Point defect model and corrosion of anodic oxide coatings on Ti–6Al–4V

Electrodeposited anodic oxide coatings were produced on Ti–6Al–4V substrates using (i) phosphoric acid and (ii) aqueous electrolyte containing dissolved calcium and phosphorus. Different coatings were produced by varying the time periods. The coatings contained lower oxides of titanium and small quantities of phosphorus and/or calcium deposited from the electrolyte. Coatings produced from shorter duration had higher resistance to corrosion by simulated body fluid. Point defect model is obeyed by all the coatings. As postulated by this model, coatings containing calcium are attacked more by simulated body fluid than coatings which do not contain calcium.