Valeriana officinalis root extract as a green corrosion inhibitor for carbon steel in 1.0 M hydrochloric acid solution

In recent years, a large number of synthetic compounds have been reported as corrosioninhibitors. Although synthetic compounds exhibit good anti-corrosion properties, most of themare very toxic to the environment and human life. The toxic effects of synthetic compounds haveled to the replacement of natural products as anti-corrosion materials [1-3]. In this study, thecorrosion inhibition characteristics of Valeriana officinalis root extract (VFRE) wereinvestigated on carbon steel immersed in 1 M HCl media. The corrosion inhibition performanceof VFRE was evaluated by means of weight loss, potentiodynamic polarization andelectrochemical impedance spectroscopy (EIS) methods. Weight loss experiments were done as afunction of the VFRE concentration and immersion time in 1.0 M HCl solution. The highestinhibition efficiency of 94.7 % was obtained in the presence of 1.0 g L-1 VFRE after about 10hours of immersion time which shows that this extract is a fairly good inhibitor. Polarizationcurves indicated that VFRE is a mixed (cathodic/ anodic) type inhibitor. The effect oftemperature on the efficiency of VFRE was done by electrochemical polarization method in therange of 35-65°C. Adsorption of VFRE on the surface of carbon steel, in this range oftemperature, follows the Langmuir adsorption isotherm. It is guessed that the presence ofvalrenic acid, valerenol, and valernyl acetate containing extract decreases the corrosion rate ofcarbon steel in acidic solution. Therefore, theoretical methods such as quantum mechanics (QM)and molecular dynamics simulations (MDS) were used for suggest how the absorption of thesemolecules on the surface. MDS method evidenced that all major constituents exist in VFRE canbe adsorbed to steel surface and form a protective film on the surface of carbon steel.

Keywords:

Carbon steel , Hydrochloric Acid , Valeriana Officinalis Root Extract , Electrochemical Polarization Method , Electrochemical Impedance Spectroscopy , Molecular Dynamics