Electrochemical impedance spectroscopy (EIS) studies of the corrosion of pure Fe and Cr at 600 °C under solid NaCl deposit in water vapor

Abstract

The corrosion behavior of pure Fe and pure Cr at 600 °C under a deposit of solid NaCl, with and without the presence of water vapor, was studied by using electrochemical impedance spectroscopy (EIS) and mass gain measurements. The mass gain of both metals sharply increased when water vapor was introduced into the system. In EIS measurement, only one capacitive loop obtained on the pure Fe and Cr coated with solid NaCl and gave the information of oxide layer on them. For the oxide in air, there is a good relationship between the R ox and the reaction rate for both pure Fe and Cr with different oxide time. The lower the R ox is, the higher the reaction rate is. Although no good relationship can be set up between the R ox and the reaction rate when water vapor presented, its trend with oxide time for both metals is generally in accordance with that of the corrosion rate measured by the mass gain curves. The electrochemical technique is an effective method for studying corrosion performance at high temperature.