Cu-Mn electrodeposition from simple sulfate electrolytes with the only addition of ammonium sulfate was studied under different current densities, at pH 2.6-2.8 and pH 6.4-6.6, and at different cupric ion concentrations. An electrochemical investigation of this Cu-Mn electrodeposition system was conducted by potentiodynamic methods and cyclic voltammetry. Electrodeposition was performed galvanostatically. Mn content in the alloy increased with increasing current density. Three types of coatings were obtained: spongy Cu-rich oxygen-containing films at low current density, crystalline Mn-rich coatings at intermediate current density (type I), and amorphous coatings at high current density (type II). At high pH (6.4-6.6), the composition of type I coatings could be controlled by adjusting the current density, while at low pH (2.6-2.8) composition becomes more controllable by varying the Cu2+ concentration ([Cu2+]). The optimal current density to obtain type I coatings is shifted upward with increasing [Cu2+]. A Cu-rich interlayer is formed between the Cu-Mn film and the stainless steel substrate. The bulk of type II coatings is mainly composed of metallic Cu and Mn. Metal complexation equilibria with NH3 can explain the influence of Cu additions on coating morphology and composition. (C) 2004 The Electrochemical Society.