Investigating corrosion behavior of Ni and Ni-20Cr in molten ZnCl2

Polarization curves and corresponding schematic representation of corrosion mechanism for Ni and Ni-20Cr in molten ZnCl2 at 593 K. [Display omitted] •Ni and Ni-20Cr corrosion in molten ZnCl2 at 593 K was reported for the first time.•Ni and Ni-20Cr specimens after corrosion testing were characterized with SEM, HRTEM/STEM, and EDS.•Polarization studies showed that the corrosion rate for Ni-20Cr is 3 orders of magnitude higher than Ni.•Grain boundary attack and subsequent pore-salt network formation were observed in Ni and Ni-20Cr.•Ni-20Cr exhibited anodic dissolution of Cr and resultant CrClx film formation at the metal/salt interface. Corrosion of Ni and Ni-20Cr in molten ZnCl2 under argon atmosphere at 593 K was investigated using cyclic polarization in combination with various electron microscopy techniques. Cyclic polarization measurements yielded significantly lower corrosion rates for pure Ni than for Ni-20Cr. Corrosion of the Ni-20Cr alloy is attributed to selective anodic dissolution of Cr, which forms a chromium chloride film at the metal-salt interface. The corrosion in Ni and Ni-20Cr is accelerated by grain boundary attack through intergranular corrosion, followed by the formation of pore-salt network regions. The related corrosion mechanisms and dissolution kinetics are discussed.