The codeposition behavior of three alloy systems, FeNi, FeCo, and CoNi, was studied in acid sulfate electrolytes using rotating cylinder electrodes to control mass transport conditions. The partial current densities of the codepositing metals and of the side reaction were determined from an analysis of the deposit and were compared with those measured for the pure metals deposited under identical conditions. Results confirmed that Ni is inhibited by the presence of Fe2+ and Co2+ ions. Fe deposition rate is enhanced by the presence of Co2+ and Ni2+ ions. The ion of the less noble metal has a stronger influence on the deposition behavior of the partner ion. Co is inhibited by codeposition of Ni2+ ions and enhanced by Fe2+ ions. The present data demonstrate that anomalous codeposition of iron group metals involves both inhibiting and accelerating effects.