Plasma-polymerized coatings using HMDSO precursor for iron protection

A large microwave plasma reactor was used for the deposition of plasma-polymerized coating from hexamethyldisiloxane (HMDSO)/oxygen (O2) mixtures on iron samples. The plasma was characterized by optical emission spectroscopy as a function of the HMDSO to oxygen ratio. Infrared spectroscopy was used to investigate the coating structure. The variation of the HMDSO content in the feed provides a large wide of coatings, from silica (HMDSO content: 20%) to polymer (HMDSO content >80%). Electrochemical impedance spectroscopy was used to predict corrosion protective properties of the coating. Different HMDSO/O2 ratios in the mixture provide varying degree of corrosion protection and the best protection was obtained for the plasma-polymerized coating from HMDSO 80% content precursor.