Toward an understanding of overcoat corrosion protection

This paper presents detailed electrochemical investigations on the role of overcoat and lubricant in head and media corrosion protection. Depending on the types of metal to be protected, some types of overcoat materials can actually accelerate corrosion due to galvanic coupling effect. To eliminate such coupling, a true dielectric film needs to be used instead of the conventional hydrogenated carbon films. On the other hand, galvanic coupling is not always detrimental depending on the types of materials to be protected.