| 摘要 |
In a method of electrolytically descaling a ferrous material such as Ni or Ni-Cr steel using a solution as described in Specification 1,082,409, the soluble fluoride being optional, the metals dissolved during electrolysis are recovered, e.g. by adjusting the pH of the solution to 3 to 5 by adding sulphuric, hydrofluoric and/or nitric acid to precipitate iron hydroxide, removing the iron hydroxide, then raising the pH to precipitate additional metal ions as their hydroxides and removing these hydroxides; e.g. chromium hydroxide may be precipitated at a pH of 5 to 6 and nickel hydroxide at a pH of 6 to 8, the pH being adjusted by adding alkali metal hydroxide (NaOH and/or KOH). After removal of hydroxides, the solution may be recycled for use as electrolyte in further descaling, the pH being adjusted to 6 or 7.
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