Electrodeposition of Ternary Zinc-Nickel-Cobalt Alloys from an Acidic Chloride Bath

摘要

It is well known that alloy coatings on base metal substrates can provide desirable surface properties with respect to corrosion resistance and mechanical properties. Zinc alloy coatings have better corrosion resistance than pure zinc. At present, electrodeposited Zn-Ni (8-20%) alloy coatings have a high technological interest to the automotive industry; however, the binary Zn-Ni thin films, in this range of nickel content, have a dull, gray unattractive finish, and a brightener system is required to obtain bright deposits. Suitable organic bright-eners were developed to produce bright Zn-Ni electrodeposits. Tsuda and Kurimoto found that adding at least 0.05 g/L SrSO_4 to Zn-Ni plating baths produced bright deposits. An upper concentration limit of 10 g/L of SrSO_4 was required to prevent formation of precipitates.