Improved electrochemical behavior of Mg-Li alloys by superhydrophobic layered double hydroxides/Ni-based composite coatings

As a lightweight material, the wide application of Mg-Li alloy is restricted by its corrosion resistance. Focusing on this, an innovative superhydrophobic composite coatings of nickel-based metal coupled with layered double hydroxides (LDHs) was prepared on Mg-Li alloy. The microstructure, hydrophobic property and corrosion resistance of coatings were investigated by SEM, TEM, XRD, FT-IR, AFM, contact angle tester and electrochemical test. The results indicated that the MgAl LDHs uniformly grown in situ on the NiP coating deposited on Mg-Li alloy through electroless plating and hydrothermal treatment. The MgAl LDHs with a complex honeycomb micro-nano structure improved the surface roughness of the composite coating to 126 nm. The two-step treatment achieved an excellent coupling between the metal-based coating and inorganic compounds. The low surface energy treatment of micro-nano structure on NiP coating surface with stearic acid (@SA) realized the superhydrophobic transition of the composite coating (WAC=154.27° ± 2.56°). Besides, MgAl LDHs showed better trapping properties for Cl-. Under the synergistic effect of anion capture and hydrophobic effect, the corrosion current density (1.35 ×10−7 A⋅cm−2) and impedance modulus of NiP/MgAl [email protected] coating were significantly better than those of NiP and NiP/MgAl LDHs coating. The superhydrophobic composite coating provided a better anticorrosion choice for Mg-Li alloy.