Apr 05

A40 vs G60

I recently received a phone call asking me what the difference between the “A” and the “G” was when talking about hot dipped galvanized products.   And of course that spawned a quest for knowledge.  So here is what I learned about A40 vs G60 in case one day you’re asked the question.

And don’t forget my post on Galvanized vs Galvanneal for more information.  Please comment below if you have anything to add.

A vs G

Hot-Dipped Galvanized is produced to established minimum zinc coating weights in ounces per square foot. These coating weight will have a prefix of either “A” or “G” Generally “G” denotes a free zinc coating whereas “A” denotes a zinc/iron alloy coating.  The “G”, free zinc type, offers better corrosion resistance, but the “A”, alloy type, is more easily spot welded.

The corrosion resistance of the “G” type is directly related to the amount of zinc coating, i.e., G90 will resist corrosion to the base metal longer than G30.

The “A” coatings have a dull gray color with no spangle while the “G” coatings are bright/shiny and can have various sized spangle visible. This is the traditional galvanized appearance.

Hot-Dipped Galvanized can be chemically treated to inhibit the formation of zinc oxide or have a surface oil applied to retard storage stains. The “G” types are often coil coating with paint and are usually post formed by roll forming or embossing of the strip. Garage and entrance doors are examples of this practice. The “A” type is typically painted after all forming or bending is completed.

Both types, “A” and “G” are available on a full range of steel grades from CS (Commercial Steel) through EDDS (Extra Deep Drawing Steel). These grades have varying ability to be formed. Hot-Dipped Galvanized is produced to meet ASTM A 653 Specifications, “General Requirements for Steel Sheet Zinc Coated by the Hot-Dip Process”.

40 vs 60

Now, in reference to the number following the A or G refers to the amount of zinc 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.






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