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A first principle mathematical model of the formation of calcareous deposits on a cathodically protected steel rotating disk electrode in seawater is presented. The model includes equations which transport phenomena, electrochemical reac-tions, precipitation reactions, and a homogeneous reaction involved in the formation of calcareous deposits on an electrode surface. Predicted concentration profiles show that a high concentration of OH- ions on the electrode surface leads to the formation of calcareous deposits. The calcareous deposits contain mostly CaCO3, but the initial deposits are predicted to contain more Mg(OH)2 than CaCO3. The predicted calcareous deposits on the electrode surface reduce the active surface area available for the electrochemical reactions, which results in a decrease in the cathodic urrent density. The predicted current density as a function of time during the formation of deposits agrees qualitatively with experimental data. The main electrochemical reactions that occur during the corrosion of steel structures in seawater are the oxidation of iron Fe--- Fe =+ 2e- 1 the reduction of oxygen 02 + 2H20 + 4e--- 4 OH- 2 and hydrogen evolution
Yan et al. (Mon,) studied this question.