Secondary Steel Tons and Tons
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Secondary Steel Tons and Tons

Galvanized and Galvannealed Steel Coils

Galvanized Steel Coil Slitting
Galvannealed Steel Coils

Galvanized is produced from Cold Rolled (or Hot Rolled Pickled & Oiled) coil that has been passed continuously through a pot of molten zinc. The amount of coating applied to the surface is controlled by wiping, rollers and/or air jets. The coated product is then cooled and passes through leveling equipment. The zinc coating protects the steel substrate in two ways. First, it creates a barrier that retards the formation of rust. Second, zinc has a self-sacrificial character and will extend itself to cover nearby small uncoated areas (i.e., cut edges, scratches).

There is generally a direct correlation between the amount of zinc application and the steel's atmospheric corrosion resistance. The more the zinc, the more the corrosion resistance. The amount of zinc (referred to as coating weight) is represented in ounces per square foot (or sometimes grams per square meter) total both sides. Its designation, for example, may be G60 (or A60, in the case of Galvannealed), constituting .60 oz/ft2. As such, the material would have approximately one-third less protection than G90 (.90 oz/ft2).

Galvanized (and Galvannealed) are typically produced in accordance with ASTM A653 standards and tolerances.

Zinc Coating Categories
Minimum Coating Wt. oz/ft2 Total Both Sides
DesignationTriple Spot TestSingle Spot Test
Both SidesOne Side
G60 or A60.60.20.50
G40 or A40.40.12.30
G30 or A30.30.10.25

Coating Weights

Coating weights are sometimes denoted in metric standards (SI units), grams per square meter each side. For example, category 60G/60G stipulates that each side has a minimum single spot coating weight of 60 grams per square meter (g/m2).

Essex Trading Company normally furnishes coating weight descriptions using single-spot testing per ASTM A90 standards.

US and metric conversion factors are:
1 oz/ft2 = 305.15 g/m2 · 1 g/m2 = 0.00328 oz/ft2
In terms of coating thickness, 1 oz/ft2 = 1.7 mils.

Coating Conversion Formula
Convert FromConvert ToMultiply By
ounces/square foot (oz/ft2)grams/square meter (g/m2)305.15
grams/square meter (g/m2)ounces/square foot (oz/ft2)0.00328


Coating Comparisons (Approx.)
Grams per Sq. Meter
Per Side
Grams per Sq. Meter
Both Sides
Ozs. Per Sq. Ft.
Both Sides (approx. equiv.)
98G/98G 196 G64
90G/90G 180 G59
70G/70G 140 G46
60G/60G 120 G39
50G/50G 100 G33
40G/40G 80 G26
20G/20G 40 G13
10G/10G 20 G07
5G/5G 10 G03


As the zinc solidifies during the coating process, snowflake or flower-like patterns ("spangle") emerge. Neither spangle appearance nor its size determines corrosion resistance.

Regular Spangle: Moderate-large (approx. 1/2" diameter) and usually bright/shiny

Minimum Spangle: Small (approx. 1/8" - 1/4" diameter) and usually bright/shiny

Zero Spangle (aka extra smooth): No visible spangle; generally duller than Regular or Minimum Spangle; usually intended for painted applications

Galvannealed: A form of hot-dipped galvanized consisting of an iron-zinc alloy coating on both sides. When the coil exits the zinc bath, the molten zinc coating is subjected to an in-line annealing (thus the name "Galvannealed") process that creates the zinc-iron alloy layer. The coating is denoted by an "A" designation (i.e., A60). It has a uniform light-medium gray color and a semi-porous finish that is easily paintable. Compared to regular hot-dipped Galvanized, it has similar corrosion resistance and a harder coating that is more resistant to scratching. Galvannealed tends to have somewhat less ductility and the coating sometimes powders (especially in heavier coating weight, i.e., A60) under severe forming.

Bonderized: A form of hot-dipped galvanized which has been phosphatized to promote paintability. Appearance is typically dark-grey and sometimes the underlying spangle pattern may be visible. Has same corrosion protection as regular galvanized, usually available in G60 and G90 coating weights. Bonderized's popularity has declined since the 1980s, having been replaced by Galvannealed for many applications.

Galvanized Base Metal Classifications

Commercial Steel (CS Types A,B,C), Forming Steel (FS), Deep Drawing Steel (DDS), Extra Deep Drawing Steel, Structural Steel (SS), High Strength Low Alloy (HSLA), Full Hard

Mechanical Properties
ClassificationYield Str. psiTensile Str. psiElong. % / 2"Rock. B typical
Commercial Steel (Type B)40000 typ.-- >20 typ.48
Forming Steel35000 typ.-->26 typ.38
Deep Drawing Steel28000 typ.48000 typ.>32 typ.34
Extra Deep Drawing Steel20000 typ.-->40 typ.30
Struct. Steel - Grade 3333000 min.45000 min.20 min.58
Struct. Steel - Grade 4040000 min.55000 min.16 min.65
Struct. Steel - Grade 50 Cl. 150000 min.65000 min.12 min.75
Struct. Steel - Grade 8080000 min.82000 min.--85
Full Hard70000 typ.90000 typ.--90
HSLA Grade 45 Cl. 145000 min.60000 min.25 min.65
HSLA Grade 50 Cl. 150000 min.65000 min.22 min.70
HSLA Grade 55 Cl. 155000 min.70000 min.20 min.75
HSLA Grade 60 Cl. 160000 min.75000 min.18 min.80
typ. denotes typical commercial; min. denotes minimum per ASTM standards

Structural Steel - Bending Properties
90° long. bend  ·  t = steel thickness
ClassificationMin. Inside Diameter
Grade 331½-t
Grade 402-t
Grade 50 Cl. 1not applicable
Grade 50 Cl. 2not applicable
Grade 80not applicable

Coating Bend Test Requirements
(ratio of inside bend diameter to thickness)
 CS, FS, DDS, EDDS Grd. 33Grd. 37Grd. 40Grd. 50Grd. 80
Sheet Thickness     
Coat. Wt..010"-.039".040"-.079".080"-.160"

Special Essex Features/Offerings

For especially-discounted pricing, we offer several products that are well suited for many building products (i.e., studs, framing components) and other noncritical appearance applications:

Mixed Coils: Having galvanized (bright) and galvannealed (dull) coatings. Little or no loss in corrosion resistance.

Pup Coils: Coils smaller than about 200 piw. Our savings often far outweigh any related increase in processing/production time.

Full Hard: For applications that are flat, require higher strength and/or little bending or forming.