Effect of chloride concentration on the repassivation behavior of structural Al alloys

The present work reports on the effect of chloride concentration on the repassivation behavior of commercial aluminum alloys Al 5754-H111, Al 5083-H111, Al 2024-T3 and Al 7075-T6. Characteristic parameters of pitting and repassivation processes were determined from single cycle anodic polarization curves recorded in different NaCl solutions. Empirical relationships of the characteristic parameters as a function of log [Cl-] were derived from repeated experiments. Data analysis was complemented by corrosion morphology examination. Overall results show that valuable information on the corrosion resistance of different Al alloys can be obtained from the polarization response during the reverse scan. In the presence of localized attack other than pitting, the passivation of active surfaces follows a more complex mechanism.