Effect of coating frequency on the corrosion performance of PEO coatings on AZ31B Mg alloy produced in an electrolyte containing hydroxyapatite nanoparticles

In this study, to improve the corrosion performance, plasma electrolytic oxidation (PEO) coatings on AZ31B Mg alloy in a phosphate-based electrolyte containing hydroxyapatite nanoparticles were investigated. For this purpose, the corrosion behavior of coatings generated at different frequencies (100, 1000, and 2000 Hz) was studied. The influence of coating frequency on the corrosion behavior of the coatings created as well as the microstructure of the coating was investigated. Surface characteristics of the coatings were investigated using scanning electron microscopy and X-ray diffraction pattern. To investigate the corrosion behavior of coatings generated at different frequencies, polarization and impedance spectroscopy tests in simulated body fluid have been studied. The results showed that at a frequency of 1000 Hz, the created coating had a uniform surface with a lower porosity percentage. Also, the results of electrochemical tests showed that the corrosion resistance of the coating created at a frequency of 1000 Hz leads to the lowest corrosion current density (5.83×10-8 A/cm2) in the coating and thus more became the most corrosion resistant.