摘要 |
A heat curable protective coating composition for providing barrier protection to a solid substrate. The coating composition comprises an aqueous solution of phosphate ions and nitrate ions and at least one species of metal ion having a valency greater than +1. The metal ions may be selected from the group consisting of aluminum ions, manganese ions, magnesium ions, cerium ions, cobalt ions, chromium(III) ions, nickel ions, iron ions, copper ions, and zinc ions. The composition has a pH in the range from about 0.5 to about 3.5. The composition is substantially free of chromate ions and molybdate ions. A cured topcoat is substantially clear and has a glossy appearance.
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