EXPERIMENTAL AND THEORETICAL INVESTIGATION OF VITEX DONIANA LEAVE EXTRACT AS CORROSION INHIBITOR FOR COPPER IN 3.5% NaCl SOLUTION

The inhibition effect of Vitex doniana (VD) leaves extract on the corrosion of copper in 3.5% NaCl solution has been investigated by weight loss, polarization technique and quantum chemical calculations. Results obtained reveal that the leaves extract gave good inhibition efficiency on copper corrosion. Weight loss results showed that the corrosion inhibition potentials of VD leaves extract decreased with increase in temperature but increased in inhibitor concentration. Tafel polarization studies have shown that VD leaves extract suppresses both the cathodic and anodic processes and thus it acts as mixed-type inhibitor without altering the corrosion mechanism of copper. The effect of temperature on the corrosion behaviour of copper in 3.5% NaCl in presence of different concentrations of the inhibitors was studied in the temperature range 30–60°C. The associated activation thermodynamic parameters have been determined. and values show that the adsorption process is spontaneous and involves electrostatic interactions between the inhibitor molecules and CU131729 surface via physical adsorption. The formation of film layer due to electrostatic interaction essentially blocks cathodic reactions and retards anodic dissolution of the metal. Molecular dynamics simulation was used to model the adsorption of a single inhibitor molecule on the copper surface from gas phase. The computational studies confirmed the corrosion inhibiting potential of VD leaves extract. The adsorption energies estimated via molecular dynamic stimulation suggests a spontaneous physical adsorption process. All theoretical calculations were carried out using Dmol3 basis set for all atoms.