Abstract
For the purpose of detecting the influence of grain structure of a Mg matrix on the microstructure and corrosion resistance of micro-arc oxidation (MAO) coating, prior to MAO processing, sliding friction treatment (SFT) was adopted to generate a fine-grained (FG) layer on coarse-grained (CG) pure Mg surface. It showed that the FG layer had superior corrosion resistance, as compared to the CG matrix, owing to the grain refinement; furthermore, it successfully survived after MAO treatment. Thus, an excellent FG-MAO coating was gained by combining SFT and MAO. The surface morphology and element composition of FG-MAO and CG-MAO samples did not show significant changes. However, the FG layer favorably facilitated the formation of an excellent MAO coating, which possessed a superior bonding property and greater thickness. Consequently, the modified FG-MAO sample possessed enhanced corrosion resistance, since a lower hydrogen evolution rate, a larger impedance modulus and a lower corrosion current were observed on the FG-MAO sample.
Highlights
Commercial pure Mg and its alloys show enormous application potential in automotive, aviation and electric component fields, because of such factors as low density and excellent machinability [1,2,3]
A 900 μm thick deformation layer is prepared on sliding friction treatment (SFT) sample surface where grain sizes are refined
After SFT pretreatment, a 900 μm thick deformation layer was prepared on pure Mg surface, in which the grain size was refined to the fine‐grained level due to high strains in the SFT process
Summary
Commercial pure Mg and its alloys show enormous application potential in automotive, aviation and electric component fields, because of such factors as low density and excellent machinability [1,2,3] They are current prospective implant materials in orthopedics because of favorable biocompatibility, and a similar elastic modulus to that of human bone tissue [4,5,6]. Numerous surface coating methods have been explored on Mg to enhance the anti-corrosion property [7,8,9,10,11,12] In these methods, micro-arc oxidation (MAO) is a promising technique that could generate a protective ceramic coating in a suitable electrolyte [10,12,13,14,15]. Many researchers confirm that increasing the defects (e.g., grain boundary, vacancy and dislocation) density of the substrate helps to accelerate coating growth
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