The corrosion behavior of sputter-deposited amorphous copper-tantalum alloys in 12 M HCl

Abstract

Cu-Ta alloys containing 447ndash;91 at% tantalum are amorphous and are spontaneously passive showing almost the same low corrosion rate as that of tantalum metal. Formation of a single fcc Cu phase alloy supersaturated with tantalum of up to 21 at% of tantalum is not effective in enhancing the corrosion resistance in aggressive 12 M HCl. The passive films on the amorphous alloys and tantalum metal consist only of Ta 2O 5. The passive films on Cu-28Ta and Cu-36Ta alloys consisting of a mixture of microcrystalline fcc Cu phases in the amorphous matrix are composed of TaO 2OH and are thicker and less protective in comparison with the Ta 2O 5 film. Polarization at potentials higher than potentials for oxygen and chlorine evolution prevents the formation of the tantalum-enriched passive film on the amorphous Cu-Ta alloys and results in sharp increase in the anodic current.