Document Type : Original Article
Department of Humanities and Sciences, Gokaraju Rangaraju Institute of Engineering and Technology, Hyderabad, Telangana, India
Department of Chemistry, PSGR Krishnammal College for Women, Coimbatore, TamilNadu, India
Laboratory of Materials, Nanotechnology, and Environment, Faculty of Sciences, Mohammed V University in Rabat, Av. Ibn Battouta, P.O. Box. 1014 Agdal-Rabat, Morocco
Laboratory of Advanced Materials and Process Engineering, Faculty of Sciences, Ibn Tofail University, P.O. Box. 133, 14000, Kenitra, Morocco
Department of Chemistry, AN-Najah National University, P.O. Box 7, Nablus, Palestine
The present work deals with the corrosion inhibition mechanism of mild steel in 1 M H2SO4 employing the new carbonitrile derivative viz. 2-amino-4-(4-hydroxyphenyl)-6-(p-tolyl)-4H-pyran-3-carbonitrile (HCN). A such mechanism was elicited by means of the potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques and weight loss (WL). The experimental results revealed maximal inhibition efficiency (IE) rates up to 92.4% in weight loss. WL measurement revealed a decrease in corrosion rate with increasing concentration of corrosion inhibitor and decreasing with increasing temperature up to 333 K. The Nyquist curves indicated that the corrosion inhibition was controlled by a charge transfer process whereas the PDP curves showed that the HCN behaved as a mixed-type corrosion inhibitor. The Langmuir isotherm was used to determine the adsorption thermodynamic parameters. Thermodynamic characteristics for activation and adsorption were determined and discussed. Adsorption free energy at 303 K ( = -22.26 kJ mol-1 for HCN) indicated a combination of chemisorption and physisorption. The inhibitor (HCN) formed a protective layer that acted as a barrier between the surface of the metal and the acid medium which was investigated through surface studies like Scanning Electron Microscopy (SEM) coupled with Energy dispersive X-ray analysis (EDS). The surface studies were in coincidence with weight loss and electrochemical studies. Density functional theory (DFT) was performed to support the experimental data in an aqueous medium using the basis set 6-311G(d,p). From the Mulliken population analysis, the adsorption sites have been studied and the results of DFT were steady with the experimental studies.