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The efficacy of Rumex Nervosus Vahl Leaves Ethanolic extract (RNVLE) to inhibit C38 steel corrosion in one molar hydrochloric acid medium was examined using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. Polarization measurements revealed mixed-type inhibitor behavior. The inhibitory efficacy assessed by both polarization and (EIS) techniques was consistent, with an IE value of (96.0 %) and (95.5 %) at 2g/L of RNVLE, respectively. The RNVLE adsorption on the C38 metal surfaces in 1M HCl follows the Langmuir adsorption isotherm. The calculated free energy (G°ads equal to -16.1 KJ mol-1) explained that RNVLE controls the corrosion process by physisorption. The effect of immersion time was also investigated. This study demonstrated that RNVLE can be considered an excellent inhibitor up to 6 hours and after this time; it is considered a lower quality inhibitor although it still has sufficient inhibitory ability. SEM-EDX (Scanning Electron Microscopy and X-ray Energy Dispersive Spectroscopy) analysis revealed that the extract molecules adsorb on the metal's surface. These findings indicate that RNVLE can be used as an effective corrosion inhibitor for C38 steel in 1M HCl solution.

This work investigated the effect of temperature on corrosion of C38 steel in a hydrochloric medium (1M) in the absence and presence of the ethanolic extract from Eriobotrya Japonica (ERJ) seeds treated by maceration. For a better understanding of the corrosion process, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques had applied by increasing the temperature from 303.15 K to 333.15 K. Moreover, studying adsorption isotherms and determining thermodynamic parameters to understand the mechanism adopted in the adsorption of ERJ molecules on the metal surface. The results reveal that the inhibition efficiency increases with higher inhibitor concentration and decreases slightly with increasing temperature. Thus, the Langmuir model is the best model to fit the data obtained, and the adsorption follows a spontaneous physisorption process. According to the evolution of enthalpy, entropy, and activation energy, the inhibition capacity decreases is associated with a slow endothermic dissolution due to forming an active complex on the surface of C38.