The corrosion resistance of LDH coatings constructed via electrodeposition technique on AZ31B
Aiming at improving the corrosion resistance of AZ31B magnesium alloy,thein-situ electro-chemical deposition process parameters of Mg-Allayered double hydroxide(LDH)coating was optimized.Different concentrations of electrochemical deposition solutions were prepared,and a layer of LDH coating was deposited on the surface of AZ31B by in situ electrochemical deposition method,and SA-LDH composite coating was obtained after modification with stearic acid.The microstructure and chemical composition were tested and analyzed,the corrosion resistance of the coating was charac-terized by electrochemical polarization and alternating impedance(EIS)experiments,so the influence of the preferred electrochemical deposition process on its microstructure properties was determined.The results show that the preferred solution concentration is 0.05 mol/L,and the surface of the obtained coating is porous and well combined with the matrix.The X-ray diffraction(XRD)pattern showed two characteristic peaks of LDH(003)and(006).The polarization curve results showed that the corrosion current density of LDH coating was 9.21×10-6 A/cm2,which was reduced by two orders of magnitude compared with uncoated magnesium alloy,and the corrosion potential of SA-LDH coating increased to-1.33 V.The AC impedance of LDH coating after immersion in 3.5 wt.%NaCl solution showed an increase in impedance modulus and frequency,showing good corrosion resistance.By adding stearic acid,a superhydrophobic film can be formed on the coating surface,which can effectively hinder the penetration and erosion of AZ31B magnesium alloy by the corrosive medium Cl-.
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