Galvannealed AHSS automotive steels

The iron content of the coating provides unbeatable resistance weldability, meaning longer electrode life together with low galling in forming. Galvannealed is designated by GA in the VDA 239-100 standard, ZF (for EN 10346:2015 standard) and A (for ASTM standards) and is informally known as a zinc-iron or hot-dip galvannealed (HDGA) coating.

Galvannealed coatings have a higher hardness than traditional zinc (GI) coatings, providing increased scratch protection during forming. GA coatings can lead to powdering, which can be minimized or eliminated by the proper forming set-up and by specifying thin Galvannealed coatings — which most automotive OEMs want anyway. GA coatings have good laser-cutting properties, which can reduce your laser cutting costs.

In general, Galvannealed-coated steels are considered optimal for the resistance welding of corrosion-resistance AHSS steels. Compared to traditional zinc (GI) coatings, galvannealed coatings allow a much larger range in welding currents. With lower welding currents, GA coatings allow for longer electrode service life. With the correct welding parameters, GA welded joints are comparable to those on uncoated AHSS.

Galvannealed AHSS can be joined using a variety of appropriate adhesives. As with all adhesive processes, protective oils and chemical treatments may need to be removed prior to bonding. Mechanical joining can be accomplished via bolts, rivet tabs, and non-tabs.