Corrosion Failure Analysis of AA5083 Connected With Al‐Zn‐In‐Cd Anode in Simulated Seawater Level Fluctuation Zone

The water level fluctuation zone (or alternating wet and dry environment) is a typical service condition for marine aluminum alloys (AAs). The mechanism by which cathodic protection affects the corrosion of AAs in this environment remains to be clarified. In this study, the corrosion behavior of AA5083 (connected with an Al‐Zn‐In‐Cd sacrificial anode) in a simulated water level fluctuation zone was investigated using electrochemical impedance spectroscopy (EIS) combined with surface and cross‐sectional morphology observation. The localized and uniform corrosion of AA5083 in the water level fluctuation zone is accelerated after coupling with the Al‐Zn‐In‐Cd anode. This is mainly because, under wet conditions, the sacrificial anode causes the protection potential to be excessively negative, and the hydrogen evolution reaction on the electrode surface dominates. This leads to the alkalization of the electrode surface, a reduction in the thickness of the oxide film, and thus accelerates the corrosion of the alloy matrix.