One-pot scalable in situ growth of highly corrosion-resistant MgAl-LDH/MBT composite coating on magnesium alloy under mild conditions

• 作者: Ting Hu Yuejun Ouyang Zhi-Hui Xie Liang Wu
• 来源期刊: 材料科学技术（英文版）
• 年，卷（期）: 2021,（33）
• 页码范围: 225-235
• 页数: 11页
• 语种: 英文

摘要

Current corrosion-resistant layered double hydroxide(LDH)coating on Mg alloy is usually in situ grown in autoclave by hydrothermal methods under high temperature and high-pressure conditions,which is unfavorable for industrial application.We report that an inhibitor(2-mercaptobenzothiazole,MBT)incor-porated composite(MgAl-LDH/MBT)coating can be in situ deposited on bare AZ31 Mg alloy surface with the assistance of a chelating agent(ethylenediaminetetraacetic acid)under a relatively low temperature(95℃)and ambient pressure by a one-pot method.The successful formation of LDH/MBT composite coating is confirmed by a series of characterizations,such as X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and energy dispersive spectroscopy(EDS).The corrosion resistance of the compos-ite coating is evaluated by means of hydrogen evolution measurement,electrochemical impedance spec-troscopy(EIS),Tafel polarization curves,and neutral salt spray test.The tests show that the LDH/MBT composite coating has a very low corrosion current density(1.73 10-8 A cm-2),an extremely high charge transfer resistance(2.336 MΩ cm2),and does not show any corrosion pits even after 15 d of exposure to a NaCl solution or 7 d of exposure to salt fog environment,manifesting the good and robust corrosion protection.Lastly,the deposition and corrosion protection mechanisms of the MgAl-LDH/MBT composite coating are also discussed and proposed based on the EDS characterization of the coating after long-time exposure.