Acid zinc sulfate. Anthranilic acid and formaldehyde brighteners

A study was made on the use of anthranilic acid and HCHO as brighteners in acid Zn electroplating. The bath contained: ZnSO4.7H2O 165, Al2(SO4)​3.16H2O 30, H3BO3 30 and NaCl 15 g​/L. A 99.9​% Zn sheet was used as the anode. The bath was bubbled with air, N or O and was operated at 25-​30° and pH 2.5. To improve the plates poly(vinyl alc.) in combination with dextrin was used and a fine grained plate was obtained. A concn. of 0.75 g​/L of anthranilic acid gave the widest possible brightness range and a combination of this acid with HCHO gave good, satisfactory, mirror-​bright Zn plates over a wide range of c.ds