| 摘要 |
1,188,591. Electrolytic chromate coating of chromium plated steel. FUJI IRON & STEEL CO. Ltd. March 28, 1967 [March 28, 1966; March 15, 1967], No. 14085/67. Heading C7B. Chromium plated steel is subjected to cathodic treatment in an aqueous solution containing per litre 5 to 300g. chromic anhydride and one or more hydroxides and/or carbonates of lithium, sodium, potassium, magnesium, calcium and/or strontium until an almost colourless and transparent corrosion-resistant chromate coating is formed on the chromium plate, the solution containing by weight relative to the CrO 3 content at least 20% of said hydroxides and/or carbonates when the CrO 3 , concentration is 20 to 60 g/1 and at least 10% of said hydroxides and/or carbonates when the CrO 3 concentration is 5 to 20 or 60 to 300 g/1. Preferably the solution also includes as deposition accelerators one or more of soluble halogencontaining compounds, e.g. NaCl, HClO 3 , NaClO 3 , Na 2 SiF 6 , (NH 4 ) 2 , TiF 6 , CrCl 3 ; salts such as NaNO 3 , Na 2 SO 4 , SnSO 4 , Cr 2 (SO 4 ) 3 ; aromatic hydroxy sulphonic acids e.g. phenol mono- or di-sulphonic acids; or soluble salts of metalcontaining anions e.g. Na 2 SnO 3 , NaAlO 2 . The trivalent chromium content of the bath may be up to 10 g/1. Typically the chromating is effected at a temperature between room temperature and 90‹ C. employing a current density of 1 to 45 amps/dm<SP>2</SP> for a period of 0À1 to 15 seconds. The chromium plating thickness may be from 0À001 to 0À1Á. The chromate coating maybe completely obscured by a thin paint coating e.g. 15 Á of white alkyd paint. Specification 1,187,785 is referred to. |
