soldering to
prevent corrosive damage to the zinc creating.
WELDING:
Galvanized sheet can be readily welded by the resistance, arc and cocyfuel gas welding processes, usually with the same equipment used to weld the
uncoated underlying steel. In the case of the arc and oxyfuel gas processes, precautions must be talken to avoid porosity and cracking of the weld caused
by penetration of zinc Into the weld pool.
Zinc has a lower melting point (787»F) than steel, and a lower boiling point (abtout ISBOF). During welding, zinc vapor bums in the air to produce
dense, white zinc oxide ffumes which require adequate ventilation. Specific precautions are given In ANSI Publication Z49.1 Safety fri Welding and
Cutting. The thicker the zinc coating, the more furmes that are generated. In general, resistance welding is preferred forjoininggalvanized shieet products
because It results In less fuming that other types of welding.
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ELECTRIC RESISTANCE WELDING:
• »
Spot Welding - Because the galvanized coating has a lower surface contact resistance than bare steel, welding conditions for galvanized sheet win differ
somewhat from those used for welding uncoated sheet Generally, lilgher electrode forces and higher welding currents and/or longer weld-cycle times are
required to produce the same fused-zone diameter In galvanized sheet as in uncoatedl sheet. In addition, yfrx* pick-up on the electrodes causes fairly
rapid electrode wear, mo that only several thousand welds can be made before electrode dressing. To mlraftntee zinc pick-up, electrodes should be kept
as cool as possible by controlling the welding rate and utilizing water cooling. The use of copper alloy, truncated-cone-shaped electrodes is preferred for
spot welding galvanized sheet Dome-type electrodes also may be used when electrode alignment is a problem.
For all galvanized products, extremely high welding current is to be avoided because excessive heating tends to cause expulsion of the zinc coating under
the electrodes. The optimum set of welding parameters must be determined by trial and are dependent on the specific application and sheet
characteristics such as thickness or coating weight. (Galvannealed sheet is easier to weld than galvanized sheet.)
Seam Welding • Conventional seam weldfcng equipment can be used for welding lap joints in galvanized steel sheet. Seam welding of galvanized steel
sheet can be considered to be continuous spot welding; the .guidelines for spot welding should be followed for wm welding. To produce acceptable
welds, tlie procedures used for uncoated sh«et should be modified toward slightly narrower electrode width, higher electrode force, higher welding
current and slightly lower welding speed. These variables should be adjusted to produce welds of about the same size as welds in uncoiated sheet.
RESTORATION OF WELD AREAS:
When good appearance and maximum corrosicon resistance are desired in tlie weld area, oxides and fluxes from the welding operatlora may be removed
by sand blasting, wire brushing or grinding. Satisfactory recoating methods are soldering, metal spraying or application of metallic-plgm—ited paints.
FASTENERS:
From a mechanical standpoint, any style of fastener suitable for use with sheet metal can be used to join galvanized sheet to Itself or to otlher materials,
provided the fastener design is appropriate for the structural requirements, of the application. The list -of acceptable devices includes common fasteners
like nuts amd bolts, screws and rivets of all types, and special types like damp fasteners, clips and bind screws.
The fastener material should be carefully considered from two standpoints. First, the fastener should be equally as corrosion resistant as the galvanized
sheet to ensure long life of the fabricated product. Second, the fastener material should be compatible with the coating: that is. it should be selected to
avoid accelerated corrosion caused by intimate
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contact between certain types of d<*
metals. Suitable materials Include nylon or
other plastics, stainless steels and carbon steel fasteneas with thick zinc alloy heads. Galvanized or other plated fasteners also are suitable, "but the
coating must be thick enough so that the corrosion resistance Is compatible with that of the galvanized sheet.
Fasteners made of kad or copper dramatically accelerate the corrosion of the zinc when an electrolyte Is present The materials set up an electrolytic cell,
and the zinc coating sacrifices itself to protect the fasteners. Therefore, these fasteners must be avoided.
.ADHESIVE BONDING:
Adhesive bonding Is a relatively new. completely viable technique for fastening coated steel sheet to other coated or uncoated sheet and to other
materials. The growing use of adhesive bonding In the automotive Industry is demonstrating the reliability, durability and economy of this fastening
method.
Adhesive bonding effectively Joins dissimilar steel sheet products. It does not alter ttie properties of the steel or Its coating. It provides uniform stress
distribution and reduces vibration and noise. Adhesive bonding can serve to erahance product design, so that mechanical fasteners and/or welding can be
avoided. It can function as a moisture sealant. Also. It increases the range of material choices and material combinations available to the product designer.
Two important conditions are necessary for proper use of adhesive bonding: ( 1) The load on the bonded area should be evenly distributed: (2) The
Joint should be stressed mairaly in shear or tension while peel and cleavage forces should be minimal
Two types of adh;slves. thermosets and thermoplastics, are widely used to Join steel sheet. Thermos* ts generally possess high shear strength, rigidity
and durability, and are capable of supporting a wide range of specified design laads. They Include acrylics, epoxles, urethanes. cyanoacrylates and
anaerobics. Thermoplastics generally are tough aaid ductile, and are excellent for energy-absorbing applications. They include vinyl plastisols and hot
melts.
Because adhesrves can be chemically tailored to meet specific performance criteria, thiey provide the user with a Joining technique that Is capable of
satisfying a wide variety of manufacturing end-use requirements. For more information about adheslves for specific applications, consult an adhesive
manufacturer.
SEALANTS;
Sealants are often used between overlapping areas of steel sheet to form watertight Joints and to achieve superior environmental durability. Neutral-cure
slllcone rubber sealants are recommended for use with galvanized sheet. These materials need no primer. They are flexible and non-corrosive, as well as
resistant to tieat, cndd. water and ultraviolet rajrs.
Other types of sealants, like butyl rubber and styrene butadiene rubber, may also be used successfully. For more Information about sealants for specific
applications, consult a sealant manufacturer.
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Steel Sendee Center Jnstituts-
PAflVTDVO;
Galvanized sheet can be readily painted either before or alter fabrication. Paint provides obvious aesthetic effects, as well as Increased corrosion
protection. When the surface Is property pre-treated. and the appropriate paint system la selected, the pre-treatment forms an adherent bond between
the paint and the galvanized surface. A key to good performance Is selection and use of a primer designed for galvanized surfaces.
Galvanized parts should be thoroughly cleaned and dried prior to treatment. The usual pre-painting treatments are either phosphate or chromate
solutions (hot or cold). Whether or not a pre-treatment is used, a primer coat especially formulated for use on galvanized sheet should be applied.
Many types of paint can be used on galvanized sheet. The choice depends on the ultimate service requirements of the product. For example, some types
will maximize weather resistance, while others will provide a high gloss surface. Consultation with paint suppliers Is strongly recommended to obtain
maximum performance.
Now for some tips on storing and handling.
Galvanized steel sheets weather excellently and. In normal exposures, both Indoors and outdoors, afford long-time protection against corrosion.
Constant contact with moisture, however, may cause localized discoloration. This may occur, for example, when colls or bundles of cut lengths become
wet in transit and the moisture Is entrapped. The resulting discoloration Is known as "wet storage stain".
Although the "stain" is usually superficial, the loss of zinc minimal, and does not impair the effectiveness of the zinc coating. It may spoil the
appearance of the finish. In such cases, this stain can be removed with commercial cleaners. TSP - Trt Sodium Phosphate - is a common cleaner. The use
of an acid must be avoided. All chemical type cleaning methods win discolor or darken the original bright zinc luster.
To inhibit wet storage stain, producers treat their galvanized sheets chemically during processing when so ordered. As an alternate, where oil does not
interfere with the use of the sheets, galvanized steel sheets can be ordered oiled for protection against stain. Still, prolonged exposure to moisture can
cause localized damage. The answer is to keep the galvanized sheets dry by taking the following precautions:
1. Specify suitable packaging to protect the product while in transit.
2. Inspect for moisture on receipt. If moisture Is present, dry at once. For added protection during subsequent storage, a light film of oil may be applied
If desired. Do not store covered with plastics.
3. Do not permit moisture to remain between the sheets, laps of colls, or nested formed sections when stored In warehouses or In the field prior to use.
In some fabricating plants, hydrometers are Installed, and a routine check is made on the relative humidity of warehouse atmospheres. When the relative
humidity increases to a critical level, room heaters are turned on to avoid condensation. ClrcuUite air around material with fans.
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4. Store !n a warm, dry place. For formed roofing and siding, stand on end on wood strips, or blocks, with sheets separated to allow moisture to drain
off and air to circulate.
APPLICATIONS FOR GALVANIZED SHEETS;
For applications in which corrosion resistance is a prime service requirement; Air-conditioning equipment ash cans; automotive bodies, brackets, frames,
and hardware: building panels: display cases: dryers: electrical boxes and outlets: farm buildings, equipment, and machinery: flooring: freezers: furniture:
garbage cans: guard rails: hardware: heating equipment; lighting fixtures: mailboxes: outdoor signs: playground equipment: railroad automotive-transport
cars, boxcars, hopper cars and reefers: radio equipment: ranges; refrigerators: roofing and siding: tackle boxes; tape recorder and television equipment:
textile equipment: toolboxes: trash cans; vending machines: wall panels; washers.
MISCELLANEOUS INFORMATION:
Galvanized Sheet Thickness and Weight Equivalents
Thickness Theoretical Thickness Theoretical
Equivalent Weight Equivalent Weight
(Inch) (Pounds Per (Inch) (Pounds Per
Sq. Ft.) Sq.FU
0.1681 6.858 0.0366 1.493
0.1532 6.251 0.0336 1.371
0.1382 5.639 0.0306 1.248
0.0276 1.126
0.1233 5.031 0.0247 1.008
0.1084 4.423
0.0934 3.811 0.0217 0.885
0.0785 3.203 0.0202 0.824
0.0710 2.897 0.0187 O.763
0.0172 0.702
0.0635 2.591 0.0157 0.641
0.0575 2.346
0.0516 2.105
0.0456 1.860
0.0396 1.616
TMW is based on 40.80 pounds per square foot, one Inch thick. To obtain the TMW of any decimal thickness, multiply the thickness equivalent
decimal by 40.80 to get the theoretical weight.
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Steel Service Center Institute •
QUALITIES:
The same as for galvanized hot-dip.
Commercial Quality (CQ)
Drawing Quality (DQ)
Drawing Quality Special Killed (DQSDKJ
Lock Forming Quality (LFQ)
Structural (Physical) Quality (SQ or PQ)
High Strength-Low Alloy (HSLA)
MECHANICAL PROPERTIES:
The mechanical properties are the same as the properties of regular galvanized sheet.
COATINGS:
GaJvannealed sheet Is produced typically to A40 and A60 coating designations by the ASTM A-525 designation system, and to metric coating
designations as Indicated in the following table. Since galvannealed sheet is designed to be pa'nted, these coating weights provide the necessary corrosion
resistance for most ^ product applications. If coated sheet Is to be exposed without paint protecfJcr, regular galvanized sheet should be used.
NOTES:
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Steel Service Center Institute-
COATING WEIGHTS
A. Customary Units
ASTM 525 Coating Designation
Minimum Coating Weight 02./sq. feet
A60 A40
Triple Spot Average
0.60 0.40
Single Spot
0.50 0.30
B. Metric Units
Coating Categories Minimum Coating Weight1 g/sqm
A20/20 A40/4O A50/50 A60/60 A70/70 A90/90 A98/98 20 4O 50 60 9O 98
(1) The weight of coating in oz. per sq. ft. refers to the total coating on both surfaces. Typically, about half this coating is on each side. The coating
designation number is the term by which this product Is specified. The triple spot average encompasses an edge-center-edge sampling to determine
adequate coverage across the sheet width.
(2) Ordered coating weight Is specified on a per-sldc basis, e.g. 50/50 requires each surface to have a minimum weight of 5O g/mj.
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QALVANTfEALED PRODUCTS
FEATURES
BENEFITS
B Corrosion Resistant
Long life, saves replacement costs.
Excellent Palntabillty
Easy Weldability
No time or material costs to prepare for painting.
Less labor and scrap.
IDEAS ON FABRICATING GALVANNEALED SHEETS FORMING
Galvannealed sheet can be formed In much the same manner and by the same variety of processes as galvanized sheet, since the steel substrate is
generally the same for both materials.
Although the steel fonnabillty is similar for both types of coating, there are differences In the forming behavior of the gaJvannealed and galvanized
coatings. The zlrk>alloy coating is more brittle than the zinc coating of galvanized sheet. When the sheet is bent or formed severely, the zinc-alloy
coating may powder on the compression side of the formation. This powdering Is not detrimental to corrosion resistance, but can cause "dirt" build-up
in die forming operations.
JOINING
Soldering
The Iron-zinc alloy of galvannealed sheet is substantially more difficult to solder than galvanized sheet, although soldering can be accomplished to
commercial production operations. Often, methods such as the use of more reactive fluxes are sufficient to make soldering easier.
Welding
Galvannealed sheet can be readily welded by the resistance, arc and cocyfuel gas processes, usually with the same equipment used to weld galvanized
sheet or the uncoated underlying steel. As with galvanized steel, precautions must be taken to avoid porosity and parking of the weld caused by
penetration of zinc into the weld pool while using the arc and cocyfuel processes. ANSI safety procedures also apply to this product.
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In electric resistance welding, such as spot welding, the zinc-iron alloy coating In similar thickness requires less welding current than regu'ar galvanized
coatings, resulting In longer electrode tip life. The coating reacts less with electrodes, which means less zinc pick-up, less redressing of electrodes and
more spot welds between redressing. Similar benefits will "be realized during seam welding of galvannealed sheet
Fasteners
Galvannealed sheet can be joined by the same fasteners and techniques as those applicable to galvanized sheet.
Adhesive Bonding \
\
Galvannealed sheet requires the same materials and pripcedures for bonding as hot-dip galvanized sheet. 1
PAINTING I
Galvannealed sheet Is an Ideal material for painted product applications. In high-volume opertlons. parts made of galvannealed sheet can be painted by
the same systems used to paint uncoated carbon steel. Whereas zinc coatings generally should be pre-treaied before painting, the zinc-alloy coating of
galvannealed sheet can be directly painted: however. Improved performance will be attained if a primer Is applied prior to the topcoat. Furthermmore,
the somewhat rougher finish of the zinc-alloy surface finish provides better mechanical bonding than the usually smoother surface finish of a galvanized
coating. In sen-ice, the galvannealed coating normally Is less reactive than zinc at sheared edges and other breaks in the paint.
Galvannealed sheet can be readily painted using many types paints. Typically, the surface should be cleaned after fabrication so that application of a
suitable primer and topcoat can achieve good paint adhesion and corrosion resistance. When a pre-treat-ment Is used to optimize resistance to corrosion
and paint fillm ^lamination, iron phosphate is recommended. As with paint systems for galvanized sheet, consultation with paint suppliers is strongly
recommended.
TYPICAL APPLICATIONS FOR GAT.VAIWKALED SHEETS
The excellent corrosion resistance that results when the alloyed coating is painted Is useful In many applications that demand long service life. For
example, painted galvannealed sheet provides excellent service when used on automobiles for both exposed and unexposed applications. It Is also
specified for buses, trucks, and other vehicles where long life is Important: garage doors: highway signs; vending machines; air conditioner covers; wall
partitions; cabinets; commercial refrigerators.
NOTES;
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Steel Service Center Institute <
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