A novel corrosion transformation process in aluminum alloy / galvanized steel welded joint

Replacing steel with aluminum alloy is appealing to realize the lightweight of metal structures. Novelis AC 170 PX aluminum alloy and ST06 Z galvanized steel sheets were lap welded by gas tungsten arc welding (GTAW) with ER4047 filler wire and the corrosion behavior of the joint was characterized. The results revealed that the zinc-rich zone had the highest corrosion susceptibility. The difference of localized corrosion between the adjacent area near the rod-shaped and the layered Fe4Al13 phases was explained by galvanic effect. When Zn in the zinc-rich zone was exhausted, the corrosion process of the joint was controlled by the second phases and corrosion products.