Corrosion resistance and ion exchange properties of montmorillonite film on AZ31 in SBF solution

Abstract

Montmorillonite (MMT) film was prepared on the surface of alkali-heat treated Mg alloys by one-step hydrothermal method. The structure and composition of MMT film were characterized using scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The corrosion resistance of MMT film in simulated body fluid (SBF) was investigated using electrochemical tests and immersion experiments. The experimental results showed that with the extension of hydrothermal time, the corrosion resistance of film increased and then decreased. With the increase of MMT powder mass fraction in precursor solution, the corrosion resistance of films also increased and then weakened. The best performance of MMT films was obtained at hydrothermal time of 12 h and MMT powder mass fraction of 2 wt%, with an impedance value of 9.77×106 Ω·cm2, which is an improvement of four orders of magnitude compared to substrate, and the efficiency of corrosion protection was up to 100%. The ion exchange properties, barrier effect and inertness characteristics of MMT provide excellent corrosion protection for magnesium substrates. This study provides a new coating strategy for the preparation of biodegradable magnesium alloys with excellent corrosion resistance and biocompatibility for use as biomedical materials.