Study of Al alloy corrosion in neutral NaCl by the pitting scan technique

The corrosion behavior of commercial Al alloys was studied in neutral 0.6 mol L⁻¹ NaCl by using single-cycle polarization. Qualitative interpretation of pitting scans in both deaerated and naturally aerated NaCl solution, with the aid of corrosion morphology characterization, allowed for inference of the features of localized corrosion as a function of Al substrate nature. Electrochemical characteristic parameters such as pitting (E_pit), repassivation or protection (E_prot) potentials and pit transition potential (E_ptp) were determined. The validity of the difference ΔE = |E_pit − E_prot| as criterion for susceptibility to localized corrosion of aluminium alloys is discussed.