THE EFFECT OF MAGNESIUM ON THE CORROSION BEHAVIOR OF SPUTTER-DEPOSITED AMORPHOUS AL-MG-TI TERNARY ALLOYS IN A NEUTRAL CHLORIDE SOLUTION

Magnesium additions have been made to enhance the passivity of Al-Ti alloys prepared by sputter deposition. The corrosion behavior of amorphous Al-Mg-Ti alloys in a neutral borate-boric acid solution with chloride ions has been investigated by electrochemical measurements. Particular attention is paid to the effect of magnesium on the corrosion behavior and surface film composition. Alloys containing relatively low concentrations of titanium and low concentrations of magnesium possess a better resistance against pitting corrosion in comparison with the Al-Ti binary alloys with the same titanium contents, because an increase in alloy reactivity by the magnesium addition leads to preferential dissolution of not only magnesium but also aluminum with a consequent enrichment of titanium cations in the surface film. The addition of excessive amounts of magnesium lowers the pitting potential and increases the passive current density due to a decrease in the stability of the passive film and due to an excessive increase in alloy reactivity.