Influence of surface-roughness on the corrosion-fatigue behavior of MAO coated 6061-T6 Al alloy assessed in NaCl medium

Abstract The micro arc oxidation (MAO) coatings corresponding to 50 μm and 90 μm thicknesses were formed on bare and shot-peened Al alloy and then subjected to polishing process. The influence of post-polishing on the resultant corrosion-fatigue life was systematically studied under completely reversed loading (R = −1) for each material condition in 3.5 wt% NaCl corrosion medium. The electrochemical impedance spectroscopy (EIS) and potentio-dynamic polarization (PDP) techniques were utilized to evaluate the corrosion behavior of MAO coatings in 3.5 wt% NaCl solution. The MAO coatings were examined for surface and cross-sectional morphologies, constituting phases were identified, surface-roughness in as coated and polished conditions was evaluated. Further, the fractography studies were also carried out to understand the corrosion-fatigue failure mechanism. The reduced surface roughness had a beneficial role in enhancing overall corrosion-fatigue life of Al alloy.