Role of incorporation of ZnO nanoparticles on corrosion behavior of ceramic coatings developed on AZ31 magnesium alloy by plasma electrolytic oxidation technique

Improvement of corrosion resistance is one of the main goals in developing plasma electrolytic oxidation (PEO) ceramic coatings on AZ31 magnesium alloys. In this study, ceramic coatings were deposited on AZ31 magnesium alloys by PEO technique in electrolytes containing 10 g/l sodium phosphate (Na3PO4) and 1.5 g/l sodium hydroxide (NaOH) at different concentrations of ZnO nanoparticles and current density of 7.1 A/dm(2) for 10 min. To investigate the corrosion behavior of the samples, they were placed in Hank's solution, while Tafel polarization and electrochemical impedance spectroscopy (EIS) were used. X-ray diffraction (XRD) together with field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy (EDS) techniques were employed to investigate the coatings. XRD results showed that the prepared PEO layers mainly consist of ZnO, Mg, and Mg-3(PO4)(2) phases. Corrosion test results showed that the use of ZnO nanoparticles improved the corrosion resistance of PEO ceramic coatings in Hank's solution. In contrast, the best result was obtained by using the electrolyte containing 6 g/l ZnO nanoparticles with a corrosion current density of 0.08 mu A/cm(2) and corrosion potential of-1.4615 V-Ag/AgCl. Also, EIS results showed the corrosion resistance of the mentioned coating as 1.05 x 10(6) Omega.cm(2).

Automated summary

Ceramic coatings were deposited on AZ31 magnesium alloys using PEO technique, and the addition of ZnO nanoparticles improved the corrosion resistance of the coatings in Hank's solution. The best results were obtained with an electrolyte containing 6 g/l ZnO nanoparticles, showing a corrosion current density of 0.08 mu A/cm(2) and a corrosion potential of -1.4615 V-Ag/AgCl. Additionally, EIS results indicated a corrosion resistance of 1.05 x 10(6) Omega.cm(2) for the mentioned coating.