Aqueous Extracts of Curcuma and Ginger as Green Corrosion Inhibitors on Carbon Steel in Hydrochloric Solution

This research studied the corrosion performance of green corrosion inhibitors (curcuma and ginger) for carbon steel in 1.5M HCl medium. Their inhibition properties was evaluated by several methods, gravimetric and electrochemical tests was employed to determine the inhibition efficiency, corrosion rate and the type of inhibition. The experimentl results show that the inhibition effeciency depends on the change of concentration, at an optimum concentration of 800mg/l, ginger inhibitor reduced corrosion rate to 0.000814 g/cm ² .h, with a 73.46% inhibition efficiency. Curcuma extract at an optimum concentration of 1000mg/l reduced corrosion rate to 0.000331 g/cm ² .h with an inhibitory effeciency of 89.20%, forming a protective hydrophobic film on the metal surface, wich maximally blocked the cathodic corrosive process. Corrosion rate reaches 0.003068 g/cm ² .h without inhibitor. The OCP plot indicates that the potential evolution for the inhibitor free experiment is characterized by a decrease in potential almost − 0.195 V at 200 s,followed by an increase in potential to -0.165 V. These potential changes indicate metal attack followed by anoblissement. In the presence of a ginger inhibitor, the potential increases until it reaches − 0.130 V at 400 s, indicating that the material is accumulating. In the presence of a curcuma inhibitor, the potential decreases until it reaches − 0.191 V, indicating that the metal is being attacked continuously. In addition, the obtained adsorption free energy of-21.024 kJ/mol for curcuma extract and − 19.995 kJ/mol for ginger extract, indicates that the extracts interaction with the metal surface was a physical adsorption, and the adsorption behaviour of extracts was obeyed by Langmuir isotherm .