Chromate Dissociation from Three Types of Paint Particles

Chromate-containing primer paints are used to inhibit corrosion on metal surfaces. Though chromate contains hexavalent chromium (Cr6+), a human carcinogen, there is little epidemiological evidence of increased lung cancer among spray painters. One reason may be that the paint matrix hinders the release of Cr6+ from the paint particle during the time that the particle is within the lungs. This study measures the mass of Cr6+ released from particles originating from three types of paint particles: solvent-borne epoxy, water-borne epoxy, and polyurethane. Impingers were used to collect paint particles into water and particles were held in the water at rest for 1 and 24 h residence times. Particles were then separated from the water by centrifugation. The supernatant was tested for dissolved Cr6+, which was compared to the total Cr6+ (dissolved Cr6+ plus Cr6+ in particles). The mean fractions of Cr6+ released into the water after 1 and 24 hours for each primer averaged: 70 and 85 (solvent epoxy), 74 and 84% (water epoxy), and 94 and 95% (polyurethane). Correlations between particle size and the fraction of Cr6+ released indicate that smaller particles (<5 μm) release a larger fraction of Cr6+ versus larger particles (>5 μm).