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Electrochemical studies of Inconel alloys 617 and 625 in molten PbCl2 : KCl mixture Golozar, Maryam


Behavior of Inconel alloys 617 and 625 in PbCl₂ -KCl molten salt system at three temperatures of 450, 550, and 650°C in air atmosphere and air-15%CO₂ atmosphere were compared using different electrochemical experiments. Electrochemical experiments performed included open circuit potential, potentiodynamic polarization, linear polarization, and electrochemical impedance spectroscopy in order to examine the in situ electrochemical behavior of these alloys at high operating temperatures. In addition, Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDX) were used to examine the cross section of the alloy and characterize chemical composition of the oxide at different temperatures after exposure to molten salt. To obtain phases of the scale formed on the surface of alloys, X-ray diffraction (XRD) was also used. At all temperatures, corrosion resistance for alloy 625 was greater than alloy 617, thus, the corrosion rate for alloy 617 was slightly more than alloy 625. With increasing temperature, the corrosion rate increased. Both alloys formed a Cr₂O₃ scale. This scale became porous and, as a result, corrosion spices penetrated through the pores. This diffusion of corrosive species was the root cause for corrosion in the two alloys. Other alloying elements that formed oxides and chlorides included Cr, Ni, Mo, Co, and Nb.

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