The effect of molybdenum ion implantation on the general and pitting corrosion behaviour of pure aluminium and a high strength aluminium alloy

The effect of Ar and Mo ion implantation on the corrosion behaviour of pure Al and a high strength aluminium alloy (7075-T6) has been investigated in Cl^?-free and Cl^?-containing sulphate solutions. In Cl^?-free environments, Mo implantation markedly affects the general corrosion behaviour of both the pure metal and the alloy. Ar implantation, on the other hand, has no permanent effect on the potentiodynamic polarization behaviour of pure Al but does alter somewhat the polarization characteristics of 7075-T6. In Cl^?-containing environments, Mo implantation significantly improves the resistance of pure Al to pitting corrosion, and increases the breakdown potential by about 200 mV. A similar, though less marked effect is observed with the alloy. Ar implantation has no major effect on the behaviour of either the pure metal or 7075-T6 in Cl^?-containing environments. On the basis of Rutherford backscattering and potential-time measurements it is suggested that the beneficial effect of Mo may be due to either the incorporation of Mo in the passive film or to dissolution and reprecipitation of some Mo-containing species on the passive film.