Effect Of So42- And Hco3- To The Electrochemical Protection Of Fes1-X Scale To P110 Steel

The electrochemical protection of FeS1-x scale to the P110 steel in two different solutions were researched by designed experiments including Mott-Schotty, potentiodynamic polarization, electrochemical impedance spectroscopy and weight loss. To understand some aspects of the mechanism, XRD, XPS and SEM were also adapted. FeS1-x scale in 0.5 mol/L Na2SO4 solution presented lower protection to the steel, because the electron transfer and mass diffusion in the scale were easy. After immersion, the Fe/S atomic ratio of scale decreased, which resulted in increasing cation vacancy. As a result, p-type semiconducting property was found. However, the electron transfer and mass diffusion in the scale were mitigated in NaHCO3 solution, so the electrochemical protection to the steel was enhanced. On the contrary, the Fe/S atomic ratio of scale changed little. High anodic polarization resistance inhibited diffusion of Fe2+. Fe2+ became interstitial cation by this way. The n-type semiconducting property, thus, was observed.