Enhancing the corrosion inhibition performance of Tinospora cordifolia extract using different fractions of methanol solvent on carbon steel corrosion in a seawater-simulated solution

The present study investigates the inhibition potential of Tinospora cordifolia extract in combination with different methanol solvents on the corrosion of carbon steel in artificial seawater environments. Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) methods were utilized to evaluate this inhibitor. The measurement data show a positive correlation among inhibition efficiency (%IE), inhibitor concentration, temperature, and time. However, above 320 K, the efficiency has a slight decline, as well as when the exposure duration extends beyond 30 minutes. The highest observed inhibition efficiency was 85.94%, achieved by incorporating 300 mgL-1 of T. cordifolia extract (at 310 K). The inhibition by T. cordifolia extract was sugested to occur through adsorption on the metal surface and complies with the Langmuir adsorption isotherm. The potentiodynamic polarization analysis findings demonstrated that the extract of T. cordifolia mainly acted as a mixed inhibitor. The EIS study suggests that the T. cordifolia extract became effective by increasing the charge transfer resistance (Rct) by adsorbing on the steel surface. The FE-SEM study verified that T. cordifolia extract enhances the surface smoothness of the metal specimen. The adsorption mode of corrosion prevention is validated by the change in the chemical composition of the elemental surface examined by EDX studies. T. cordifolia extract mainly contains numerous aromatic phenolic compounds. FT-IR analysis confirmed the presence of several compounds with N and OH bonds in T. cordifolia extract. It has been established that T. cordifolia extract could be used for carbon steel in a marine environment.