Galfan (ZA) coatings are produced when a AHSS coil continuously runs through a hot-dip bath of 95% zinc and 5% aluminum. Compared to traditional zinc (GI) coatings, zinc-aluminum coatings have both superior forming properties and corrosion protection.
ZA coatings provide approximately twice the corrosion protection of hot-dip galvanizing (GI). “Galfan” is the coating’s registered trademark and EN 10346 standard refer to ZA, but most car manufacturers refer to this coating as zinc-aluminum or ZA, while ASTM uses GF.
The eutectic mix of 95% Zn and 5% Al produces a lamellar microstructure for improved adhesion and ductility. Compared to traditional pure zinc coatings, zinc-aluminum coated AHSS provides superior formability, making it well suited for deep drawing, roll forming, profiling, and bending. ZA-coated parts also have great resistance to cracking, delamination, and powdering due to the thin intermetallic layer at the substrate and coating interface.
Like other metal coatings, zinc-aluminum coated steels require slightly higher current and electrode force when spot welding due to the coating’s electrical resistance. However, if the automaker is able to reduce the thickness of the ZA coating — while achieving the same level of protection when compared to zinc galvanized — then both welding currents and electrode force can also be lower than for the thicker GI coating.
Many adhesives used for zinc-coated steels can also be used for zinc-aluminum coated steels. For mechanical joining of ZA steel, bolts, rivet tabs, and non-tabs methods can be used.
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