Claims
- 1. A method of electrocating a tin or tin plated article with a non-hexavalent trivalent chromium oxide and/or trivalent chromium hydroxide protective coating comprising:
- cleaning the tin or tin plated article,
- making the cleaned article a cathode of an electrolytic cell having a dilute sodium carbonate solution to provide a clean reactive surface tin or tin plated article,
- rinsing the clean reactive surface tin or tin plated article,
- placing the rinsed clean reactive surface tin or tin plated article as a cathode in an electrolytic trivalent chromium electrolyte which is a trivalent chromium composition free of chromium complexing agents and said trivalent chromium composition having a pH of about 2.25 to about 2.40 and comprises a trivalent chromium compound selected from the group consisting of potassium chromium sulfate, chromium sulfate chromium chloride and hydrates thereof; and
- applying electrical current to the cathode for about 2 to 10 seconds to provide a trivalent chromium oxide and/or hydroxide protective coated tin or tin plated article.
- 2. A method for electrocoating a tin or tin plated article with a non-hexavalent trivalent chromium oxide and/or trivalent chromium hydroxide protective coating comprising:
- cleaning the tin or tin plated article to provide a clean tin or tin plated article,
- placing said clean tin or tin plated article as a cathode in an electrolytic trivalent chromium electrolyte which is a trivalent chromium composition free of chromium complexing agents and having a pH of about 2.0 to about 3.0; and
- applying electrical current to the cathode to provide a trivalent chromium oxide and/or
- hydroxide protective coated tin or tin plated article.
- 3. The method of claim 2 wherein the pH range is about 2.25 to about 2.40.
- 4. The method of claim 3 wherein said trivalent chromium composition comprises trivalent chromium compounds selected from the group consisting of potassium chromium sulfate, trivalent chromium chloride, trivalent chromium sulfate and the hydrates thereof.
- 5. The method of claim wherein the article is exposed to the trivalent chromium composition for up to 30 seconds.
- 6. The method of claim 5 wherein the tin or tin plated article is exposed to the trivalent chromium composition for about 2 to 5 seconds.
- 7. The method of claim 2 wherein the pH is about 2.0 to about 2.4; and
- applying electrical current to the cathode for up to 30 seconds to provide said trivalent
- chromium oxide and/or hydroxide protective coated tin or tin plated article.
- 8. The process claimed in claim 7 wherein the concentration of chromium (III) is maintained above 0.05 grams per liter of solution.
- 9. The process as claimed in claim 8 wherein said chromium (III) is a chromium salt selected from the group consisting of potassium chromium sulfate, a chromium sulfate, a chromium chloride, and hydrates thereof.
Parent Case Info
This application claims the benefit of International Application PCT/US96/13859, with an International filing date of Aug. 20, 1996. This application is also a continuation of U.S. patent application Ser. No. 08/521,832 filed Aug. 31, 1995, still pending.
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
102e Date |
371c Date |
PCT/US96/13859 |
8/30/1996 |
|
|
2/24/1998 |
2/24/1998 |
Publishing Document |
Publishing Date |
Country |
Kind |
WO97/08364 |
3/6/1997 |
|
|
US Referenced Citations (21)
Non-Patent Literature Citations (1)
Entry |
Process technology for the production of highly passivated tinplate by Jargon, F.; Maschke, E. 1975. No month available. |