Effect of alternating voltage on the pitting of aluminum in nitrate, sulfate, and chloride solutions

Abstract

A study has been made of the effect of 60-Hz sinusoidal, square, and triangular alternating voltages (AV) on the corrosion of aluminum in dilute nitric acid, sodium nitrate, sodium sulfate, and sodium chloride solutions. The anodic polarization curves and the pitting behavior of aluminum were examined with an AV modulation technique over a range of AV magnitudes from 0 to 2000 mV rms. The results revealed that AV reduced the passive potential regime of aluminum by shifting the passive-transpassive transition potential toward the negative direction and the active-passive transition potential toward the positive direction. AV destroyed the passivity of aluminum in the nitrate solutions and caused the pitting corrosion to occur at more negative DC potentials. Additional study results are discussed.