Anodic corrosion of iridium in the LiCl + KCl eutectic melt

• Published in: Journal of electroanalytical chemistry and interfacial electrochemistry 1990-09, Vol.290 (1), p.105-118
• Main Authors: Colom, F., de la Plaza, A.
• Format: Article
• Language: English
• Subjects: Applied sciences; Corrosion; Corrosion environments; Exact sciences and technology; Metals. Metallurgy
• ISSN: 0022-0728
• DOI: 10.1016/0022-0728(90)87423-H

The anodic behaviour of Ir in fused KCl + LiCl eutectic between 400 and 600°C has been studied by cyclic voltammetry. The potential sweep shows a metal dissolution current and passivation peak whose current density and potential depend on the potential scan rate and temperature. At high positive potentials chlorine evolution is observed. At 400 ° C no metal attack is detected unless the electrode has been previously corroded. Passivation is attributed to precipitation of supersaturated alkali-iridium chlorides on the electrode, although the formation of a porous IrO 2 layer is also observed. Analytical determination of the Ir corrosion products as a function of the electrode potential at 500°C reveals that the metal goes into the melt as IrCl 6 3+ with 100% current efficiency at potentials before passivation. In the passivation region, the current yield decreases and a mixture of IrCl 6 3− and IrCl 6 2− is obtained. At trans-passivation and chlorine evolution potentials a small electrode corrosion rate is measured with the formation of IrCl 6 2−.