METAL PRETREATMENT COMPOSITION CONTAINING ZIRCONIUM, COPPER, ZINC, AND NITRATE AND RELATED COATINGS ON METAL SUBSTRATES

摘要

Disclosed is a pretreatment composition for a metal that provides enhanced corrosion resistance, enhanced paint adhesion and reduced chip damage. The pretreatment is also cleaner because it is based on zirconium rather that zinc phosphates. The pretreatment coating composition in use preferably comprises 50 to 300 parts per million (ppm) zirconium, 0 to 100 ppm of SiO2, 150-2000 ppm of total fluorine and 10- 100 ppm of free fluorine, 150 to 10000 ppm of zinc and 10 to 10000 ppm of an oxidizing agent and has a pH of 3.0 to 5.0, preferably about 4.0. The coating composition can optionally include 0 to 50 ppm of copper. The suitable oxidizing agents can be selected from a large group. The pretreatment coating composition greatly enhances the corrosion resistance of a wide variety of metal substrates including cold rolled steel, hot rolled steel, stainless steel, steel coated with zinc metal, zinc alloys such as electrogalvanize steel, galvalume, galvanneal, hot dipped galvanized steel, aluminum alloys and aluminum substrates.