An Experimental Study on High Temperature Corrosion of TP347H Stainless Steel in Molten Chloride and Sulfate

The corrosion resistance of TP347H stainless steel was evaluated by measuring mass loss in molten salt at 500-650°C. The corrosion mechanism was characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The results show that the corrosion resistance of TP347H stainless steel increases with the increase of corrosion temperature. When the temperature is below 600°C, TP347H mainly generate low-stable FexOy, and the oxides such as Fe2O3, Fe3O4, Ni1.43Fe1.7O4 and NiFe2O4 are dissolved with the increase of temperature. NbO with higher stability is formed on the surface at 650 °C, which help Cr2O3 and NiO retain for a longer time. Mn-containing compounds on the surface further improve corrosion resistance of TP347H. The corrosion of TP347H stainless steel is mainly intergranular corrosion, and the temperature range of corrosion is consistent with the melting range of alkali metal chloride. Therefore, the molten alkali metal chloride plays a decisive role in the corrosion of TP347H stainless steel.

Ionic Conductivities of Molten Alkali Metal Chloride Binary Systems by Equilibrium Molecular Dynamics Simulation: Composition and Temperature Dependence

Conductivity of molten alkali metal chlorides is the foundation of molten-salt electrolysis process. In the study, equilibrium molecular dynamics was performed to investigate the ionic conductivities of the molten alkali metal chloride binary systems. The calculated values were in good agreement with the experimental results. Simple databases for conductivity have been built based on the verified algorithm. Mathematic expressions of conductivity vs. temperature & composition have also been obtained according to calculated data. Ionic conductivities of these melts exhibited positive dependences on temperature. Adding a smaller alkali metal cation into molten alkali chlorides could improve the conductive performance. With the gradual addition of LiCl, ionic conductivities of molten LiCl-NaCl, LiCl-KCl, LiCl-RbCl, and LiCl-CsCl all increased monotonously. The conductivities of molten NaCl-KCl, NaCl-RbCl, and NaCl-CsCl also increased with the continuous addition of NaCl. The improvement effects of LiCl on ionic conductivities of molten KCl, RbCl, and CsCl are more significant than those of NaCl.

Effect of Additives on Ash Corrosion on Heat Exchanging Surface of Biomass Boilers

This paper focuses on the problems of ash deposition and corrosion caused by alkali metal chloride in biomass boiler. Kaolin, pulverized coal ash, silica fume, dolomite, limestone and bauxite are used as additives in this study, to investigate the degree of corrosion of four metal materials on biomass boiler. The results show that the corrosion rate of metal samples is significantly reduced after adding additives. Kaolin, pulverized coal ash, silica fume and bauxite show much obvious effect on corrosion inhibition. Corrosion resistance of four pipe metals: T91>15CrMoG>12CrMoVG>20G, in which the corrosion resistance of T91 is much better than the other three metals.