| 摘要 |
Bright Cd is electroplated from a bath containing a Cd complex alkali metal cyanide and an oxidized water-soluble polyvinyl alcohol as a brightener. Auxiliary brighteners, such as Ni and/or Co salts, aromatic aldehydes (e.g. anisaldehyde or veratraldehyde) and colloids (e.g. carboxymethyl cellulose or gelatine), and also wetting agents may be added. A specific bath to which oxidized polyvinyl alcohol is added comprises .Cd (as metal).22g/l .Total NaCN.125g/l .Total NaOH.34g/l .NiSO4 6H2O.1.25g/l Cd anodes are used in the Examples. Details of oxidizing the polyvinyl alcohol with H2O2, KMnO4 and K2Cr2O7 are given (see Division C3).ALSO:A water-soluble polyvinyl alcohol is oxidized with H2O2, alkali metal permanganates or alkali metal dichromates. Oxidation can be in a neutral aqueous solution but with H2O2 the solution may be acidified, e.g. with HCl, H2SO4, CH3COOH or HCOOH to accelerate the reaction and with alkali metal permanganate the solution can be acid or alkaline. Specific examples give reaction temperatures of 140 DEG F. and 185 DEG F. Details of Cd electroplating baths employing the oxidized polyvinyl alcohol are given (see Division C7).
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