In-situ formation of self-assembled hydrophobic Mg(OH)₂/organosilane composite coatings under the driven of quadruple hydrogen bonds with enhanced corrosion properties

The close density, elastic modulus of magnesium and magnesium alloys to those of human bone, as well as their good biodegradable and bio-safety make them attractive as biomaterials. However, rapid degradation rate seriously limits their applications. In this study, an organic silanes (TES) containing quadruplet hydrogen bond structure was synthesized. In-situ formation of self-assembled Mg(OH)₂ coating was prepared at first on pure magnesium surface by one-step hydrothermal method. And then self-assembled organosilane coatings was fabricated under the motivation of quadruple hydrogen bonding on Mg(OH)₂ coating by sol-gel dip-coating. The dense cage-liked braided structure of Mg(OH)₂ coating promotes the good bonding between the organosilane and Mg(OH)₂ coatings. The contact angle of the sample with Mg(OH)₂ coating is about 20.50°. The surface changes from hydrophilic to hydrophobic after the organosilane coating treatment. The contact angle increases to 113.99° and 135.49° with one and three passes dip-coating, correspondingly. The complete and dense hydrophobic composite coating could provide effectively barrier effect and improve the corrosion resistance of pure magnesium. After 3 times organosilane coating, the Mg(OH)₂/organosilane composite coating shows the minimum corrosion tendency with the most positive corrosion potential (−1.27 V) and the lowest corrosion currency (1.50 ×10⁻⁴A·cm⁻²) in the simulated body fluids.