Alloying and brushite coating improve corrosion resistance of magnesium in a simulated physiological environment

Abstract

Abstract While magnesium (Mg) and its alloys have been regarded as encouraging orthopaedic implant materials, the high corrosion rate limits their application. This study determines how alloying and brushite coating affected the corrosion rate of Mg in vitro. The corrosion behaviours of pure Mg, Mg-Nd-Zn-Zr alloy (Jiao Da Bio-Mg, JDBM) and brushite coated JDBM in a simulated physiological environment were comparatively evaluated. The evaluation included the surface morphology, roughness, chemical composition, structure, phase composition and functional groups of the corrosion products with the corrosion rate, pH value, Mg2+ concentration and osmotic pressure of the immersion solution. The following corrosion resistance trends were found: brushite coated JDBM\u202f>\u202funcoated JDBM\u202f>\u202fpure Mg. The main corrosion product of the Mg alloys in the cell culture medium was MgCO3·3H2O. Compared with the pure Mg, the corrosion form of the JDBM alloys was uniform corrosion. The results showed that the addition of the Nd, Zn and Zr elements and brushite coating effectively improved the corrosion resistance of metal Mg. In addition, the power law function formula Δm = ρAtB was applied successfully to predict the mass loss of the JDBM alloy in an in vitro immersion test.