Metallic-Ceramic Coatings as Replacements for Cadmium Plating

Cadmium plating has been used as a corrosion resistant coating for aerospace components for many years. Cadmium plating provides good corrosion resistance with excellent self lubricating properties. In spite of these properties, continuing efforts are underway worldwide to eliminate cadmium because of environmental concerns. Alternative processes are being investigated.

Metallic - ceramic coatings which contain active aluminum metal powder as pigment have been proposed as cadmium replacements. These coatings have been in use for many years in air frame applications where cadmium plating could not be used because of part size, temperature exposure extremes, or part configuration. Examples of such components are described.

Recently devised dense pack metallic-ceramic coatings show improved performance in which lower cure temperatures are possible and corrosion resistance is significantly upgraded when compared to original formulations. Laboratory tests are described in which these coatings are exposed to a variety of environmental tests and cyclic heat exposure. Results of physical testing are also summarized. Test results showing compatibility with various topcoats, including epoxy polyamide primers and urethane paint systems are included. Results are summarized. Examples of hardware specifying these new coatings are described.