Corrosion protection of AA6061 T6 by fluoropolymer coatings in NaCl solution

The corrosion protection performance of epoxy-treated fluoropolymer-coated AA6061 T6 alloy was studied. Two types of fluoropolymer with different fluorine ratios (FLBZ 1074 and modified FLBZ 1074) were applied as top coatings. Electrochemical impedance spectroscopy (EIS) was used to investigate the corrosion resistance of such coatings in 3.5% NaCl solution under uniform and scratched conditions. Uniform coatings showed excellent corrosion protection even after 4 months of immersion in NaCl. Conversely, the corrosion rates increased dramatically under the scratched conditions after less than 1 month of immersion in NaCl due to filiform corrosion. A general equivalent circuit model has been used to analyse the impedance data in terms of reactions occurring during the interaction of the coated specimens with the environment. Based on the results of this analysis, together with the visual inspection, FLBZ 1074 coating was found to be more efficient than the modified FLBZ 1074 coating in providing corrosion protection in NaCl.