The influence of organic additives on the electrodeposition of iron-group metals and binary alloy from sulfate electrolyte

Thin films of the iron-group metals Fe and Co and binary CoFe alloy are galvanostatically electroplated from an acid sulfate electrolyte onto a copper rotating disk electrode. The use of organic additives in the electrolyte is widespread to produce thin films by electrodeposition. In the present work, the influence of organic additives containing a similar molecular structure on the anomalous codeposition behavior of the binary CoFe alloy is investigated. The partial current densities of the codepositing metals and of the side reaction in the presence of organic additives are determined from an analysis of the deposit and are compared with those measured for the pure metals and those electroplated without additive. Comparison of the electrodeposition results indicate that codeposition of cobalt and iron metals leads to a reduction of the reaction rate of the more noble component compared and an increase of the reaction rate of the less noble component to single-metal deposition. Organic additives do not affect the CoFe deposition mechanism. However, SAC and PHTA decrease the rate of iron deposition contrary to o-toluene sulfonamide (oTOL).