Fabrication of electrically conductive metal oxide coatings by reactive ion plating

Abstract

Electrically conductive metal oxide (ceramic) coatings produced by reactive ion plating are being investigated at USA-CERL for potential application in cathodic protection systems. Ceramic materials are advantageous because of their very low dissolution rates (typically less than 1 g/A/yr in 3.5% NaCl solution) and ease of fabrication. Among the ceramic anode materials currently under investigation are two systems: (1) a mixture of titanium oxide and ruthenium oxide and (2) a mixture of titanium oxides ‘‘doped’’ with niobium, each ion plated on niobium substrates. The mixed oxide coatings were fabricated by a reactive ion plating process involving oxygen and dual electron beam evaporation sources. An enhanced plasma was used to increase reactivity. X-ray diffraction, scanning electron microscopy, and energy dispersive x-ray spectroscopy have been used for characterization of the microstructure, crystallography, and elemental composition of the coating.