Abstract
In this work, Henna leaves extract (HLE) and its principal derivatives of Lawsone and Gallic acid are examined as green corrosion inhibitors. Our contribution is to quantify the effectiveness of HLE, Lawsone and Gallic acid on the corrosion inhibition of steel in simulated concrete pore solution (SCPS) containing 0.5 M NaCl, using electrochemical methods as open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy. In addition, environmental scanning electron microscopy, coupled to the energy dispersive X-ray microanalysis, was performed to investigate the morphology of the steel surface immersed in SCPS containing green inhibitors. Results highlight a synergistic effect with the formation of a protective layer on the steel surface by forming inhibitor-metal complexes. The HLE and Gallic acid act as anodic corrosion inhibitors and Lawsone behaves as a mixed type. These inhibitors are adsorbed on the steel surface by chemisorption according to the adsorption isotherm of Langmuir. The maximal inhibition efficiency is about 93% obtained at 0.2 g/L of HLE, which represents the higher effectiveness compared to Lawsone and Gallic acid.
Graphical Abstract
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Acknowledgments
The authors gratefully acknowledge the E.O.L.E laboratory, University of Tlemcen and the Directorate-General for Scientific Research and Technological Development (DG-RSDT-Algeria) for supporting this work. We also thank Dr. Egle Conforto from the LaSIE UMR CNRS 7356, La Rochelle University for performing the SEM images.
Disclosure statement
No potential conflict of interest was reported by the authors.