Self-repairing functionality and corrosion resistance of in-situ Mg-Al LDH film on Al-alloyed AZ31 surface

A novel Mg-Al LDH film was in-situ prepared hydrothermally in an alkaline aqueous solution on an Al-alloyed AZ31 substrate. The structural, chemical and functional characteristics of the film were explored by means of scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS), polarization curve, AC impedance and salt immersion tests, respectively. The anti-corrosion results indicated that the Mg-Al LDH film on the Al-alloyed AZ31 surface could effectively protect the AZ31 from corrosion attack even after 90 days of immersion in 3.5 wt.% NaCl solution. The protection performance is surprisingly better than most of the reported coatings on Mg alloys. More interestingly, when the Mg-Al LDH film was scratched, the exposed Al-alloyed surface might gradually release metal ions and re-generate dense LDH nano-sheets in the corrosive environment to inhibit the further corrosion there, exhibiting a self-repairing behavior. The combination of the benign long-term protection and desirable self-repairing performance in this new process of surface-alloying and LDH-formation may significantly extend the practical application of magnesium alloys. & COPY; 2021 Chongqing University. Publishing services provided by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ) Peer review under responsibility of Chongqing University

Automated summary

A novel Mg-Al LDH film was prepared on an Al-alloyed AZ31 substrate using hydrothermal method. The film's structural, chemical, and functional characteristics were investigated through various tests. The results showed that the Mg-Al LDH film effectively protected the AZ31 from corrosion even after 90 days of immersion in a corrosive solution. Moreover, the scratched film exhibited a self-repairing behavior, releasing metal ions and regenerating dense LDH nano-sheets to inhibit further corrosion.