High corrosion protection of a polyaniline/organophilic montmorillonite coating for magnesium alloys

Epoxy coatings containing polyaniline (PANI) and polyaniline/organophilic montmorillonite (PANI/OMMT) powders were prepared on the surface of AZ91D magnesium alloy. The corrosion performance of the coatings was evaluated by electrochemical impedance spectroscopy (EIS) and open-circuit potential analysis in 3.5% NaCl. The results indicate that the PANI/OMMT coating retained its high corrosion protection for AZ91D magnesium alloy after 6000 h of immersion. The protective mechanism conferred by the PANI/OMMT coating was also discussed. The effects of oxygen on the protective mechanism of PANI were evaluated by EIS measurements in a 3.5% deaerated NaCl solution.

► Epoxy coating containing PANI/OMMT powders retained its high corrosion protection for AZ91D after 6000 h immersion in 3.5% NaCl solution. ► The protective mechanism of PANI/OMMT coating may be explained with the improved barrier ability of the coating by OMMT and the formation of an oxide layer by PANI. ► The corrosion protection of PANI for magnesium alloy decreased in the absence of O2.