DEVELOPMENT OF IMPROVED THERMALLY CONDUCTIVE COATINGS FOR ALUMINUM HARDWARE

Many shipboard systems and components are fabricated from aluminum alloys because of the high strength to weight ratio, relatively low cost, and ease of manufacturing associated with such materials. Disadvantages in the use of these materials are encountered when a marine service environment is involved - particulary when the aluminum component is in direct contact with a dissimilar metal and large galvanic currents cause severe corrosion. Hard anodizing has been beneficial in detering corrosion but it has poor thermal conductivity. Thick electroless nickel has met with significant success as a corrosion deterrent and has good abrasion and wear resistance. It has much poorer thermal conductivity than most electrodeposited metal coatings and suffers poor ductility when impacted. This proposal offers a unique program for fabrication of families of protective coatings on aluminum alloys where outstanding thermal conductivity can be obtained while providing excellent adhesion to the substrate and ability to conform to damages by surface impact - still retaining good corrosion protection and wear resistance. The process is based on the dilute phosphoric acid anodizing process which provides a very thin galvanic insulator to deter corrosion while forming a bonding media for metallic coatings having properties being sought.