The influence of EDTA‐2Na on microstructure and corrosion resistance of PEO coating for AA1060 alloy

In this study, plasma electrolytic oxidation (PEO) process was applied to AA1060 aluminum alloy in an alkaline‐based electrolyte with different concentrations of EDTA‐2Na. The investigation of coatings was concentrated on sparks, phase, structure, morphology, and corrosion resistance. The whole process presented a “soft spark” regime which proved by the reduction of light and acoustic emission with increase of current. The results of SEM and EDS showed that more discharge channels were found under surface and the proportion of silicon in the inner layer increased for the sample treated in solution with 5 g/L EDTA‐2Na, which was attributed to D type discharge causing some light emission invisible on sample surface. The polarization test presented a better corrosion resistance with the increase of EDTA‐2Na. However, EIS measurement showed a bigger corrosion resistance for outer layer of sample prepared with the addition concentration up to 3 g/L that meant outer layer played a more critical role in terms of corrosion resistance.