Process for electrolytically pickling chromium-containing stainless steel
US4851092A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 3, 1988 |
| Grant date | Jul 25, 1989 |
| Priority date | — |
| Expiry date | May 3, 2008 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC25F1/06
- WIPO fieldSurface technology, coating
- WIPO sectorChemistry
Abstract
In a process for the electrolytic pickling of chromium-containing stainless steel, pickling proceeds initially in an aqueous Na.sub.2 SO.sub.4 solution and subsequently in acid, preferably mixed acid. The CrO.sub.4.sup.2- formed is converted by the addition of reducing agent and acid as a function of the pH value and the redox potential to Cr.sub.2 (SO.sub.3).sub.3 or Cr.sub.2 (SO.sub.4).sub.3. H.sub.2 SO.sub.4 serves as the acid and a substance is used as a reducing agent selected from the group Na.sub.x H.sub.y S.sub.z O.sub.v, wherein x=0 to 2, y=0 to 2, y=1 to 6 and v=2 to 6. The pH value is adjusted to less than three by the addition of acid.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.