Calcium titanate corrosion inhibitor enabling carbon as inert anode for oxygen evolution in molten chlorides

Abstract

The corrosion inhibition efficacy of titanate (CaTiO₃) for carbon anodes in molten salts was investigated through various analytical techniques, including linear sweep voltammetry, X-ray diffraction, scanning electron microscopy, and energy dispersion spectroscopy. The results demonstrate that the addition of CaTiO₃ corrosion inhibitor efficiently passivates the carbon anode and leads to the formation of a dense CaTiO₃ layer during the electrolysis process in molten CaCl₂−CaO. Subsequently, the passivated carbon anode effectively undergoes the oxygen evolution reaction, with an optimal current density for passivation identified at 400 mA/cm². Comprehensive investigations, including CaTiO₃ solubility tests in molten CaCl₂−CaO and numerical modeling of the stability of complex ionic structures, provide compelling evidence supporting “complexation−precipitation” passivation mechanism. This mechanism involves the initial formation of a complex containing TiO₂·nCaO by CaTiO₃ and CaO, which subsequently decomposes to yield CaTiO₃, firmly coating the surface of the carbon anode. In practical applications, the integration of CaTiO₃ corrosion inhibitor with the carbon anode leads to the successful preparation of the FeCoNiCrMn high-entropy alloy without carbon contamination in the molten CaCl₂−CaO.