A novel low-VOC, chromate free, one-step primer system for corrosion protection of metals and alloys
Abstract-Corrosion of aerospace metals and alloys is currently mitigated using a two-step chromatebased technology. Cr(VI), however, has been identified as carcinogenic and toxic by the US Environmental Protection Agency. Also, the volatile organic compound (VOC) content of primers used in the coating industry is coming under strict regulation by the various occupational safety and environmental agencies. The paint industry seeks a low-VOC, chromate-free alternate to replace the existing two-step chromate-based system. We report here on a series of one-step organic primers obtained by combining resins such as epoxies, acrylates and polyurethanes with organofunctional silanes. These primers are low in VOC and chromate-free. In this paper, we present some formulations which have been successfully tested for corrosion protection performance using standard tests, such as ASTM B117 salt-spray test, electrochemical impedance spectroscopy, DI water contact-angle measurements, ASTM D 3363 (pencil hardness test), ASTM D 4752 (MEK double rub test) and ASTM D 3359 (topcoat adhesion test). The results of these performance tests on our novel primer systems are reported in this paper.