Correlation of the open‐circuit and electrochemical measurements for the pitting corrosion of aluminim in chloride media

Abstract Pitting of aluminium in NaCl solutions has been investigated by open‐circuit and polarization studies in 3% NaCl solutions. The variation of the corrosion potential has been measured with respect to time for various Al alloys; however, the emphasis has been on the commercially‐poure 1 S (Al 99,5) and the super‐pure metal. In addition, polarization data have been obtained for the 1S alloy under potentiostatic and galvanostatic conditions in deaerated solutions. The results indicate that pit initiation, propagation, and repassivation show certain reproducible trends as a function of potential and time. Pits initiate only above a critical pitting potential and repassivate below a more active protection potential in support of the classical theories. Pit propagation occurs on a macroscopic front or exhibits intercrystalline nature depending on whether the potential is, respectively, above or below the pitting potential. Open‐circuit and polarization data are in full correspondence regarding all phase of aluminium corrosion.