Electrolytic formation of chromite coatings
US4169022A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 22, 1978 |
| Grant date | Sep 25, 1979 |
| Priority date | — |
| Expiry date | May 22, 1998 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC25D11/38
- WIPO fieldSurface technology, coating
- WIPO sectorChemistry
Abstract
A method of depositing a protective chromite conversion coating is described. The chromite coatings produced by the method contain no Cr.sup.VI. The electrolyte used in the method comprises Cr.sup.III ions in a concentration of not more than 1 molar and a weak complexing agent for Cr.sup.III ions. The electrolyte, preferably, also contains conductivity salts. The method involves using a cathode current density of not more than 2000 amps per square meter and a temperature of not more than 35.degree. C. for a period of not more than 3 minutes. The chromite conversion coatings can be improved by aging and can be subsequently painted or lacquered. The Cr.sup.III electrolytes used are much less corrosive than Cr.sup.VI electrolytes and thus the substrates which can be coated include materials which cannot readily be chromate coated because they are reactive towards Cr.sup.VI electrolytes.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.