Investigation on hydrophobic films from a hydrophobic powder

A hydrophobic powder was prepared based mainly on an organosiloxane and a corrosion inhibitor with the addition of a reaction promoter. Structure and thermal stability of the hydrophobic powder were characterized by FTIR and TG/DSC, respectively. Hydrophobic property and corrosion resistance of the hydrophobic film formed on phosphatized steel by immersion in 3 wt% NaCl aqueous solution were evaluated together with the electrochemical behavior. Results showed that the skeleton of the hydrophobic powder was composed mainly of -Si-O-Si which comprises longer and more hydrophobic groups of -Si-R compared with the conventional BH-102 water-repellent agent. A thin hydrophobic film with a thickness of 15-20 mu m was formed on surface of the phosphatized steel after immersion in the solution of 5 g/L of the hydrophobic powder in ethanol for 5 min. The hydrophobic film exhibited excellent stability at a temperature below 135 degrees C. Water contact angle on the film is about 117-132 degrees and it was until 30 h later when a corrosion spot occurred on the film covered on steel which revealed better water-repellent and corrosion resistant properties compared to that of the BH-102. (C) 2012 Elsevier B. V. All rights reserved.