Effect of Magnesium Phosphate Anodizing Electrolyte on Corrosion Resistance of Aluminum Alloy

Anodizing is one of the methods to improve the corrosion resistance of aluminum alloy. Anodic oxide film was prepared on 2024 aluminum alloy by constant current anodic oxidation method. The selected electrolyte was tartrate-sulfuric-acid electrolyte which adding magnesium phosphate. Anodic oxide film was prepared by changing the anodic oxidation temperature, current, time and other process parameters. The morphology, elemental composition and phase of anodic oxide film before and after optimization were characterized by SEM (scanning electron microscopy), XRD (X-ray diffraction) and EDS (energy dispersive spectroscopy), the corrosion resistance of anodic oxide film was characterized by electrochemical test, salt spray experiment and immersion aging experiment. The results showed that the thickness of the film after adding magnesium phosphate was higher than that before adding magnesium phosphate. Electrochemical impedance spectroscopy showed that the impedance modulus at 0.01 Hz is one order of magnitude higher after adding magnesium phosphate than before adding magnesium, and two orders of magnitude higher than the bare substrate, indicating that the corrosion resistance was greatly enhanced. The anodic oxide film obtained by adding magnesium phosphate to the electrolyte greatly improved the corrosion resistance, which provide an effective idea for the corrosion protection of aluminum alloy