Corrosion inhibitors are chemical substances that, added at low concentration to a corrosive medium, slow the anodic or the cathodic reaction at a metal surface and lower the corrosion rate. Most organic inhibitors act by adsorption: heteroatoms, aromatic rings and alkyl chains anchor the molecule on the metal and the resulting film blocks the active sites, and both the thickness and the chemical state of that film can be followed by surface analytical methods [1]. Adsorption is commonly described by Langmuir-type isotherms, so the efficiency depends on the concentration, the temperature and the electrode potential rather than on the inhibitor alone [2]. Oxidising inorganic anions passivate the surface instead, and because several classical inhibitors are toxic, plant extracts, amino acids and ionic liquids have been examined as substitutes [3]. Reported efficiencies in acidic media often fall between 70 and 95 percent [4]. The measured efficiency also varies with the electrochemical method, the exposure time and the surface preparation, so values obtained under different protocols are not directly comparable, and the long-term stability of the adsorbed film remains an open question [5].
- corrosion inhibition
- adsorption
- carbon steel
- green inhibitor
- corrosion rate
- electrochemical impedance
References
- Wang, L.; Wang, H.; Seyeux, A.; Zanna, S.; Pailleret, A.; Nesic, S.; Marcus, P.; Adsorption mechanism of quaternary ammonium corrosion inhibitor on carbon steel surface using ToF-SIMS and XPS. Corrosion Science 2023, 213, 110952, 10.1016/j.corsci.2022.110952.
- Ai, J.; Guo, X.; Chen, Z.; The adsorption behavior and corrosion inhibition mechanism of anionic inhibitor on galvanic electrode in 1% NaCl solution. Applied Surface Science 2006, 253, 683-688, 10.1016/j.apsusc.2005.12.153.
- Zunita, M.; Rahmi, V.A.; Advancement of Plant Extract/Ionic Liquid-Based Green Corrosion Inhibitor. Chemistry Africa 2024, 7, 505-538, 10.1007/s42250-023-00782-5.
- Ji, G.; Anjum, S.; Sundaram, S.; Prakash, R.; Musa paradisica peel extract as green corrosion inhibitor for mild steel in HCl solution. Corrosion Science 2015, 90, 107-117, 10.1016/j.corsci.2014.10.002.
- Wang, F.; Zhang, Z.; Wu, S.; Jiang, J.; Chu, H.; Effect of Inhibitor on Adsorption Behavior and Mechanism of Micro-Zone Corrosion on Carbon Steel. Materials 2019, 12, 1901, 10.3390/ma12121901.