Brightening composition for acid zinc electroplating bath and process

Claim 1

An aqueous zinc electroplating bath having a pH of about 0 up to about 6.5 containing an effective amount of a mixture of (a) a primary brightener comprising a polymer selected from the group consisting of polyacrylamide polymers and N-substituted polyacrylamide derivatives and copolymers thereof of the formula: ##STR6## wherein: Y may be the same or different and is R or RX, where R is H or C 1-10 aliphatic radical, where X is H, OH, COOR 1 , COON[R 1 ] 2 , SO 3 M, CN, N[R 1 ] 2 or OR, where M is H or a Group I or II metal; R 1 is H or C 1-2 alkyl radical; and n is 2 to 2,000,000, and copolymers of said polymer and a solubilizing agent present in an amount up to 25 mole percent of the copolymer selected from the group consisting of methacrylic acid, acrylic acid, acrylonitrile, methacrylonitrile, vinyl C 1-5 alkyl esters, vinyl halide, eiphalohydrin, vinylidine halide, alkylene oxide and mixtures thereof; and (b) a secondary brightener and mixtures thereof selected from the group consisting of boric acid and Group I and II metal salts thereof; and/or thiourea and N-substituted derivatives thereof of the formula: ##STR7## wherein: Z may be the same or different and is R 2 or R 2 X 1 , where R 2 is H, C 1-8 aliphatic radical, C 6-10 aryl radical, C 5-9 heterocylic nitrogen radical; where X 1 is H, OH, COOR 3 , COON[R 3 ] 2 , SO 3 M 1 , CN, N[R 3 ] 2 , OR 3 , or PO 4 M 1 , where R 3 is H or C 1-2 alkyl radical and M 1 is H or a Group I or II metal, and where Z on one N can form a cyclic with Z on other N; and further including the sulfur adducts of said thiourea and N-substituted derivatives thereof selected from the group consisting of propane sultone, haloacetic acid, halosulfonic acid, and mixtures thereof.