Corrosion Behavior of 6061 Aluminum Alloy in Simulated SO2-Polluted Seawater

The corrosion behavior of 6061 aluminum alloy in 3.5 wt.% NaCl solution with different NaHSO3 concentrations was studied by electrochemical measurements, periodic wet/dry cyclic corrosion test, atomic force microscopy and surface morphology analysis. The results show that with the addition of HSO3-, the passivation state presented by the anode branch evolves into an activated state, and the alloy corrosion is facilitated, as well as the corrosion form changes from slight pitting corrosion to exfoliation corrosion. The corrosion resistance is correlated to the state of the film generated on the surface of 6061 alloy. In addition, at the concentration of 0.05 M HSO3-, there is a tendency for the corrosion to be retarded. HSO3- promotes micro-galvanic corrosion between the alloy matrix and the precipitated phase of AlFeSi, resulting in the occurrence of dense pits and the dissolution of AlFeSi phase.