Alternative Coating Sealing Process for Passivating Al Mg Substrates
Original Publication Date: 1981-Apr-01
Included in the Prior Art Database: 2005-Feb-11
The stability of thin film magnetic disks in corrosive environments is of considerable interest. Usually, such a disk consists of a multilayer coating on an Al-Mg substrate. The outer layer is a hard protective metal, such as Rh, which is applied over a thin film of magnetic material. Beneath these layers is a several mu m thick Haynes metal layer which is polished to produce a smooth surface and simultaneously provide a barrier layer between the atmosphere and the Al-Mg substrate. In tests, such a structure has not withstood the corrosive ambient. This is believed to be due to the presence of defects in the various layers which permit the ambient to come in direct contact with the substrate. Galvanic corrosion occurs, and the resulting products cause blisters to form.