Kinetics and mechanisms of corrosion in magnesia–carbon refractories by chromium-oxide-containing calcium aluminate slag

The effect of the Cr₂O₃ content of a synthetic CaO–Al₂O₃–SiO₂–MgO base slag on MgO–C refractory corrosion was studied using controlled lab-scale experiments and thermodynamic modeling. A synthetic slag was designed to replicate a ladle furnace slag exhibiting high desulfurization capacity. The base slag was saturated with MgO to eliminate the thermodynamic driving force for MgO dissolution and to isolate the effect of Cr₂O₃ on slag penetration and refractory corrosion. Corrosion experiments were conducted at 1625 °C in a horizontal tube furnace in an Ar atmosphere, with slags containing 0, 5.0, and 10.0 wt% Cr₂O₃ for exposure times of 30, 60, and 90 min. Microstructural characterization using scanning electron microscopy coupled with energy dispersive spectroscopy revealed that increasing Cr₂O₃ content increased slag penetration depth and accelerated corrosion kinetics, primarily through the decarburization of Cr₂O₃ by reaction with the carbon matrix of the refractory and the dissolution of MgO. Effective penetration rate coefficients were determined for each slag composition, confirming the strong correlation between slag Cr₂O₃ content and refractory degradation. These findings provide mechanistic insights into the role of Cr₂O₃ in slag–refractory interactions and are directly relevant to stainless steelmaking and high-chromium alloy production, where Cr₂O₃-containing slags are prevalent and refractory performance is critical to process efficiency and lining life.