Molten salt induced corrosion of Inconel 625 superalloy in PbSO4–Pb3O4–PbCl2–Fe2O3–ZnO environment

Corrosion behavior of alloy 625 was studied in a molten salt consisting of 47PbSO4–23 ZnO–13 Pb3O4–10Fe2O3–7PbCl2 (wt.%) under air atmosphere at 600, 700 and 800 °C, utilizing OCP, potentiodynamic polarization, EIS and weight-loss measurement techniques. Phase structure, morphology and chemical analysis of corrosion products and scales were characterized by means of XRD, SEM/EDX, and ICP/AAS.General surface corrosion, intergranular corrosion, formation of voids and, a network of distributed pores on surface and cross-section, plus internal oxidation and sulfidation were identified as different modes of corrosion attack. EIS data fit to a porous and non-protective barrier layer electrochemical model.

► Alloy 625 presented active dissolution behavior. ► Anodic film was characterized as a porous, non-protective corrosion product layer. ► General and intergranular corrosion together with voids and pores formation occurred. ► Internal oxidation and sulfidation were different modes of hot corrosion attack. ► EIS data fit to a porous and non-protective barrier layer electrochemical model.