Author: Eng. Amir Anwer Elsayed Osman
The oil and gas industry faces a significant challenge in preventing corrosion of petroleum above ground storage tanks (AST). Leaks from failed tanks pose a significant environmental threat and have business interruption impacts. To address this issue, a study was conducted on carbon steel plates (A283 Gr. C) and corrosive solutions from bottom water samples that were withdrawn from petroleum storage tanks (FB-101 and FB-2250) at the Alexandria Mineral Oils Company (AMOC) site. Electrochemical techniques such as electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) were applied to study corrosion and confirm the inhibitor's results, as well as weight loss measurements. The study found that sodium alginate inhibitor effectively inhibited carbon steel in the bottom waters of tanks FB-2250 and FB-101, with inhibition efficiencies of 79.4% and 75.8% at 30 degrees Celsius, respectively, and inhibition efficiencies decreasing as the temperature increased. The results were highly proportional to the Langmuir isotherm adsorption model, and thermodynamic calculations indicated that the activation energy increased in the presence of an inhibitor. The Gibbs free energy value was also less than 20 kJ/mol, indicating physical adsorption on the metal surface. The enthalpy and entropy values were indicating spontaneous adsorption and more order.