Green Technology: Tannin-Based Corrosion Inhibitor for Protection of Mild Steel

For more than four decades, tannins extracted from renewable resources have been used to protect steam boilers at levels significantly above ASME guidelines. Using tanninbased (green) corrosion inhibitors reduces water and energy consumption, greenhouse gases emissions, and contaminants in effluent wastewaters, while reducing the environmental footprint of industrial processes. The surface adsorptive and corrosion protective properties of a commercial tannin-based corrosion inhibitor (TG 3300) for mild steel were investigated in an alkaline environment using quartz crystal microbalance with dissipation monitoring, open circuit potential, and electrochemical impedance spectroscopy (EIS). The results showed the formation of an effective and stable tannin-based protective layer on mild steel within the first 5 min to 15 min of adsorption. It was found that adsorption of TG 3300 on mild steel can be well described by the Langmuir isotherm. Highly negative values of apparent Gibbs free energy of adsorption (Delta G(ads) = -47.36 kJ/mol), indicate a spontaneous and strong adsorption of TG 3300 onto the mild steel surface. The results suggest the formation of a TG 3300 protective layer on mild steel, where the highest value of inhibition efficiency was 85% under the applied experimental conditions.