Corrosion Protection Comparison of a Chromate Conversion Coating to a Novel Conductive Polymer Coating on Aluminum Alloys

Abstract Comparisons of the corrosion resistance performance of a novel polyaniline based double strand conductive polymer coating versus a chromate conversion coating on two aluminum alloys were made. Potentiodynamic scans, electrochemical impedance spectroscopy (EIS) in 0.5N NaCl solutions and ASTM B-117 salt spray tests were performed on coated samples of AA7075-T6 and AA2024-T3 aluminum alloys. Results show the conductive polymer film offers, at the least, an equivalent protection performance as the chromate coating with a two order of magnitude reduction in corrosion current densities in cyclic polarization tests, near equivalent impedance values and less undercutting of a scribed area in salt spray test samples. In an acidic salt solution of pH 3.6, the conductive polymer offers an improved performance with a one order of magnitude higher impedance over the chromate coatings.