Electrochemical Behavior of SiC-coated AA2014 Alloy Through Plasma Electrolytic Oxidation

In this study, AA2014 aluminum alloys were coated with a layer containing silica (SiC) formed by the plasma electrolytic oxidation (PEO) process. The PEO process was performed with different electrical parameters (frequency, current mode, and duty ratio) and with and without SiC to investigate the microstructural and electrochemical differences in the coated samples produced from the process. The microstructure and composition of the PEO coatings were studied by X-ray diffraction (XRD) and a scanning electron microscope (SEM) equipped with an energy dispersive spectroscope (EDS). A potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical behavior of the AA2014 PEO coated samples. The potentiodynamic polarization shows that the SiC PEO-coated samples have a significantly decreased corrosion rate (99.8 %) compared to the un-coated AA2014 Al alloy. Results showed that the coats containing SiC possess much higher corrosion resistance than the un-coated AA2014 Al alloy (8344673%), and the SiC-free coatings – which possess low corrosion resistance – because of their higher chemical stability and more compact microstructure.