Zinc Phosphate

Zinc Phosphate

Zinc Phosphate is a white, corrosion inhibiting pigment used in protective coatings. It is also used as an additive in electroplating processes. Zinc phosphate is nonrefractive and has a narrow particle size distribution with an average diameter of 5 microns. It is compatible with a variety of resin systems including high acid value, catalyzed, and vinyls. It is compliant with ASTM D 6280-98 Specifi cation for Corrosion Inhibiting Pigment Type I.

Zinc phosphate is a conversion coating that is applied to metal substrates before painting or other surface treatment. It prevents metal-to-metal chemical reactions, enhances paint adhesion, increases lubrication for cold-forging and wire drawing, and protects the surface from galling between threaded or geared surfaces.

The zinc phosphide compound is toxic to humans when ingested because it rapidly converts to phosphine gas in the stomach. The toxicity of phosphine gas is similar to that of arsenic.

A hazard assessment of zinc phosphide was performed by the U.S. Environmental Protection Agency, or EPA, in 1998 and found to be not hazardous under the conditions of use. The hazard assessment included an acute and chronic assessment of both the physical and ecological effects of exposure to zinc phosphide.

A 90-day subchronic study was conducted with rats, and a NOEL of 0.1 mg/kg/day was established. Male rats exposed to zinc phosphide at the 1.0 and 3.0 mg/kg/day dose levels developed kidney infections and excess salivation. The hazard assessment concluded that chronic exposure to zinc phosphide is not expected to cause cancer in humans, but it may cause a variety of adverse health effects in other species including reproductive and developmental problems, nausea and vomiting, irritation of the respiratory tract, skin burns, and eye and throat damage. See the text box on Carcinogens for further information. The hazard assessment of the zinc phosphide analogue, sodium pyrophosphate, is available in the EPA’s Toxicological Profile for Zinc Phosphate.

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