The corrosion of potlining refractories: A unified approach

The study of corrosion chemistry of aluminosilicate refractories in potlinings has historically focused on a single corrosive agent: either molten sodium fluoride or metallic sodium. Each approach can explain only a fraction of in-field observations. This article presents a unified approach, taking into account the effect of both corrosion agents on aluminosilicates. Along with the model, mathematical tools have been developed to help interpret experimental results as well as to make predictions of in-service behaviors. Those predictions are based on the use of corrosion maps, which vary according to the sodium ratio R_Na=N_Na(M)/(N_NaF+N_Na(M))], as well as other parameters. Predictions made with the model match almost perfectly with the results obtained in a wide range of corrosion conditions. Depending on the quantity of fluorides that a lining lets percolate and the amount of metallic sodium diffusing, cells can be divided into two distinct groups: wet or dry. This article discusses the wet/dry distinction, including industrial aspects. For more information, contact C. Allaire, CIREP-école Polytechnique, 8475 Christophe-Colomb, Montréal, Québec, Canada, H2M 2N9; e-mail claude.allaire@courriel.polymtl.ca.