Effect of Different pH Value on Corrosion Resistance of AZ31B Magnesium Alloy with Ferricyanide Conversion Film

In this work, a chemical conversion film was prepared on the surface of magnesium alloy by chemical impregnation in the conversion solution containing ferricyanide. The surface morphology and composition of the films were studied by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD), and the electrochemical corrosion characteristics of the films were investigated in 3.5% NaCl solution by the electrochemical testing and hydrogen evolution experiment. The results showed that a layer of flake material was formed on the surface of the magnesium alloy, and this film could play a good role in protecting the substrate. By controlling the variable method to further optimize the pH of the chemical conversion solution, it was found that the film had the best corrosion resistance when the pH was 4.