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Abstract

An aqueous acidic plating bath for the electrodeposition of a bright zinc deposit on a substrate is disclosed and comprises zinc ions, and an amount sufficient to provide a level and bright zinc electrodeposit, of a polymeric sulfur-containing compound having the general formula RS(R'O--.sub.n H, or (I) (S[(R').sub.n H].sub.2 (II) wherein R is an alkyl group containing up to about 24 carbon atoms, each R' is independently an alkylene group containing 2 or 3 carbon atoms and each n is independently an integer of from 1 to about 100. Additionally, the plating baths of the invention may contain at least one aromatic carbonyl-containing compound and particularly aromatic aldehydes and aromatic carboxylic acids. Aromatic sulfonic acids and ethylene oxide condensates of such sulfonic acids also are useful in the plating baths of the invention. Other ethylene oxide condensates can be included in the baths including those derived from carboxylic acids, amides, amines, alcohols, phenols and naphthols. Methods for depositing bright zinc coating over a wide range of current densities, and additive compositions for preparing plating baths useful in these methods also are described.

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First Claim