| 摘要 |
<p>1377772 Electro-depositing chromium DIAMOND SHAMROCK CORP 18 Feb 1972 [19 Feb 1971] 7597/72 Heading C7B An aqueous bright chromium plating bath com- prises (A) a complex water-soluble trivalent chromium compound containing non-aromatic carboxylic acid constituent of less than 10 C atoms, e.g. glycolic, lactic and/or oxalic acid; and (B) an organic component (up to 5 vol per cent) selected from (1) the polar aprotic substances tetrahydrothiophene-1,1-dioxide, dimethyl-sulphoxide,-sulphone or-formamide and/or N-methylpyrrolidone, or ring-substituted derivatives of such substances having alkyl, alkoxy, hydroxyalkyl and/or dialkylamine substituents on less than 4 ring C atoms; and (2) cyclic or acyclic ethers or thioethers having an atomic ratio of O and/or S to C of between 0.25 and 0.9:1. Component (2) may be bis (2- methoxyethyl)ether, dipropylene glycol, tetraethylene glycol, butoxytriglycol, diethylene glycol monomethyl ether, 1-(2-methoxypropoxy)-2- propanol, vinyl sulphide, tetrahydrofuran and/or tetrahydrofurfuryl alcohol. The chromium compound containing the carboxylic acid and preferably also halogen constituents may be prepared as described in Specification 1376022. The bath may also contain 50-200 g/l Na and/or K chloride or perchlorate to enhance conductivity and 10-70 g/l boric acid or borax, boron oxide and/or sodium oxyfluoborate. Alkali metal carbonate or hydroxide may be added to adjust pH within range 1.8 to 4.9. An anode of graphite, Pt or platinized Ti may be used. The substrate may be of steel, brass, bronze, Cu (alloy), a Zn die casting or Ni.</p> |
