Hydrothermally prepared layered double hydroxide coatings for corrosion protection of Mg alloys – a critical review

•State-of-art progress of hydrothermally prepared LHD coatings upon Mg alloys was critically reviewed.•Roles of processing variables in hydrothermal preparation of LDH coatings on Mg alloys were articulated.•Limitations and research gaps of existing LDH coatings were discussed.•Research directions were proposed to prepare robust LDH coatings for tackling corrosion challenges of Mg alloys.