Electrochemical behaviour of Al alloys in aerated and deaerated NaCl solution

The electrochemical corrosion behaviour of wrought AI alloys 2011-T8, 6061-T4, and 6061-T6 was studied in aerated and deaerated 3.5wt% NaCl solution at 23°C and compared with that of aluminium. The microstructural examination was performed by light and scanning-electron microscopy, while open-circuit potentials (OCP), corrosion rates, and pitting potentials of the alloys were determined using potentiodynamic and cyclic polarization techniques. The OCP values for all the alloys increased towards the negative in the deaerated compared to aerated solutions. The OCP values in the aerated solutions were generally stable within a 100mV range. The corrosion rates in the aerated solutions were higher than those in the deaerated solutions. All alloys exhibited a degree of susceptibility to pitting attack, with the pitting potentials coinciding roughly with the OCP values in the aerated solutions. The alloys 6061-T4 and 6061-T6 exhibited protection potentials (E_prot) in the deaerated solutions.