This Small Business Innovation Research Phase I project will demonstrate the feasibility of using a new approach to apply molybdate (hexavalent molybdenum) conversion coatings to aluminum alloys and anodized aluminum for aircraft applications. Chemical conversion coatings, particularly chromate conversion coatings, have found widespread commercial and military applications. Of particular interest is the use of chemical conversion coatings on aircraft aluminum alloys, because of their excellent corrosion resistance and their ability to serve as an effective base for paint. Conventional baths used to develop this coating contain chromates (hexavalent chromium), and it is the residual chromates in the coating that are largely responsible for the high degree of corrosion inhibition observed. However, chromates are highly toxic and their presence in wastewater effluents is severely restricted. Thus, it is highly desirable to develop a coating for aluminum alloys and anodized aluminum utilizing non-toxic chemicals that could serve as an alternative to the conventional chromate coating process. The key to the proposed project is the use of `Advanced Oxidation Processes (AOPs)` to promote the oxidation of low valence molybdenum to hexavalent molybdenum in a post-treatment stage and, hence, enhance the formation of protective oxide films on aluminum alloys. The proposed procedure is simple, environmentally benign, and can be applied by brushing or spraying. This project should produce a viable alternative to the polluting conventional chromate conversion process used for a multitude of commercial and military end items. The molybdate (hexavalent molybdenum) process could eventually replace conventional chromate conversion coatings for commercial applications. Developed technology will also be beneficial with respect to the environment and human health.
