Galvanic Corrosion Between Al‒Zn‒Mg‒Cu Alloy and Stainless Steel in the Salt-Spray Atmosphere

The galvanic corrosion between Al-Zn-Mg-Cu alloy and stainless steel in the salt-spray atmosphere was investigated based on experimental testing and the COMSOL simulation. The kinetic curves of the weight loss for the Al-Zn-Mg-Cu alloy specimens coupled with stainless steel and the monomer specimens basically follow a power function with an exponential of 0.33 and 0.38, respectively, and the weight loss of the former is three times that of the latter after corrosion for 128 h. According to the COMSOL simulation and coupling polarization curve, the potential and current density at the galvanic corrosion zone (GCZ) are-0.67 V and 13.6 A/m2, while those at the exposed corrosion zone (ECZ) are-0.82 V and 3 x 10-3 A/m2. The maximum width of the GCZ increases from 501 mu m to 1980 mu m when the corrosion time increases from 2 h to 128 h. The accelerated pitting corrosion due to the high current density created by Al-Steel coupling produced the large-sized corrosion pits at the GCZ (>= 200 x 200 mu m), much larger than the sizes of those at the ECZ (60 x 60 mu m). In addition, the galvanic corrosion process of Al-Zn-Mg-Cu alloy was elaborated.