PLASMA POWER IMPACT ON ELECTROCHEMICAL PERFORMANCE OF LOW CARBON STEEL COATED BY PLASMA THIN TEOS FILMS

Abstract

Electrochemical properties of thin silicon oxy carbide films were investigated as anticorrosive coatings. The film was deposited on low carbon steel substrate by radio frequency capacitive coupled plasma technique using tetraethyl ortho silicate (TEOS) as a precursor and Ar was used as a carrier gas in dependence on the applied power. The chemical composition and morphological of the deposited films were examined by energy-dispersive X-ray spectroscopy (EDX) coupled with scanning electron microscopy (SEM). The SEM results confirm a pinhole-free layer of oxy carbide was formed on the steel surface after plasma treatment. The corrosion resistance of the coatings was analyzed by potentiodynamic polarization and electrochemical spectroscopy (EIS) in 3.5% NaCl solution at room temperature. The electrochemical results show remarkable corrosion resistance enhancement after plasma treatments. The corrosion current (icorr) is significantly reduced from 12 µA/cm2 for the blank sample to 1 and 0.3 µA/cm2 for treated samples at 50, and 100 W, respectively. A marked increase of the protective properties was detected by 100 W sample with protective efficiency more than 98 % at room temperature.