Synthesis of plasma-polymerized hexamethyldisiloxane (HMDSO) films by microwave discharge

The microwave-plasma assisted deposition of hexamethyldisiloxane [HMDSO-(CH3)(3)SiOSi(CH3)(3)] plasma polymer (PP) films for corrosion protection of Al sheet metal surfaces was investigated. Ar, O-2 and H-2 carrier gases at flow rates up to 150 sccm and microwave power densities up to 5 W/cm(2) were used. The process pressure was varied between 1.5 and 3.7 mbar. A mass spectrometer was used to monitor the exhaust gas composition and the monomer decomposition. FTIR and XPS measurements were used to characterize the highly cross-linked PP-HMDSO layers. The deposited films exhibited corrosion protection properties similar to those observed for specially prepared evaporated Al films with a chemical resistance to a 1.0 mol/l NaOH solution. Also, the adhesion of the coating to the substrate was good. The polymer layers (thickness similar to 1 mu m) were found to be quite chemically homogenous. Static contact angles <35 degrees measured with respect to water characterize the wetting properties. (C) 1998 Elsevier Science S.A.