| LI Hao,ZHANG Hao,SHEN Xiao-long,LI Dong-liang,YANG Cheng.Corrosion Resistance of Anodic Oxidation/Polyphenol Conversion Composite Coating on Biomedical Magnesium Alloy[J],52(1):196-205 |
| Corrosion Resistance of Anodic Oxidation/Polyphenol Conversion Composite Coating on Biomedical Magnesium Alloy |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.01.020 |
| KeyWord:magnesium alloy biomedical material anodic oxidation EGCG corrosion resistance |
| Author | Institution |
| LI Hao |
College of Vanadium and Titanium,Sichuan Panzhihua , China |
| ZHANG Hao |
College of Vanadium and Titanium,Sichuan Panzhihua , China |
| SHEN Xiao-long |
College of Biology and Chemical Engineering, Panzhihua University, Sichuan Panzhihua , China |
| LI Dong-liang |
College of Vanadium and Titanium,Sichuan Panzhihua , China |
| YANG Cheng |
College of Vanadium and Titanium,Sichuan Panzhihua , China |
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| Abstract: |
| Magnesium and its alloys are widely regarded as potentially revolutionary orthopaedic implant materials due to their biodegradability, good biocompatibility and ideal Young's modulus close to that of natural cortical bone. However, the clinical application of magnesium implants is limited by their high reactivity in the physiological environment. Rapid degradation of magnesium alloys in physiological environments can lead to rapid loss of implant mechanical integrity, large amounts of hydrogen, localized alkaline environments, and enrichment of corrosion products. To address these issues and develop clinically viable magnesium-based bone implants, slowing and controlling the biodegradation rate of magnesium- based bone implants is critical. The work aims to prepare an anodic oxidation/polyphenol conversion composite coating on AZ31 Mg alloy surface to solve the problems such as fast degradation and easy to cause inflammation of medical magnesium alloy in implantation environment. In this work, an anodic oxidation/polyphenol conversion composite coating was prepared on AZ31 alloy, and its corrosion resistance and was evaluated. Anodic oxidation (OA) coating was prepared by anodization method, then a polyphenol conversion coating was prepared on the OA coating by immersing in EGCG (epigallocatechin gallate) solution, and finally the OA-EGCG composite conversion coating was obtained. The surface morphology and composition structure of the coating were analyzed by SEM, EDS, XRD, FTIR and XPS. The polarization curve, electrochemical impedance spectroscopy, and long-term immersion test were used to evaluate the corrosion resistance of the composite coating. The results showed that the main components of anodic oxide coating were MgO and MgSiO3. After the EGCG conversion coating constructed, the porous morphology of the AO coating was filled. The characteristic peaks of EGCG appeared in the FTIR spectrum, indicating the successful construction of the OA-EGCG composite coating. The fitting results of XPS high-resolution images of Mg and O elements on the AZ31-AO-EGCG showed that the EGCG was combined on the AZ31-AO surface by conversion to form an AO-EGCG composite coating. The anodic oxide coating acts as an intermediate layer, which can effectively improve the binding force of the EGCG conversion coating to the substrate. Electrochemical evaluation results showed that the corrosion current density of OA-EGCG coating was reduced about 2 orders of magnitude compared with AZ31. The arc radius of the high-frequency capacitive reactance was significantly increased, and the polarization resistance (Rp) obtained after the equivalent circuit simulation was 179.425 kΩ.cm2, which was much larger than that of the AZ31. After immersion for 160 h, the OA-EGCG composite coating could obviously control the increase of pH value of the solution, and significantly lower than other controls. The corrosion products formed on the AZ31-OA-EGCG was the least. The hydrogen evolution results showed that the AZ31 released about 14 mL/cm2 of hydrogen within 160 hours, and the AZ31-AO and AZ31-AO-EGCG sample groups released about 11 mL/cm2 and 6 mL/cm2 of hydrogen, respectively. This result corresponded to the immersion changes in pH. By combining the anodization and the polyphenol conversion coating, the corrosion resistance of the single anodized coating was improved, and the bonding force of the single polyphenol coating was improved. |
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