Effect of intermetallic compound on the corrosion behaviour of resistance spot welding joints between 5182 aluminium alloy and galvanized DP780 dual-phase steel

Abstract

Interfacial intermetallic compound (IMC) layer is critical during realizing the galvanic corrosion mechanism and strength degradation of aluminium/steel resistance spot welding (RSW) joints. The effect of IMC layer on the corrosion behaviour of RSW joint between 5182 aluminium alloy and galvanized DP780 dual-phase steel was investigated by immersion corrosion method and electrochemical method. Results demonstrated localized corrosion around Fe-rich phase particles on aluminium nugget and preferential corrosion at the interface front near IMC layer. The IMC layer had the highest open circuit potential value of −0.569 V and low corrosion current density among the investigated nugget and substrates. The potential difference (0.184 V) between the cathodic IMC layer and large area of anodic aluminium nugget was responsible for the preferential initiation of localized corrosion at the interface front near the IMC layer.