Coconut dust extract as a pitting corrosion inhibitor for reinforcing steel in concrete in the presence of chlorides

• C.N. Linh¹, D.S. Shevtsov², I.D. Zartsyn², N.V. Chi¹, N.D. Anh¹, N.V. Hoa³, N.N. Hung¹ and O.A. Kozaderov²

¹ Coastal Branch, the Joint Vietnam-Russia Tropical Science and Technology Research Center, 30 Nguyen Thien Thuat, Nha Trang, Vietnam
² Faculty of Chemistry, Voronezh State University, Universitetskaya pl. 1, 394018 Voronezh, Russian Federation
³ Nha Trang University, 02 Nguyen Dinh Chieu, Nha Trang, Vietnam

Abstract: This study aimed to evaluate the inhibitory effect of coconut dust extract on the pitting corrosion of reinforcing steel in concrete via potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and weight loss measurements. Different solvents (water, ethanol, methanol, and acetone) were used for the extraction of coconut dust, in which water indicated the most efficiency due to the highest content of flavonoids, tannins, polyphenols, saponins, phlobatannins, and anthraquinones. Then, the obtained coconut dust extract was tested in two cases: (i) mixing with a water extract obtained from concrete with the addition of 3% NaCl and (ii) adding to the mortar-making process before immersing it in a 3% NaCl solution. In the first case, the highest efficiency of ~95% (from PDP), ~99% (from EIS), and ~89% (from weight loss) were obtained using the inhibitor concentration of 1.5 g/L. In the second case, the efficiency was increased at inhibitor concentrations of ≥0.5 g/L. The highest efficiency is ~95% (from weight loss) and ~97% (from PDP) at a concentration of 2.0 g/L. The findings indicated the high potential of coconut dust extract as a green corrosion inhibitor for the corrosion of reinforcing steel in concrete in the presence of chlorides.

Keywords: coconut dust extract, green corrosion inhibitor, pitting corrosion, reinforcing steel, concrete

Int. J. Corros. Scale Inhib., 2024, 13, no. 3, 1571-1589
doi: 10.17675/2305-6894-2024-13-3-12

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