Mackinawite films have been deposited on Ti supports from aqueous solutions containing ferrous and thiosulphate ions, using a potentiostatic double pulse technique. Studies on the influence of the electrolyte concentration ratio [S2O32-]/[Fe2+] on the film properties were performed. Cyclic voltammetry was used as a diagnostic technique for the electrodeposition process. In situ characterisation of the deposits was performed by anodic stripping analysis. The structure and morphology of the films were investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). The experimental data provide evidence that Mackinawite deposits have been obtained from the entire electrodeposition baths although its purity is conditioned by the bath composition. Namely, when [S2O32- ] = [Fe2+], oxidation products such as alpha-S and gamma-FeOOH were detected. (C) 2004 Elsevier Ltd. All rights reserved.