Synergistic mechanism of ASP on growth and corrosion protection of Mg-Al-Ca-LDH film on Mg-Li alloy

The Mg-Al-Ca-LDH film was prepared on Mg-Li alloy by means of the in-situ hydrothermal method, with aspartic acid (ASP) acting both as a growth regulator and a corrosion inhibitor. The microstructure of the film was characterized by means of SEM, EDS, XRD and FT-IR. The corrosion resistance of the samples was evaluated using electrochemical impedance spectroscopy and a hydrogen evolution test. The results demonstrated that: at a concentration of 0.1 M aspartic acid, the film exhibits a needle-like structure. The charge transfer resistance of the film is measured at 926.9 ohm·cm 2 . This value is two orders of magnitude higher than that of the substrate and higher than that of Mg-Al-Ca LDH film. Furthermore, the self-corrosion current density of the film is the lowest in comparison with other concentration films. Following an immersion period of 216 h, the presence of the LDH peak on the (003) crystal plane, both prior to and following corrosion. It indicates the persistence of a substantial film layer on the surface. Aspartic acid has been demonstrated to facilitate the self-healing of metal matrix through the regulation of the orientation of LDH nanosheets within the film, ion exchange with Cl − in the etching solution and the promotion of recrystallization of cations released from the damaged film.