Study on methylene dichloride and butanolic extracts of Reutera lutea (Desf.) Maire (Apiaceae) as effective corrosion inhibitions for carbon steel in HCl solution

Methylene dichloride extract (MDE) and n-butanolic extract (BE) of Reutera lutea (Desf.) Maire were investigated as corrosion inhibitors for carbon steel (CS) in 1.0 M HCl using weight loss and potentiodynamic polarization measurements, electrochemical impedance spectroscopy, and scanning electron microscopy techniques. The effect of temperature on the corrosion behavior of CS was studied in the range of 293–323 K. The experimental results show that MDE and BE are good corrosion inhibitors and the protection efficiency increased with increasing concentration of the extracts, but decreased with rise in temperature. The extracts behaved as mixed-type corrosion inhibitors with highest inhibition at 700 and 800 mg L−1 for MDE and BE, respectively. The adsorption of extracts on the CS surface was found to follow the Freundlich isotherm, and the adsorption mode was found to be physisorption. The free energies, enthalpies, and entropies for the adsorption process and the apparent energies, enthalpies, and entropies of the dissolution process are explained in detail.