Multifunctional coating on magnesium alloy: Superhydrophobic, self-healing, anti-corrosion and wear-resistant

Superhydrophobic coating (SHC) was fabricated on magnesium (Mg) alloy by sequential surface etching, in-situ growth of MgAl-layered double hydroxides (LDHs), and modification of octadecyl-trimethoxy-silane (OTMS). The so-fabricated SHC possessed high contact angle above 150° and low sliding angle below 10° by using the probe droplet of aqueous solution of HCl (pH = 2), NaOH (pH = 13), NaCl (3.5 wt.%) or others such as milk, cola, and tea. The lubricant behavior as well as wear resistance was enhanced by such a SHC as compared with the bare Mg alloy. Moreover, corrosion of Mg alloy was greatly slowed by such a SHC which maintained long-term hydrophobic property after corrosion immersion in aqueous solution of NaCl for 6 weeks. The scratch on the SHC could be self-healed by immersing into water due to the hydrolytic polycondensation of silane and corrosion decomposition of LDHs within 8 days.