Adhesion, Ductility, and Fracture of Anodic Oxide Films on Tantalum

Abstract

Spectrophotometric thickness measurements have confirmed that anodic oxide films on tantalum can show considerable plastic flow when the oxide‐coated metal is stretched or rolled, for example up to 15% reduction in the average thickness of oxide. SEM pictures showed that after a certain amount of deformation the oxide cracks and widening areas of "bare" metal develop. The ductile behavior is seen if chemically polished tantalum is etched in or treated with boiling water before anodization. Otherwise the fluoride in the film left by chemical polishing modifies the oxidation process in a way which leads to a poorly adherent anodic oxide film.