Inhibition effect of Cynara cardunculus leaf extract on corrosion of St37 steel immersed in seawater with and without bleach solution

Abstract

The inhibition performance of an aqueous extract of Cynara cardunculus leaves on the corrosion of St37 steel immersed in seawater and seawater with bleach was investigated using weight loss measurements, electrochemical methods, and surface characterization techniques. It was found that the extract components acted primarily as a mixed-type inhibitor, and inhibition efficiency increased with increasing inhibitor concentration. Electrochemical impedance spectroscopy (EIS) and dynamic electrochemical impedance spectroscopy (DEIS) confirmed the formation of a protective layer on the metallic surface in both solutions. The adsorption of inhibiting molecules conformed to the Langmuir isotherm model. The thermodynamic parameter values indicated that chemisorption constituted the major contribution to the adsorption process. This result was corroborated by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analyses. The significant inhibition effect can be related to the large amount of phenolic compounds in the CC aqueous extract as revealed by the Fourier-transform infrared (FTIR) spectrum.