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Webinar – Modelling Fe oxide/hydroxide solubility at HTHP Conditions Relevant to Flow-Accelerated Corrosion

Flow-Accelerated Corrosion (FAC) is a well-known source of problems in steam power plants. One of the key factors influencing FAC is the stability of the protective oxide films on the metal surface, which consists mostly of magnetite and/or other forms of iron oxides. Thus, predicting the stability of iron oxides under steam generating conditions is of paramount importance for understanding and predicting conditions related to Flow Accelerated Corrosion.

The stability of iron oxides can be strongly affected by the chemical speciation, particularly those associated with dissolution of iron oxides, hydrolysis of the dissolved iron, oxidation-reduction reactions involving Fe(II) and Fe(III), and complexation of iron species. Any factors influencing chemical speciation will affect the stability of iron oxides, thus, FAC. A rigorous thermodynamic model with a deep understanding of solution chemistry and realistic treatment of speciation are required to predict properties of the corrosive environment and stability of the iron oxides. The technology used to predict thermodynamics of Flow-Accelerated Corrosion is based on the Mixed-Solvent Electrolyte (or MSE) model. This technology allows prediction of both chemical and phase equilibria.

Implemented in the OLI Software, this model predicts the conditions where iron oxides form and/or dissolve, and determines equilibrium chemical speciation, pH, oxidation-reduction potential (ORP) at given temperatures, concentrations of acid, base, chloride, dissolved oxygen or reducing agents. It helps the assessment for effects of different variables on stability and solubilities of iron oxides. Results predicted by the MSE model provide insights to understanding how solubilities of iron oxides change with conditions. This information can guide the client to adjust operation variables to virtually avoid or minimize the flow-induced corrosion.