Using natural plant extracts on metallic substances is the most frequently studied green corrosion inhibition approach in corrosion science. In this work, Coriaria nepalensis Stem Alkaloid (CNSA) has been successfully extracted and characterized by qualitative chemical (Mayer’s and Dragendroff’s) test and spectroscopic (UV and FTIR) measurement. CNSA has been employed as a green inhibitor for Mild Steel (MS) corrosion subjected to 1 M H2SO4 solution. The corrosion inhibition efficacy has been assessed by weight loss and polarization measurement methods. The effect of inhibitor concentration, immersion period, and temperature on the inhibition efficiency for the MS immersed in both acid and inhibitor solutions of different concentrations have been investigated. The maximum inhibition effect observed for CNSA is 96.4% for MS immersed in 1000 ppm inhibitor solution for 6 h at 18 °C by the weight loss measurement method. Similarly, the polarization measurement method observed a 97.03% inhibition efficiency for MS immersed for 3 h. The adsorption of inhibitor molecules on the MS surface aligns with the Langmuir model. The free energy of adsorption obtained is −28.75 kJ/mol indicating physical adsorption dominance over chemical adsorption. These findings suggested that CNSA has greater potential as an efficient green inhibitor.

Extract of Shorea robusta bark as a novel green inhibitor for mild steel (MS) corrosion has been investigated. Qualitative chemical tests, UV, and FTIR measurements were carried out to confirm phytochemicals in the extract. Gravimetric as well as electrochemical methods were employed to examine the inhibition efficiency of the extract. Effects of inhibitor concentration, immersion time as well as working temperature were investigated by weight loss measurement method. Weight loss measurement reveals the maximum inhibition efficiency of 1000 ppm inhibitor for half an hour immersion time. Also, 1000 ppm inhibitor can work up to a temperature of 55°C with 50% efficiency. Electrochemical measurements reflected the mixed type of inhibition behavior of the inhibitor. Polarization measurement results, the 93.73% and 75%, respectively for as-immersed and immersed samples in1000 ppm inhibitor concentration. Based on these findings, it is revealed that the Shorea robusta bark extract could be used as low temperature inhibitor.

Green corrosion inhibitors are of great interest due to their exciting and environmentally friendly behavior in mild steel corrosion control during and after the acid cleaning process. Herein, alkaloids were extracted from the stem of Ageratina adenophora and were ensured by qualitative chemical tests as well as spectroscopic test methods. The corrosion inhibition efficacy of the alkaloids against mild steel corrosion was evaluated by gravimetric, electrochemical and EIS measurement methods. In addition, the adsorption isotherm, free energy of adsorption and thermodynamic parameters of the process were evaluated. The investigations indicated the most promising inhibition efficacy of the alkaloids for mild steel corrosion. The adsorption isotherm study revealed that the adsorption of inhibitor molecules on the MS interface was manifested by dominant physisorption followed by chemisorption. Free energy and thermodynamic parameters are well suited to endothermic processes.

The residual ions of the acid cleaning processes induce the further corrosion of the metals, and this could be minimized using green inhibitors. Alkaloids extracted from plant parts could be cost effective and efficient inhibitors. In this work, alkaloids from Solanum xanthocarpum stem were successfully extracted, and they were characterized by qualitative chemical tests and spectroscopic measurements. As-extracted alkaloids were employed as green corrosion inhibitors for mild steel. The effectiveness of the inhibitor was determined by the weight loss and electrochemical measurement methods. From the weight loss measurement, the maximum inhibition efficiency of 93.14% was achieved. The temperature effect study revealed that the inhibitor can work up to a temperature of 58 °C. This could be one of the highest working temperatures among the reported green inhibitors. The electrochemical measurement reveals that the alkaloids could inhibit effectively up to 98.14% of the corrosion and serve as a mixed-type green inhibitor. A study on the kinetic parameters reflects that the inhibitor forms a potential barrier for the protection of a mild steel surface against corrosion. The values obtained from the thermodynamic parameters study reflect that the process is a spontaneous endothermic process. Based on the findings, it is revealed that the alkaloids extracted from S. xanthocarpum can serve as an excellent, eco-friendly and a promising green inhibitor against mild steel corrosion.