Electropolymerization of aniline on an iron disc electrode in aqueous solutions is studied by using various inorganic and organic acids under potentiodynamic, potentiostatic and galvanostatic conditions. Smooth, well adhering polyaniline coatings were obtained in oxalic acid solutions under potentiodynamic conditions during sequential scanning of the potential region between -0.6 and 1.5 V. Well-defined cyclic voltammograms showing the electroactivity and growth of polyaniline were observed during each cycle. The deposited coatings were characterized electrochemically, microscopically and spectroscopically. The deposition of polyaniline appears to occur over the passive metal oxide film, but electron transfer between the polymer and the metal can occur. Polyaniline coatings on iron appear to be promising for metal anodic protection in corrosive aqueous media.