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A hydrophobic surface was successfully fabricated on the Mg-Al-layered double hydroxide (Mg-Al LDH)/Mg(OH)2-coated AZ31 magnesium alloy via an in-situsteam coating (SC) process and a subsequent surface modification with environment-friendly myristic acid (MA). The microstructure, composition and hydrophobicity of SC/MA composite coating were investigated by XRD, SEM, EDS, FTIR, and contact angle (CA) measurement. The corrosion behavior of the hybrid coating was evaluated by potentiodynamic polarization, EIS and hydrogen evolution test in 3.5 wt.% NaCl solution. The results showed that the LDH coating had nano-flake microstructure, which remained unchanged after modification with MA. The CA of the MA-modified coating surface reached up to 129°± 3.5°, and the corrosion current density of SC/MA-2 coating decreased about three orders of the magnitude compared to that of the substrate. It is proven that the modified surface has an effective anti-corrosion effect on AZ31 alloy. The formation mechanism and the corrosion mechanism of the coating were also discussed.

Biodegradable Mg alloys have generated great interest for biomedical applications. Accurate predictions of in vivodegradation of Mg alloys through cost-effective in vivoevaluations require the latter to be conducted in an environment close to that of physiological scenarios. However, the roles of glucose and buffering agents in regulating the in vivodegradation performance of Mg alloys has not been elucidated. Herein, degradation behavior of AZ31 alloy is investigated by hydrogen evolution measurements, pH monitoring and electrochemical tests. Results indicate that glucose plays a content-dependent role in degradation of AZ31 alloy in buffer-free saline solution. The presence of a low concentration of glucose, i.e. 1.0 g/L, decreases the corrosion rate of Mg alloy AZ31, whereas the presence of 2.0 and 3.0 g/L glucose accelerates the corrosion rate during long term immersion in saline solution. In terms of Tris-buffered saline solution, the addition of glucose increases pH value and promotes pitting corrosion or general corrosion of AZ31 alloy. This study provides a novel perspective to understand the bio-corrosion of Mg alloys in buffering agents and glucose containing solutions.