The Corrosion Behavior of Pure Iron under Solid Na(2)SO(4) Deposit in Wet Oxygen Flow at 500 °C

The corrosion behavior of pure Fe under a Na(2)SO(4) deposit in an atmosphere of O(2) + H(2)O was investigated at 500 °C by thermo gravimetric, and electrochemical measurements, viz. potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and surface characterization methods viz. X-ray diffraction (XRD), and scanning electron microscope (SEM)/energy dispersive spectroscopy(EDS). The results showed that a synergistic effect occurred between Na(2)SO(4) and O(2) + H(2)O, which significantly accelerated the corrosion rate of the pure Fe. Briefly, NaFeO(2) was formed in addition to the customary Fe oxides; at the same time, H(2)SO(4) gas was produced by introduction of water vapor. Subsequently, an electrochemical corrosion reaction occurred due to the existence of Na(2)SO(4), NaFeO(2), and H(2)O. When this coupled to the chemical corrosion reaction, the progress of the chemical corrosion reaction was promoted and eventually resulted in the acceleration of the corrosion of the pure Fe.