Fabrication and corrosion resistance of Mg-Fe layered double hydroxide films on pure mg substrates by electric field

The work aims to prepare Mg-Fe hydrotalcite film on the surface of pure magnesium to improve the corrosion resistance in simulated body fluids. Pure magnesium matrix was pretreated in the Fe2+/CO32- solution, and then placed in an alkaline solution with a pH of 10, while the sample was used as an anode and the current was applied to assist film formation. The effect of electric field environment on the quality of the film was studied by controlling the current and formation time. The surface morphology and phase composition of the Mg-Fe hydrotalcite film were characterized by scanning electron microscopy and X-ray diffractometric. The electrochemical experiments (potentiodynamic polarization and electrochemical impedance spectroscopy) were conducted to study corrosion resistance of Mg-Fe hydrotalcite film. Mg-Fe hydrotalcite film was prepared on pure magnesium surface under different electric field conditions. As the current increased and the time prolonged, the film quality and corrosion resistance increased first and then decreased. When the current was 50 mA and the time was 1 h, the prepared film had the best quality and corrosion resistance. The electric field environment could effectively promote the reaction, greatly shorten the time and improve the preparation process. The corrosion current density of the sample prepared under the optimum process conditions was 9.24×10-6 A/cm2, which was about 1/10 of the pure magnesium matrix (1.09×10-4 A/cm2). The Z modulus was about 2410 Ω·cm2, which was about 4 times that of the substrate (668 Ω·cm2). The Mg-Fe hydrotalcite film is successfully prepared on the surface of pure magnesium by electric field assisted process. The preparation time of the film can be shortened by this process, and the prepared film layer can effectively improve the corrosion resistance of the pure magnesium matrix in the simulated body fluid. © 2019, Chongqing Wujiu Periodicals Press. All rights reserved.