Effect of Fe <sup>3+</sup> and F <sup>−</sup> on black micro‐arc oxidation ceramic coating of magnesium alloy
Zhenqian Zhang, Fei He, Changxu Huang, Zekai Song, Jinxiao Yang, Xudong Wang
Abstract
Abstract This study focuses on a black micro‐arc oxidation ceramic coating prepared on the surface of magnesium alloy by the technology of micro‐arc oxidation in the electrolyte containing F – and Fe 3+ as well as its mechanism of F – and Fe 3+ . It needs coatings to experience detail analyses on their thickness, roughness, corrosion resistance, thermal control property, valence states of elements, phase composition, and morphology of coatings, respectively, through coating thickness gauge, roughness tester, electrochemical workstation, AE radiometer, X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD), scanning electron microscope (SEM), and energy‐dispersive X‐ray spectroscopy (EDS). Results showed that with the help of F – in electrolyte, Fe 3+ can be complexed and MgF 2 can be obtained in the coating, which reduces the pores on the surface of micro‐arc oxidation coating. In addition, Fe 3+ in the electrolyte contributes to the preparation of Fe 2 O 3 and Fe 3 O 4 in the coating, which can blacken the surface of the coating. Both F – and Fe 3+ benefit to improve the corrosion resistance and thermal control performance of micro‐arc oxidation coating. There is higher iron oxide in the outer layer but higher fluoride in the inner layer of the coating.