Inhibition of copper corrosion in sodium chloride solution by Padina pavonica (Linnaeus) Thivy algal extracts

• I. Drventić^1,2, A. Nagode³, I.G. Mekinić⁴ and I. Smoljko²

¹ Department of Analytical Chemistry, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia
² Department of Electrochemistry and Materials Protection, Faculty of Chemistry and Technology, University of Split, Ruđera Boškovića 35, 21000 Split, Croatia
³ Department of Materials and Metallurgy, Faculty of Natural Science and Engineering, University of Ljubljana, Aškerčeva cesta 12, 1000 Ljubljana, Slovenia
⁴ Department of Food Technology and Biotechnology, Faculty of Chemistry and Technology, University of Split, Ruđera Boškovića 35, 21000 Split, Croatia

Abstract: This study examined the inhibition efficiency of the phenolics from brown algae Padina pavonica (Linnaeus) Thivy ethanolic extract against the corrosion of copper in the 0.5 mol/l sodium chloride (NaCl) solution. The phenolics of P. pavonica were extracted by ultrasound-assisted extraction using different solvent systems (25, and 75% (v/v) of ethanol in water). The total phenolic content (TPC) of the extracts was determined spectrophotometrically. The 75% ethanolic extract exhibited the highest TPC and it was selected for studying its inhibition properties on copper corrosion in NaCl solution by electrochemical methods at various concentrations of the algal extract and temperatures. The results show that the algal extract performed very well as a mixed-type copper corrosion inhibitor in the test solution, with inhibition efficiency increasing with concentration and temperature. The maximum inhibition efficiency was 93.11% for an algal extract of 1.4% v/v at 303 K. The evaluation of the adsorption and activation parameters indicated a spontaneous mixed physical and chemical adsorption of this inhibitor on the copper surface which obeyed Langmuir adsorption isotherm. Furthermore, studies using a scanning electron microscope/energy-dispersive X-ray spectroscope (SEM/EDS) confirmed the calcification of P. pavonica. They showed that, under particular circumstances, a protective layer formed on the surface of the copper specimen. The findings advance the understanding of marine algae as a natural source of corrosion inhibitors and highlight the potential benefits of P. pavonica phenolics in preventing copper corrosion.

Keywords: brown algae, Padina pavonica, phenolics, corrosion inhibition, copper, electrochemical tests, adsorption mechanism

Int. J. Corros. Scale Inhib., 2024, 13, no. 2, 1208-1229
doi: 10.17675/2305-6894-2024-13-2-30

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