Trivalent chromate conversion coating
AssigneePavco, Inc.
InventorsLeonard L. Diaddario, JR., Michael Marzano
Life of this patent
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Abstract
In a preferred embodiment of the present invention, a conversion coating composition comprising chromium (III) ions, cobalt (II) ions, and nitric acid is provided. The coating composition is substantially free of chromium (VI) ions and substantially free of an oxidizing agent. The present trivalent chromium based conversion coating provides corrosion protection equal to or greater than most hexavalent chromium conversion coatings.
Claims24
A conversion coating bath including a coating composition comprising:
- a. chromium (III) ions,
- b. cobalt (II) ions, and
- c. nitrate ions,
- said composition including a ratio of nitrate ions to the combination of chromium (III) and cobalt (II) ions of less than 1.5:1 being substantially free of chromium (VI) ions and substantially free of an oxidizing agent.
A conversion coating bath composition comprising:
- a. about 0.020 to 0.075 mole/L chromium (III) ions,
- b. about 0.010 to 0.035 mole/L cobalt (II) ions,
- c. a film polishing agent, and
- d. about 0.010 to 0.045 mole/L nitrate ions,
- said composition being substantially free of chromium (VI) ions and substantially free of an oxidizing agent.
A concentrate for forming a conversion coating bath comprising:
- a. chromium (III),
- b. cobalt (II), and
- c. nitric acid,
- and being substantially free of chromium (VI) ions and substantially free of an oxidizing agent and including less than 1.5 to 1 nitric acid to chromium (III) plus cobalt (II).
A method for applying a conversion coating onto an article comprising the steps of:
- a. plating the article with zinc, and
- b. exposing the article to a conversion coating composition comprising water, chromium(III) ions, cobalt(II) ions, fluoride ions, and nitrate ions, said conversion coating being substantially free of chromium (VI) ions and substantially free of an oxidizing agent, and including a ratio of nitrate ions to chromium (III) and cobalt (II) ions of less than 1.5:1.
A method for applying a colored conversion coating onto an article comprising the steps of:
- a. plating the article with zinc,
- b. exposing the article to a conversion coating composition comprising water, chromium(III) ions, cobalt(II) ions, fluoride ions, and nitrate ions, said conversion coating being substantially free of chromium (VI) ions and substantially free of an oxidizing agent,
- c. rinsing the article,
- d. exposing the article to a dye solution, and
- e. rinsing the article.
Dependencies are inferred from the claim text.