THE PITTING CORROSION BEHAVIOR OF SPUTTER-DEPOSITED AMORPHOUS AL-TI ALLOYS IN A NEUTRAL CHLORIDE-CONTAINING SOLUTION

Pitting corrosion behavior of sputter-deposited amorphous AlTi alloys in a neutral borate-boric acid solution with Cl- ions has been compared with that of argon arc-melted crystalline counterparts. The sputter-deposited amorphous AlTi alloys possess a better passivating ability and pitting corrosion resistance. They exhibit lower passive current densities and pitting potentials which are about 500 mV higher than their crystalline counterparts. Crystallization of the amorphous alloys by heat treatment leads to a decrease in the pitting potential. Pits formed on the amorphous AlTi alloys are featureless smooth holes, and those on the argon arc-melted alloys show facetting dissolution. The pit bottom of the argon arc-melted Al-36Ti alloy is enriched with titanium; thus pitting corrosion involves preferential dissolution of aluminum. Sputter-deposited alloys containing ≤ 30 at.% titanium consist of a single fcc α-Al phase supersaturated with titanium, and their pitting potential is raised with increasing titanium content. © 1990.