Galvanic Corrosion in Molten Salts: A Discussion of the Corrosion Mechanism of Two-Phase Ni–20Cr–20/30Cu Alloys in Eutectic (Li,K)2CO3 at 650°C

Abstract

The corrosion of a Ni-20Cr and three ternary Ni-20Cr-Cu alloys containing 10, 20 and 30 wt.% Cu, respectively, in a eutectic (Li, K) 2 CO 3 melt was studied at 650 • C under air.

Composite Cu-LaFeO3Conversion Coatings on a 18Cr Ferritic Stainless Steel for IT-SOFC Interconnects: An Investigation on Structure and Formation Mechanism

“…An interesting work has been recently made by Zeng et al, who report an example of galvanic corrosion observed on a multi-phase Ni/Cu alloy in a eutectic (Li,K) binary carbonate at 650 • C. Galvanic corrosion resulted in an accelerated corrosion of the less noble phase and deposition of a Ni/Cu metallic phase. 35 Galvanic coupling is likely to occur also in the present molten carbonate system, since copper is a much more noble element than nickel, chromium or iron. [35][36][37] Therefore, the addition of copper to the melt could promote the oxidation of less noble steel alloying elements, in particular iron and chromium, resulting in the galvanic reduction and deposition of metallic copper.…”

“…35 Galvanic coupling is likely to occur also in the present molten carbonate system, since copper is a much more noble element than nickel, chromium or iron. [35][36][37] Therefore, the addition of copper to the melt could promote the oxidation of less noble steel alloying elements, in particular iron and chromium, resulting in the galvanic reduction and deposition of metallic copper. The presence of a galvanic contact may explain the accelerating effect of copper additions on the conversion coating process similarly to what is a well assessed practice in the phosphate conversion process.…”