Preparation and characterization of calcium phosphate containing coating on plasma electrolytic oxidized magnesium and its corrosion behavior in simulated body fluids

• Published in: Journal of alloys and compounds 2022-03, Vol.896, p.163042, Article 163042
• Main Authors: Zhang, Xue, Cui, Shao-Dong, Zhou, Lin, Lian, Jing-Bao, He, Jiao, Li, Xiao-Wu
• Format: Article
• Language: English
• Subjects: Apatite; Biocompatibility; Biodegradation; Biomedical materials; Body fluids; Ca-P coating; Calcium phosphates; Corrosion; Corrosion currents; Corrosion resistance; Corrosion tests; Degradation; Electrochemical impedance spectroscopy; Hydroxyapatite; In vitro methods and tests; Liquid phase deposition; Magnesium; Nucleation; Phase composition; Plasma electrolytic oxidation; Polarization; Spectrum analysis; Submerging; Substrates; X-ray diffraction
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2021.163042

•Plasma electrolytic oxidation and liquid phase deposition are applied to Mg.•Ca-P solution with pH 5.7 is favorable to the nucleation of OCP on PEO coated Mg.•5.7Ca-P layer induces HA deposition on the PEO coated Mg in vitro.•5.7Ca-P/PEO coating improved the corrosion resistance and decreased the degradation rate of Mg.•PEO layer offers better binding and interfacial stability with Mg and 5.7Ca-P layer in 55 days. [Display omitted] A double layer coating (Ca-P/PEO) was designed to form on pure magnesium. The Ca-P coatings were prepared at three pH values of the solution. The morphology, phase composition, microstructure, corrosion resistance, and degradation properties of the samples were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and in vitro assessments. The XRD results indicate that the 5.7Ca-P coating is mainly composed of octacalcium phosphate (OCP). The potentiodynamic polarization test indicates that the corrosion current density of the 5.7Ca-P/PEO coated Mg is 100 times and 3 times lower than that of uncoated Mg before and after immersion in SBF solution for 168 h, respectively. The 5.7Ca-P coating promotes the nucleation of osteoconductive minerals (i.e., bone-like apatite), and the hydroxyapatite (HA) layer formed on the surface of the 5.7Ca-P coating is dense, thick, and stable after immersion in SBF solution for 30 days. These experimental results have demonstrated that the 5.7Ca-P/PEO coating can introduce a high biocompatibility of the bone-Mg substrate interface and provide long-term stable protection in SBF solution in the initial degradation stage.