Effect of Nitrate on Pitting Corrosion of Aluminum Alloy

The influence of nitrate on the pit nucleation and growth on aluminum alloy in sodium chlorine solution was investigated by potentiodynamic techniques. At low concentration, nitrate changed the potential from passive to active region. But, it shifted the repassivation potential towards positive direction. When aluminum alloy was being passive, nitrate could repair the passive film of aluminum. At higher concentration, nitrate shifted the pitting and repassivation potential towards positive direction, which indicated the suppression of pit nucleation and propagation. The big or small of concentration has a bearing on concentration of chlorion.