Corrosion Resistances Feature of Polyaniline Film

A suggest has been advanced on using simultaneously the electrical conductivity and chemical and electrochemical stability of polyaniline for protecting metal conductive materials. The conditions for polymerizing compact and conductive polyaniline films were explored by electrochemical methods on a stainless steel anode in acidic aqueous solution. The polyaniline films obtained don't dissolve in NaOH or NaCl aqueous solution. The corrosion resistances of the polyaniline modified stainless steel were measured through polarization curves. In comparing polyaniline modified stainless steel specimens with unmodified ones the corrosion potentials in 3% NaCl and H₂SO₄ aqueous solution remarkably moved about 0.2-0.7 V towards the positive direction and were positive vs. saturated calomel electrode. The corrosion current densities were lower than those of 304 stainless steel and carbon steel about three orders of magnitude. The polyaniline layer would dissolve and fall off because of over-oxidation when the potential arose to 0.65V (in 3% NaCl aqueous solution) or 0.9V (in 0.5mol/l H₂SO₄). In 1mol/l HCl aqueous solution the polyaniline film was not able to offer protection for stainless steel specimens.