Current metal primers utilized by the US Air Force contain chromates to inhibit corrosion of the underlying metal. These chromates are both highly toxic and carcinogenic and pose a severe health risk to personnel involved in their application, stripping and disposal. Environmentally-friendly primers with Chromate replacements have historically performed poorly with respect to corrosion inhibition. The purpose of this study was to investigate the interaction of chromates with microorganisms in an environment not traditionally associated with biologically-enhanced corrosion to determine if corrosion inhibition by a Chromate pigment is, in part, through its action as a biocide. Inoculation of panels which had been coated with a nonchromated primer prior to salt fog exposure and storage in humid conditions resulted in a significant growth of filiform corrosion around a scribe mark. The presence of Chromate in the primer severely limited the formation of this corrosion. Likewise, in the absence of the inoculation procedure, the extent of corrosion was strongly diminished. These results suggest that the Chromate may be acting as a biocide to limit corrosion which is enhanced by the presence of biological activity.
- Microbially-induced corrosion