Effect of SO₄2- and HCO₃- to the Electrochemical Protection of FeS_1-x Scale to P110 Steel

摘要

The electrochemical protection of FeS1-x scale to the P110 steel in two different solutions wereresearched by designed experiments including Mott-Schotty, potentiodynamic polarization,electrochemical impedance spectroscopy and weight loss. To understand some aspects of themechanism, XRD, XPS and SEM were also adapted. FeS1-x scale in 0.5 mol/L Na2SO4 solutionpresented lower protection to the steel, because the electron transfer and mass diffusion in the scalewere easy. After immersion, the Fe/S atomic ratio of scale decreased, which resulted in increasingcation vacancy. As a result, p-type semiconducting property was found. However, the electron transferand mass diffusion in the scale were mitigated in NaHCO3 solution, so the electrochemical protectionto the steel was enhanced. On the contrary, the Fe/S atomic ratio of scale changed little. High anodic2+ 2+ polarization resistance inhibited diffusion of Fe . Fe became interstitial cation by this way. The n- type semiconducting property, thus, was observed.