The effect of Fe3+ concentration on saturation magnetic flux density (B-s) of electrodeposited Co40-44Fe60-56 films was investigated. The results show that if the conditions at the electrochemical interface for nucleation/precipitation of iron(III) hydroxide (Fe(OH)(3)) are reached, the B-s of electrodeposited Co40-44Fe60-56, films quickly decreases as a result of the Fe(OH)(3) incorporation into deposit. These conditions are discussed as a function of the Solution formulation (pH) and the parameters of electrodeposition process (current density, current efficiency, diffusion layer thickness) and a simple analytical model is developed qualitatively describing the hydroxide incorporation phenomenon and resulting decrease in B-s of Co40-44Fe60-56 films. Published by Elsevier Ltd.