Corrosion Behavior of Silicon-Bearing Steel in a Wet/Dry Environment Containing Chloride Ions

Abstract

The rust of Si-bearing steel was analyzed by EPMA, XRF, XPS and TEM, and the electrochemical behavior of the rusted steel was investigated by the electrochemical impedance spectroscopy (EIS) method after wet/dry cyclic corrosion test with chloride ions. The 2.0 mass% Si-bearing steel showed high corrosion resistance compared to carbon steel (SM) in the corrosion test. EPMA and XPS showed that Si existed as a intermediate oxidized state such as Si 2+ in the inner rust layer for Si-bearing steel. TEM showed that nano-scale complex oxides containing Si were formed in the inner rust of the Si-bearing steel. EIS measurement was taken to estimate the rust resistance (Rrust) and corrosion reaction one (Rt) of the rusted steel. It was found that Rrust and Rt of Si-bearing steel were much larger than those of SM after the rust formation. The corrosion of Si-bearing steel could be suppressed by the formation of the nano-scale complex oxide containing Si in inner rust layer to prevent the penetration of Cl ions.