High Temperature Materials and Processes · 2020 · 54 citations · 19 references
Natural SciencesMaterials EngineeringMaterials ScienceCorrosion ScienceElectrochemistryMetallic MaterialsCorrosion EngineeringCorrosion KineticsCorrosion MechanismsCorrosion ResistanceCorrosion TestingElectrochemical CorrosionActive CorrosionCharge Transfer ResistanceCorrosion ProductsElectrochemical Corrosion TestingElectrochemical Impedance AnalysisMolten Salt CorrosionPotentiodynamic PolarizationTemperature Dependence Of Corrosion Rates
Abstract Corrosion behaviors of 316 stainless steel (316 ss) and Inconel 625 alloy in molten NaCl–KCl–ZnCl 2 at 700°C and 900°C were investigated by immersion tests and electrochemical methods, including potentiodynamic polarization and electrochemical impedance spectroscopy. X-ray diffraction and scanning electron microscopy/energy dispersive spectroscopy were used to analyze the phases and microstructures of the corrosion products. Inconel 625 alloy and 316 ss exhibited high corrosion rates in molten chlorides, and the corrosion rates of these two alloys accelerated when the temperature increased from 700°C to 900°C. The results of the electrochemical tests showed that both alloys exhibited active corrosion in chloride molten salt, and the current density of 316 ss in chloride molten salt at 700°C was 2.756 mA/cm −2 , which is about three times the value for Inconel 625 alloy; and the values of the charge transfer resistance ( R t ) for Inconel 625 were larger than those for 316 ss. The corrosion of these two alloys is owing to the preferred oxidation of Cr in chloride molten salt, and the corrosion layer was mainly ZnCr 2 O 4 which was loose and porous and showed poor adherence to metal.
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