Electrochemical Corrosion Behavior of Micro-arc Oxidation Ceramic Coatings on 2A12 Aluminum Alloy

The electrochemical corrosion behaviors of the micro-arc oxidation (MAO) coatings with different thicknesses were evaluated by electrochemical methods. The results show that corrosion resistance of MAO ceramic coatings is significantly dependent on coating thickness, and with the thickness increase, corrosion resistance increases. The corrosive potential of the reverse-scanning curve is gradually higher than that of positive scanning with the increase of MAO treatment time, which illustrates that there is no corrosion tendency, MAO coating surface is re-passivated and anti-pitting corrosion resistance is enhanced. The surface impedance distribution maps of MAO ceramic coatings were obtained by LEIS ( Local Electrochemical Impedance Spectroscopy) technology. It is shown that the impedance is not uniform and is as same as surface morphology, and the impedance range was from 1.0×104 Ω to 8.0×104 Ω for the MAO ceramic coating after 60 min treatment, from1.8×105 to 1.4×106 Ω for the MAO ceramic coating after 90min treatment, indicating that the impedance increases with MAO treatment time.