J. Mater. Sci. Technol. ›› 2019, Vol. 35 ›› Issue (6): 1088-1098.DOI: 10.1016/j.jmst.2019.01.006

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Corrosion resistance of in-situ growth of nano-sized Mg(OH)2 on micro-arc oxidized magnesium alloy AZ31—Influence of EDTA

Chang-Yang Lia, Xiao-Li Fana, Rong-Chang Zenga*(), Lan-Yue Cuia, Shuo-Qi Lia, Fen Zhanga, Qing-Kun Hea, M. Bobby Kannanb, c, Dong-Chu Chend, Shao-Kang Guane   

  1. aCollege of Materials Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, China
    b Biomaterials and Engineering Materials (BEM) Laboratory, College of Science, Technology and Engineering, James Cook University, Townsville 4811, Australia
    c School of Engineering, RMIT University, Carlton 3053, VIC, Australia
    d School of Materials Science and Energy Engineering, Foshan University, Foshan 528000, China
    e School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450002, China
  • Received:2018-09-26 Revised:2018-11-08 Accepted:2018-11-26 Online:2019-06-20 Published:2019-06-19
  • Contact: Zeng Rong-Chang
  • About author:

    1 These authors contributed equally to this work.

Abstract:

One of the major obstacles for the clinical use of biodegradable magnesium (Mg)-based materials is their high corrosion rate. Micro-arc oxidation (MAO) coatings on Mg alloys provide mild corrosion protection owing to their porous structure. Hence, in this study a dense Mg(OH)2 film was fabricated on MAO-coated Mg alloy AZ31 in an alkaline electrolyte containing ethylenediamine tetraacetic acid disodium (EDTA-2Na) to reinforce the protection. Surface morphology, chemical composition and growth process of the MAO/Mg(OH)2 hybrid coating were examined using field-emission scanning electron microscopy, energy dispersive X-ray spectrometer, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared spectrophotometer. Corrosion resistance of the coatings was evaluated via potentiodynamic polarization curves and hydrogen evolution tests. Results manifested that the Mg(OH)2 coating possesses a porous nano-sized structure and completely seals the micro-pores and micro-cracks of the MAO coating. The intermetallic compound of AlMn phase in the substrate plays a key role in the growth of Mg(OH)2 film. The current density of Mg(OH)2-MAO composite coating decreases three orders of magnitude in comparison with that of bare substrate, indicating excellent corrosion resistance. The Mg(OH)2-MAO composite coating is beneficial to the formation of calcium phosphate corrosion products on the surface of Mg alloy AZ31, demonstrating a great promise for orthopaedic applications.

Key words: Magnesium alloys, Micro-arc oxidation, Magnesium hydroxide, Coatings, Biomaterials