Advances in LDHs for corrosion-resistant protection of Mg and Al alloys: A review

Layered double hydroxides (LDHs) as coatings attract much attention in corrosion and protection of light metals due to their interesting properties such as in-situ synthesis, unique layer-stacking structure, tunable composition, and good biocompatibility as well. Currently, single LDH coating faces challenges such as time-consumed synthesis, thin coating thickness and inadequate density. This paper provides a systematic review of the cutting-edge advancements in modulation of composition, synthesis and applications of LDHs on Mg and Al alloys in corrosion protection and biomedical fields. The focus is concentrated on the intercalation of corrosion inhibitors into LDH coatings. Particularly the anti-corrosion mechanisms of both inorganic anions (nitrate, vanadate, and molybdate) and organic anion intercalation (carboxylic acid anions and hydroxyquinolines) were discussed within the context of corrosion inhibitor intercalation LDH. The modification of LDHs is introduced with low surface energy substances such as silanes and fatty acids. The formation mechanism of LDH films and the active anti-corrosion mechanisms were proposed. A comparison of LDH coatings between Mg alloy and Al alloy was carried out from different perspectives, and further researches on LDH corrosion protection were prospected.