Evaluation of Thymus vulgaris plant extract as an eco-friendly corrosion inhibitor for stainless steel 304 in acidic solution by means of electrochemical impedance spectroscopy, electrochemical noise analysis and density functional theory.

Inhibition performance of Thymus vulgaris plant leaves extract (thyme) as environmentally friendly (green) inhibitor for the corrosion protection of stainless steel (SS) type 304 in 1.0molL-1 HCl solution was studied by potentiodynamic polarization, electrochemical impedance (EIS) and electrochemical noise measurements (EN) techniques. The EN data were analyzed with FFT technique to make the spectral power density plots. The calculations were performed by MATLAB 2014a software. Geometry optimization and calculation of the structural and electronic properties of the molecular system of inhibitor have been carried out using UB3LYP/6-311++G∗∗ level. Moreover, the results obtained from electrochemical noise analysis were compared with potentiodynamic polarization and electrochemical impedance spectroscopy. All of the used techniques showed positive effect of green inhibitor with increasing inhibitor concentration.