Corrosion performance of carbide/nitride/oxide (C/N/O)-based reactor during thermochemical hydrogen production by Na redox reaction

Abstract

The corrosion of carbide/nitride/oxide(C/N/O)-based reactor materials were investigated to solve the corrosion problems in sodium redox reactions for thermochemical hydrogen production in this work. Various types of carbides, nitrides, and oxides were used as the potential materials of reaction containers for the sodium redox cycle to expect strong corrosion resistance. Comparison of corrosion of materials was performed by heat treatment with Na2O at 500 °C and corrosive phases were identified by X-ray diffraction. All the carbides materials showed the low corrosion resistance, while AlN among all the nitrides and Al2O3 among all the oxides were proved to possess high corrosion resistance with a very less corrosive phase from XRD results and non-discoloration of the test plate. The order of corrosion resistance of various materials was determined from the width of the corrosive layer observed by SEM and from the evaluation of Gibbs energy corresponding to the corrosion reaction from the thermodynamic point of view. The order of corrosion resistance was found to be AlN > Al2O3> ZrO2> TiO2. As a result, AlN was the most corrosive-resistant material according to SEM, XRD and EDS methods.