| 摘要 |
A technique for improving the tarnish and oxidation resistance of metallic substrate is disclosed. The substrate is immersed in an aqueous solution containing sodium hydroxide, zinc ions and chromium (VI) ions. Either the temperature of the aqueous solution or the current density is selected so that at least one surface of the substrate is coated with a nontransparent layer. A chromium-zinc coating is electrolytically applied. The coating provides tarnish resistance at temperatures in excess of 230 DEG C. The coating is removable by immersion in sulfuric acid. Improved results are obtained by rinsing deionized water containing a small amount of an alkaline or alkaline earth hydroxide.
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