Abstract Scope |
Dealloying of electrochemically reactive elements (e.g., Cr, Fe) is the dominant and detrimental form of corrosion in high temperature molten salts. This work studies alloying effects by use of Fe-(Cr)-Ni model alloys in model molten chloride salts at different homologous temperatures. We have developed a reliable Mg|Mg2+ reference electrode for these media, including in-situ electrochemical measurement of residual impurity content. We have discovered that at low homologous temperature, a microporous Ni layer evolves, and the dealloying mechanism is controlled by surface diffusion of more-noble element; compared with aqueous systems, the parting limit (55-60 at.% of less-noble element) is reduced by several percent due to increased surface mobility of Ni in molten Cl salts. We will also talk about changing criteria for dealloying at high homologous temperature where the operative mass transport is mediated by vacancy diffusion, porosity changes its appearance to negative dendrites, and the parting limit becomes meaningless. |