Anodic polarization behaviour of sputter-deposited AlZr alloys in a neutral chloride-containing buffer solution

Abstract

Sputter-deposited AlZr alloys consist of a single α-Al phase supersaturated with zirconium at the alloy zirconium content of 11 at.% or less, and become amorphous at higher zirconium contents. The sputter-deposited alloys possess better passivating ability and pitting corrosion resistance in a deaerated borate—boric acid solution containing Cl − ions at pH 8.4 and 25°C than do argon arc-melted counterparts. The pitting potentials of the sputter-deposited alloys continuously increase with the alloy zirconium content, and are significantly higher than those of argon arc-melted counterparts. XPS analysis reveals that the surface film consists of a solid solution oxide of Al 3+ and Zr 4+ ions containing a small amount of OH –. The ennoblement of the polarization potential in the passive region results in increases in the film thickness and the cationic fraction of zirconium. The cationic fraction of zirconium is almost the same as or slightly higher than the alloy composition. The surface films forms on these alloys are not composed of a simple mixture of aluminium oxide and zirconium oxide but consist of a solid solution, such as (Al 3+ a Zr 4+ 1- a )O 2– b (OH) − 4- a-2 b .