Hydrophobic Silica Coating Based on Waterglass on Copper by Electrophoretic Deposition

Abstract

Hydrophobic silica coating on copper (Cu) has been successfully prepared byelectrophoretic deposition (EPD) of silica sol prepared from waterglass. trimethyl chlorosilane (TMCS) was used as the modifying agent to produce hydrophobic coating by replacing the silanol groups on the silica surface with alkyl groups. The hydrophobicity was indicated by the contact angle of water droplet on the coating surface. It has been shown that TMCS concentration plays an important role in the preparation of hydrophobic coating. However, higher concentration of TMCS made the copper corroded before coated with silica due to the production of Cl-ions when TMCS reacted with water and silanol groups during electrophoretic deposition. In addition, the electricfield intensity, silica concentration and deposition time also influence the hydrophobicity of the coating. Increasing the three parameters produces silica coating with higher hydrophobicity. Thecontact angle of the silica coating can reach 130°. EIS analysis showed that the silica coating is very porous.