Isomolybdate conversion coatings
US6432224B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Feb 8, 2000 |
| Grant date | Aug 13, 2002 |
| Priority date | — |
| Expiry date | Feb 8, 2020 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC23C22/68
- WIPO fieldSurface technology, coating
- WIPO sectorChemistry
Abstract
A conversion coating solution and process forms a stable and corrosion-resistant layer on metal substrates or layers or, more preferably, on a boehmite layer or other base conversion coating. The conversion coating process involves contacting the substrate, layer or coating with an aqueous alkali metal isomolybdate solution in order to convert the surface of the substrate, layer or coating to a stable conversion coating. The aqueous alkali metal molybdates are selected from sodium molybdate (Na2MoO4), lithium molybdate (Li2MoO4), potassium molybdate (K2MoO4), or combinations thereof, with the most preferred alkali metal molybdate being sodium molybdate. The concentration of alkali metal molybdates in the solution is preferably less than 5% by weight. In addition to the alkali metal molybdates, the conversion coating solution may include alkaline metal passivators selected from lithium nitrate (LiNO3), sodium nitrate (NaNO3), ammonia nitrate (NH4NO3), and combinations thereof; lithium chloride, potassium hexafluorozirconate (K2ZrF6) or potassium hexafluorotitanate (K2TiF6).
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.