Acta Metall Sin  2017, Vol. 53 Issue (10): 1347-1356    DOI: 10.11900/0412.1961.2017.00248
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Corrosion Behavior of AZ31 Magnesium Alloy in Dynamic Conditions
Linyuan HAN, Xuan LI, Chenglin CHU(), Jing BAI, Feng XUE
School of Material Science and Engineering, Southeast University, Nanjing 211189, China
Abstract

Magnesium alloy is now a promising bio-absorbable material. The previous researches on the corrosion and degradation behavior of biomedical magnesium alloy are mainly carried out in static conditions in vitro. However, considering the real physiological flow field of different flow states in vivo, the static degradation experiments can not effectively simulate the real situation. It is important to study the effect of flow field on the corrosion behavior of magnesium alloy and establish the relationship between flow rate and corrosion rate for the research and development of biomedical magnesium alloy. The corrosion behavior of AZ31 magnesium alloy in the flow field was studied using a self-designed dynamic test bench in vitro by electrochemical measurement, tensile method, pH value test of simulated body fluid (SBF) and SEM observation in this work. The relationship between the corrosion rate of magnesium alloy and the flow rate of the flow field was investigated from the perspective of corrosion electrochemistry. The influence of flow state and flow-induced shear stress (FISS) on corrosion behaviors at different positions of magnesium alloy was also studied by ANSYS finite element analysis. The results show that the flow field will accelerate the corrosion of AZ31 magnesium alloy and the corrosion rate increases with the increase of the flow rate. There is a relationship between the corrosion current density icorr of magnesium alloy and the average flow rate ν during the early corrosion stage, namely $icorr-1=ic-1+Aν-1/2$, where ic is the corrosion current density ignoring the influence of diffusion, and A is a constant. With the corrosion time extended, due to the influence of the corrosion products, the experimental results gradually deviate from the calculated linear relationship of icorr-1-1/2. Also, there are significant differences in the fluid flow state and FISS distributions at different positions of the sample. The mass transfer coefficient at the edge of the sample under different flow rates is 4~5 times bigger than that at the middle position. The localized corrosion morphology corresponds well to the FISS distribution and the difference of flow state.

 ZTFLH: TG146.2
Fund: Supported by National Natural Science Foundation of China (Nos.31570961 and 51771054) and National Key Research and Deve-lopment Program of China (No.2016YFC1102402)