| 摘要 |
<p>Aq. Zn electroplating bath comprises, apart from NaOH, a complexing agent (A) which is the reaction prod. of (poly)phosphoric acid (I) and a cpd. of formula (II). In the formula R is methyl, hydroxymethyl, or H; n =2-4, pref. 2-3 and m=1-5 pref 1-3, x and y are 1 or 2, pref. 1, and z is 0 or 1. Conventional brighteners and wetting agents may be included. Pref. (A) are derived from 0.2-1 mole (I), as P2O5 per OH equiv of (II) and the bath contains 1-10 g/l (A). (A) are replacements for cyanides usually used as complexing and levelling agents. The plated objects do not discolour when subsequently treated in a chromic acid passivating bath.</p> |
