Two-step electrochemical process for coating magnesium alloys
US5264113A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 15, 1991 |
| Grant date | Nov 23, 1993 |
| Priority date | — |
| Expiry date | Jul 15, 2011 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC25D11/30
- WIPO fieldSurface technology, coating
- WIPO sectorChemistry
Abstract
A two-step process for the coating of magnesium and its alloys is disclosed. The first step comprises immersing the magnesium workpiece in a first electrochemical solution comprising about 3 to 10 wt-% of a hydroxide and about 5 to 30 wt-% of a fluoride having a pH of at least about 12. By controlling a current density to about 10 to 200 mA/cm.sup.2, an increasing voltage differential is established between an anode comprising the pretreated article and a cathode also in contact with the electrolytic solution. Next, the article is immersed in an aqueous electrolytic solution having a pH of at least about 11 and which solution is prepared from components comprising a water soluble hydroxide, a water soluble fluoride source and a water soluble silicate in amounts to result in an addition of about 2 to 15 g of a hydroxide per liter of solution, about 2 to 14 g of a fluoride per liter of solution and about 5 to 40 g of a silicate per liter of solution. Again, by controlling the current density to about 5 to 100 mA/cm.sup.2, an increasing voltage differential of at least about 150 volts is established between an anode comprising the pretreated article and a cathode also in contact with …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.