Rajesh Ranjan Sinha

Corrosion inhibition effect of spiropyrimidinethiones on mild steel in 15% HCl solution: insight from electrochemical and quantum studies

The effect of synthesized spiropyrimidinethiones, namely, 6′-(4-methoxyphenyl)-1′-phenyl-2′-thioxo-2′,3′-dihydro-1′H-spiro[indoline-3,4′-pyrimidine]-2-one (MPTS) and 6′-(4-methoxyphenyl)-1′-phenyl-2′-thioxo-2′,3′-dihydro-1′H-spiro[indoline-3,4′-pyrimidine]-2-one (CPTS) on the corrosion of mild steel in 15% HCl solution was investigated by using weight loss and electrochemical methods. Both inhibitors act as mixed inhibitors and their adsorption on mild steel obeyed Langmuirs adsorption isotherm. The potential of zero charge (EPZC) for the mild steel was determined by electrochemical impedance spectroscopy methods. Scanning electron microscopy, energy dispersion X-ray spectroscopy, FTIR, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy were used to characterize the surface morphology of the uninhibited and inhibited mild steel specimens. Density Functional Theory (DFT) was employed for theoretical calculations.

Corrosion inhibition effect of pyrazole derivatives on mild steel in hydrochloric acid solution

Synthesized compounds, namely methyl 5-(4-Chlorobenzoyloxy)-1-phenyl-1H-pyrazole-3-carboxylate (MCPPC) and 5-(4-methoxyphenyl)-3-(4-methylphenyl)4,5-dihydro-1H-pyrazol-1-yl-(pyridin-4-yl)methanone (MMDPPM) were investigated as corrosion inhibitor for mild steel (MS) in 15% HCl solution using weight loss measurement, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) methods. Inhibition efficiency was found concentration-dependent and increased by increasing the concentration of MCPPC and MMDPPM. Both of inhibitors were efficient even at a very low concentration of 25 ppm. The inhibitors MCPPC and MMDPPM showed inhibition efficiency of 67.1 and 76.8%, respectively, at 25 ppm, whereas it was 92.0 and 95.9%, respectively, at 250 ppm concentration at 303 K. The potentiodynamic polarization curves showed that MCPPC and MMDPPM act as mixed-type inhibitor in 15% HCl solution. The Nyquist plots showed that charge transfer resistance increased and double-layer capacitance decreased on increasing the concentration of studied inhibitors due to adsorption of inhibitor molecules on MS surface. The adsorption of each inhibitor on MS surface obeys Langmuir adsorption isotherm. On the basis of thermodynamic adsorption parameters, mixed-type adsorption (physisorption and chemisorption) for the studied inhibitors on MS surface was suggested. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and atomic force microscopy (AFM) analyses confirmed the existence of a protective film of the inhibitor on MS surface. The density functional theory was employed for theoretical calculations, and the obtained results were found to be consistent with the experimental findings.

Experimental and Theoretical Studies on Synthesized Compounds as Corrosion Inhibitor for Mild Steel in Hydrochloric Acid Solution

Imidazole derivatives, namely, 1-((1-(piperazinomethyl)-1H-benzoimidazol-2-yl)methyl)-2-phenylhydrazine (PBIP), and 1-((1-(morpholinomethyl)-1H-benzoimidazol-2-yl)methyl)-2-phenylhydrazine (MBIP) were synthesized and investigated as inhibitors for mild steel corrosion in 15% HCl solution using weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. It was found that the inhibition efficiency of both the inhibitors increases with increase in concentration of inhibitors and decreases with increase in temperature. The inhibitors, PBIP and MBIP, show corrosion inhibition efficiency of 92.6% and 91.4% at 300 ppm concentration, respectively, at 303 K. Polarization studies showed that both the studied inhibitors were of mixed type in nature. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were performed for surface study of uninhibited and inhibited mild steel samples. The semi-empirical AM1 method was employed for theoretical calculations.

Adsorption properties and inhibition of mild steel corrosion in 15% HCl by 3-((1H-indol-3-yl)(4-methoxyphenyl)methyl)-1H-indole:electrochemical study

The inhibiting effect of 3-((1H-indol-3-yl)(4-methoxyphenyl)methyl)-1H-indole (IMMI) on the corrosion of mild steel (MS) in 15% HCl solution has been studied by using potentiodynamic polarization technique. The polarization data revealed that IMMI acts as a mixed type inhibitor for mild steel in acid solution.. The adsorption of the inhibitors on the mild steel surface was found to obey Langmuirs adsorption isotherm. Inhibition efficiency was found to be greater than 95% and inhibition is governed by both physical adsorption and chemisorption mechanism.