Anti-Corrosive Properties of Salvadora oleoides and Pennisetum typhoideum Extracts Against Mild Steel in Acidic Environment

Abstract

Corrosion causes the collapse of metallic structures such as bridges, buildings, and overpasses, as well as explosions in chemical industries. For the development of green corrosion inhibitors with using plants parts extract (leaf, root and stem) of Salvadora oleoidesandPennisetum typhoideumplants represent a significant advancement in sustainable materials science and environmental protection.The effectiveness of corrosion inhibition was investigated using potentiodynamic polarisation, thermometric approaches as well as surface analysis by SEM photograph. The low entropy and negative enthalpy values of the system, which show less randomness and more adsorption of the plant elements, clearly show that the corrosion process is exothermic.The values of free energy (?Gads) of adsorption for all the systems studied lie between -14.21561and -36.94375kJ mol?1 signifying spontaneous adsorption of the additives on the metal surface primarily due to physisorption.The SEM images of steel after immersion in 0.1 N HCl for 24 hours with 500 ppm concentration of plants parts extracts. The SEM images of untreated metal surface indicate the smooth metal surface, whereas SEM images of without inhibitor in acid solution exhibited manifest immense roughness with pits and cracks in structure which indicate that steel surface has been adversely affected. Finally conclude that, the present investigation has been effectively shown that plant extract is a corrosion inhibitor for steel in the presence of hydrochloric acid.

Introduction

Corrosion, as defined by IUPAC, is an irreversible, environment-dependent process in which materials—especially metals—deteriorate due to reactions such as oxidation. Moisture and oxygen are essential for corrosion to occur. Globally, corrosion causes massive economic losses equal to about 5% of the world GDP, and in India alone it costs nearly ?2 lakh crore annually. It also leads to structural failures and industrial accidents.

To address these issues in an eco-friendly way, green corrosion inhibitors, especially plant-based extracts, are gaining importance. These natural inhibitors are safer, more sustainable, and chemically diverse, offering effective protection by adsorbing onto metal surfaces and reducing corrosion.

This research studies the corrosion inhibition effectiveness of Salvadora oleoides and Pennisetum typhoideum plant extracts (leaf, root, stem) on steel in 0.1 N HCl. The extracts were prepared using ethanol, purified, and used in various concentrations (50–500 ppm). Corrosion inhibition was evaluated using:

• Potentiodynamic polarization

• Thermometric analysis

• Surface analysis via SEM

Key Findings

• Thermodynamic values showed negative Gibbs free energy (ΔGads), meaning adsorption of inhibitors on steel is spontaneous and mainly due to physisorption, with slight chemisorption.

• Positive enthalpy (ΔH) and low entropy (ΔS) values suggest an exothermic adsorption process with decreasing randomness.

• Higher inhibitor concentration improved corrosion resistance.

• Potentiodynamic tests revealed reductions in corrosion current density (icorr) and shifts in corrosion potential (Ecorr), confirming inhibition action. Most extract samples acted as mixed-type inhibitors, affecting both anodic and cathodic reactions.

• Stem extracts of both plants showed the highest inhibition efficiency.

• SEM images showed severe surface damage in uninhibited steel, whereas inhibited samples exhibited much smoother surfaces, confirming protective film formation.

Conclusion

Plant extracts from Salvadora oleoides and Pennisetum typhoideum act as effective green corrosion inhibitors for steel in acidic media. Their efficiency increases with concentration and immersion time, making them promising sustainable alternatives to conventional inhibitors.

References

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Copyright

Copyright © 2025 Kumawat Y, Mathur P , Sharma A . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.