Preparation and properties of hydrophobic micro-arc oxidation/layered double hydroxide composite coating on magnesium alloy

The rapid degradation rate of Mg alloys limited clinical applications. Layered double hydroxide (LDH) compounds are developed as surface coatings for biomedical magnesium (Mg) alloys. In this work, LDH intercalated with myristic acid ion was in-situ formed on micro-arc oxidized ZK60 alloy using a simple one-step hydrothermal process for controllable and stable degradation. Micro-pores in micro-arc oxidation coating (MAO) were sealed by LDH, and the surface became hydrophobic. With hydrothermal treatment time of 8 h, the MAO/LDH composite coating exhibited the maximum hydrophobicity with a contact angle of about 135.6 degrees and the lowest corrosion current density of about 3.51 x 10-9 A center dot cm- 2. During in-vitro immersion, MAO/LDH composite coating became hydrophilic from hydrophobic, but also provided a good protective ability for Mg alloy. This study provides new insights into the surface modifications of Mg alloys for hydrophobic-hydrophilic transition demand.