Galvannealed steel product summary

About the steel retainers used in our aircraft hangar door weatherstripping solutions

Galvannealed is a form of hot-dipped galvanized sheet consisting of an iron-zinc alloy coating on both sides. It is produced from Cold Rolled coil (or Hot Rolled Pickled & Oiled typically thicker than 14-gauge) that has been passed continuously through a pot of molten zinc. The coating amount applied to the surface is controlled by wiping, rollers and/or air jets. When the coil exits the zinc bath, the molten zinc is subjected to inline annealing (thus the name “Galvannealed”) that forms the zinc-iron alloy layer. It is subsequently run through leveling rolls for shape correction. The coating is denoted by an “A” designation, i.e., A60 (as opposed to regular Galvanized denoted with a “G” prefix, i.e., G60).

Galvannealed has a uniform light-medium gray color and a semi-porous finish. Galvannealed is especially intended for painting applications. Compared to regular hotdipped Galvanized, it has similar corrosion resistance and a harder coating that is more resistant to scratching. Galvannealed tends to have slightly less ductility and the coating sometimes powders (especially in heavier coating weight, i.e., A60) under severe forming. As in regular hot-dipped Galvanized, 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 selfsacrificial 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 usually represented in ounces per square foot (or sometimes grams per square meter) total both sides. For example, its designation may be A40, constituting .40 oz/ft2. As such, the material would have approximately one-third less protection than A60 (.60 oz/ft2).

Generally, Galvannealed has become the preferred product of automobile, appliance and many other OEMs and fabricators, given the product’s excellent paintability, and lower cost compared to Electrogalvanized. Since the 1980s, it has almost completely supplanted Bonderized (phosphatized).

Galvannealed (like hot-dipped Galvanized sheet) is typically produced in accordance with ASTM A653 standards and tolerances.