Investigation of the corrosion behaviour of steel coated with amorphous silicon carbon alloys

Thin amorphous silicon (a-Si:H) and carbonated silicon (a-Si_1-xC_x:H) layers were deposited on stainless steel substrates using plasma-enhanced chemical vapour deposition (PECVD) in a "low-power" regime. The carbon content of the carbonated silicon (a-Si_1-xC_x:H) alloys was varied between 0.1 and 0.37at.%. The performance of these interfaces as effective corrosion barriers in 3% sodium chloride aqueous solutions was evaluated. Potentiodynamic polarisation curves and electrochemical impedance spectroscopy (EIS) were used next to X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) to investigate the protection efficiency of the different barriers. The a-Si:H coated showed better corrosion resistance as compared to the carbonated silicon alloys. No degradation was observed after 14days immersion of the steel substrate coated with a-Si:H in 3% sodium chloride aqueous solution, making this coating an attractive candidate as corrosion barrier.