MgAl Layered Double Hydroxide Nanoplate Coatings as Corrosion Inhibitors for Long-Term Protection of Q235 Steel

Layered double hydroxides (LDHs) have an excellent barrier and Cl- adsorption energy. Although LDH directly grown on the surface of steel plate can effectively delay metal corrosion, the shortcoming of poor stability and short life still needs attention. In this study, MgAl-LDH nanoplate conversion coating was grown on the surface of Q235 steel in situ and sodium phosphate (SP) corrosion inhibitor was loaded by vacuum impregnation. The electrochemical test proved the excellent corrosion inhibition effect of LDH nanofilm. Compared with the blank sample, the impedance modulus of EP/Mg-Al@SP is increased by 50%. To improve the stability of MgAl-LDH nanoplate coating, layered double hydroxide (LDH) was covered with epoxy resin to form the EP/Mg-Al@SP composite coating system. Compared with EP coating, the corrosion inhibition effect of EP/Mg-Al@SP is improved by 44%, and the wear resistance coefficient of EP/Mg-Al@SP LDH is reduced by 23%. The electrochemical test shows that the impedance modulus of EP/Mg-Al@SP is 3 orders of magnitude higher than that of EP coating. The design of double-layer system of LDH and epoxy resin not only shows remarkable long-term corrosion resistance, but also provides reference and thinking for the compounding of organic and inorganic coatings.