Advances in LDH coatings on Mg alloys for biomedical applications: A corrosion perspective

The clinical applications of biodegradable magnesium (Mg) alloys for implant applications have yet to be successfully applied, in part due to their rapid corrosion following the initial implant period in the physiological environment. Surface modifications for Mg alloys remains the most appropriate strategy to overcome the rapid corrosion rate and to improve the biomedical performance of Mg alloys. Although surface modifications have been extensively researched, limitations of current surface modification approaches are still present. Thus, layered double hydroxide (LDH) films have gained much attention as a potential approach since the films are able to delay the corrosion during the initial phase of implant of Mg alloys owing to their tunable crystal structure, ability to trap corrosive anions and intercalation with various anionic-based corrosion inhibitors. Furthermore, the biodegradability and biocompatibility of LDH films make them a potential next generation coating for implant applications. This review details the recent development of LDH and its composite coatings on Mg alloys as a potential protective coating for implant applications. The synthesis parameters affecting the structural and morphological properties of LDH films are discussed. The state-of-the-art of LDH and its composite coatings for corrosion mitigation are also assessed. Finally, this review concludes with the standing challenges, limitations, and future directions of LDH as a multi-functional coating on Mg alloys for biodegradable implant applications.