An eco-friendly Ca Ce and Ca Y based LDH coating on AZ31 Mg alloy: Surface modification and its corrosion studies in simulated body fluid (SBF)

The corrosion resistance of AZ31 is inappropriate, which demands the improvement of the anti-corrosion performances for practical applications. Therefore, environmentally friendly rare earth elements based such as CaCe and CaY layered double hydroxide (LDH) coatings are developed on the AZ31 alloy surface in this work. The coatings are characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and the static sessile drop method as well as electrochemical measurements. The results show that these two kinds of LDH coating can obviously retard the corrosion of AZ31 in simulated body fluid (SBF). Also, precipitation of the corrosion products synergistically improves the self-healing and protection performances. However, the CaY based layers contain some cracks that limit the superior protection performance of the coating. The CaCe based LDH coating shows a significantly enhanced corrosion resistance with the corrosion current density of 0.058 μA·cm−2 which is prepared in the solution containing the Ca and Ce cations with the 2:1 mol ratio. It opens the possibility to improve the service life of AZ31 magnesium alloy in SBF.