Preparation of Superhydrophobic Coating and Its Corrosion Resistance to Mg-Li Alloy

In this paper, superhydrophobic nano silica coating applied for improving anticorrosion properties of Mg-Li alloy with high chemical activities was prepared by sol-gel method with tetraethylorthosilicate (TEOS) as the resource of silica, and modified with vinyltrimethoxysilane (VTMS) in further. Chemical structures of silica and modified silica were evaluated by FTIR. Surface morphologies of superhydrophobic coating with different ammonia amount were observed by scanning electron microscopy (SEM). Hydrophobic properties of superhydrophobic silica coatings were tested by contact angle (CA), and anticorrosion properties of superhydrophobic silica coatings were tested by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. Chemical component change of Mg-Li alloy surface was evaluated by XPS. The results indicate that the superhydrophobic surface expresses good roughness when the ratio of ammonia and TEOS is 1 : 1 for superhydrophobic silica coatings, the contact angle reached 151 degrees, and slide angle is only 5 degrees. The superhydrophobic nano silica coating is greatly improved corrosion resistance ability of Mg-Li alloy, whose electrochemical impedance is high up to 10(5) Omega, and corrosion current density is merely 6. 19x10(-8) A/cm(2).