Corrosion protection of AZ31 magnesium alloy treated with La3＋ modified 3-methacryloxypropyltrimethoxysilane conversion film

This study demonstrated the influence of addition concentration of La3+ on the anti-corrosion behavior of a 3-methacryloxypropyltrimethoxysilane(MPS) film formed on AZ31 magnesium alloy. The morphology and surface chemistry of the samples were evaluated through scanning electron microscopy(SEM) and Fourier transform infrared spectroscopy(FT-IR), respectively. The corrosion resistance of the pre-treated AZ31 magnesium alloy was studied during immersion in 0.1 mol/L NaCl solution, using potentiodynamic polarization curves and electrochemical impedance spectra(EIS). In comparison to MPS film, the low concentration of La3+ ion modified silane layer exhibited a better anti-corrosion performance, nevertheless, the high concentration of La3+ ion modified was worse. Results showed that the preferable addition concentration of La3+ ion in the silane film was 5×10–4 mol/L in this experiment.