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.

For the AZ31 Mg alloy, the Nyquist plot for the sample with 1 h, 4 h, 8 h immersion treatment consists of three loops, which can be considered as the primary immersion stage. When AZ31 Mg alloy was exposed in 0.1 mol/L NaCl solution for 24 h, the inductive loop disappeared, which was attributed to the appearance of corrosion pit during the late stage of immersion timeFigure optionsDownload full-size imageDownload as PowerPoint slide