Corrosion of thin film cobalt based magnetic recording media

Corrosion resistance of cobalt based magnetic recording media with and without carbon overcoats was investigated. Wet oxidation of unprotected alloys led to the preferential formation of cobalt oxide and hydroxide. Cobalt migration through carbon was discovered at ambient conditions and elevated temperature and humidity. This corrosion process is electrochemical, involving cobalt dissolution in adsorbed water, migration of cobalt ions through permeable carbon and precipitation of cobalt rich particles on the carbon surface.