Electrochemical study of the corrosion of a Ni-based alloy GH3535 in molten (Li,Na,K)F at 700 degrees C

The compatibility of structural materials with molten fluoride salts is an immediate challenge for the application and development of molten salt reactor (MSR) operating at high temperatures. In the present presentation, the corrosion behavior of a nickel-based alloy GH3535 has been examined in an eutectic (Li,Na,K)F melt at 700 degrees C under Ar and Ar-5%H2O, respectively, by some electrochemical techniques. Moreover, the effect of the additive CrF3 with concentrations of 0.09 and 0.18 M on the corrosion of the alloy in the melt has also been investigated in an attempt to understand the corrosion mechanism involving the multivalent transition metal Cr ions Cr2+/Cr3+. It is shown that the alloy is in active dissolution state at the corrosion potential and its corrosion occurs mainly through the preferential dissolution of Cr from the substrate, producing a Cr-depleted layer and some internal voids. The introduction of 5%H2O in Ar accelerates obviously the corrosion of the alloy, giving rise to the formation of a wider Cr-depleted layer where some Cr-rich internal oxides are formed over the internal voids. CrF3 itself acts as an oxidizer to accelerate the dissolution of Cr, with a more significant effectiveness observed for a higher CrF3 content. (C) 2015 Elsevier B.V. All rights reserved.