Optimization of cold plasma process parameters for organosilicon films deposition on carbon steel: Study of the surface pretreatment effect on corrosion protection performance in 3 wt% NaCl medium

Organosilicon films were deposited on carbon steel using plasma enhanced chemical vapour deposition (PECVD) process prepared from cold plasma polymerization of 1,1,3,3-tetramethyldisiloxane (TMDSO). The experimental design technique allowed determining the optimal conditions of the plasma process. The effect of different surface pretreatments was investigated using amorphous phosphatation, argon (Ar) and nitrogen (N2) plasma. Coatings showing a hydrophobic character and good adhesion were obtained. Several surface characterization techniques using Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), contact angle, cross-cut and surface profilometry were used. The protection efficiency against corrosion of the deposited films has been demonstrated by coupling different electrochemical techniques such as open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) in 3 wt% NaCl solution. The organosilicon coatings showed good barrier against corrosion even after long immersion time in the aggressive environment, especially when N2 plasma pretreatment is performed.