Electrodeposition of polypyrrole on iron from aqueous solutions of pyrrole and oxalic acid yields strongly adherent, smooth polymer layers. The electrochemical process proceeds at a constant current density of 2mA cm(-2). The potential-time curve is characterized by a short induction period, where active iron dissolution occurs. The perfect performance of the polymer coating is attributed to the formation of an iron(II) oxalate interlayer. The influence of current density, pyrrole concentration and KNO3 addition on the electrodeposition process and the electrochemical and physical properties of the layers are studied in detail.