Room temperature synthesis of water repellent silica coatings by the dip coat technique

The present paper describes the room temperature synthesis of dip coated water repellent silica coatings onto stainless steel substrates using 1,1,1,3,3,3-hexamethyldisilazane as a surface modifying agent. The hydrophobic property of the silica coating was enhanced by increasing its surface roughness, which was achieved by a proper control over the MeOH/TMOS molar ratio (S) during the synthesis. The contact angle of a water droplet (10 mu l) increased from 72 degrees to 145 degrees with an increase in the S value from 9.1 to 36.4. The silica coating showed a minimum sliding angle of 15 degrees for a water droplet of 10 mu l. The water repellent silica coatings are thermally stable up to a temperature of 340 degrees C. The results have been discussed by taking into consideration the contact angle measurements, surface morphology and sol-gel parameters. (c) 2006 Elsevier B.V. All rights reserved.