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.

Corrosion Behavior and Mechanical Property of 5182 Aluminum/DP780 Steel Resistance Spot Welding Joints

“…And, its corrosion seems not to be accelerated by the aluminum nugget because of the noble corrosion potential. This result is different from the general consideration that the IMC layer was mostly susceptible to corrosion damage due to the galvanic effect [18], but consistent with our previous research [20]. Such a different result may be due to the careful sample preparation from the fracture surface and the influence of the aluminum nugget could be avoided after the EDX reassurance.…”

“…Considering the IMC thickness within several micrometers and the residual galvanized layer, it is difficult to achieve the intrinsic corrosion property of the IMC layer by general electrochemical test from the joint cross-section. After thoroughly cleaning out the residual zinc contamination and ensuring by EDX, higher corrosion resistance of the interfacial IMC layer was actually evidenced by Zhang et al [ 20 ].…”

Effect of surface grinding on the microstructure and corrosion of Al-Mg-Si-Cu alloys

“…Corrosion behaviors of aluminum alloys are closely associated with IMPs, grain boundary precipitation, grain size and precipitate free zone. The electrochemical inhomogeneity of metallic material caused by intermetallic phases leads to the preferential dissolution of IMPs and/or adjacent matrix [37][38][39]. Initially, corrosion occurs at the site of defect on the surface, such as intermetallic particle.…”