Adsorption of eco-friendly carthamus tinctorius on steel surface in saline solution: A combination of electrochemical and theoretical studies

Abstract

In this study, the different parts of carthamus tinctorius plant, including petal (SPE), leaf (SLE), and shoot (SSE), have been extracted. Adsorption of the extracts on mild steel in 3.5 wt. % NaCl solution was evaluated employing electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and electrochemical noise measurements (EN). The field-emission scanning electron microscopy (FE-SEM) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) were employed to appraise the morphology of the samples surface subjected to the test solutions. According to the EIS results, the maximum adsorption efficiency belonged to the solution containing 1 g L−1 of petal extract. Polarization test results demonstrated a mixed-type inhibition with dominant anodic inhibition. The maximum inhibition efficiency resulted from SPE (84 %(while for the SLE and SSE it was around 60 % and 44 %, respectively. Moreover, the results obtained from FE-SEM showed that the organic compounds could effectively be adsorbed on the anodic sites and establish inhibitive film over the steel surface. Furthermore, molecular dynamics (MD) and Monte Carlo (MC) simulation methods applied on different components of the SPE revealed their adsorption onto steel substrates via donor-acceptor adhesion mechanism.