Anti-corrosive properties of xanthone on mild steel corrosion in sulphuric acid: Experimental and theoretical investigations

I.B. Obot,N.O. Obi-Egbedi 한국물리학회 2011 Current Applied Physics Vol.11 No.3

The anti-corrosive effect of xanthone (XAN) on the corrosion of mild steel in 0.5 M H_2SO_4 has been studied by gravimetric and UV―visible spectrophotometric methods at 303―333 K. Results obtained revealed that XAN performed excellently as a corrosion inhibitor for mild steel in sulphuric acid solution. Inhibition efficiency increases with increase in concentration of XAN but decreases with rise in temperature which is suggestive of physical adsorption mechanism although chemisorption may also play a part. Dubinin―Radushkevich adsorption isotherm model was found to adequately describe the adsorption of XAN onto the mild steel surface. Kinetic parameters of activation and thermodynamic parameters using the statistical model were calculated and discussed. The corrosion process in 0.5 M H_2SO_4 in the absence and presence of XAN follows first-order kinetics. The UV―visible absorption spectra of the solution containing the inhibitor after the immersion of mild steel specimen indicate the formation of a XAN―Fe complex. Quantum chemical calculations have been performed using DFT and several quantum chemical indices were calculated and correlated with the inhibitive effect.

Enhanced corrosion inhibition effect of tannic acid in the presence of gallic acid at mild steel/HCl acid solution interface

I.B. Obot,A. Madhankumar 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.25 No.-

The corrosion inhibition behaviour of tannic acid (TA), gallic acid (GA) and their blends on mild steel in 1 M HCl solution was studied via electrochemical methods, namely, polarization (Tafel plots) and electrochemical impedance spectroscopy (EIS). The surface morphology of mild steel in 1 M HCl, TA alone, and in combination with GA was elucidated using scanning electron microscopy (SEM). The results show that TA can protect mild steel from acid corrosion better than GA. However, inhibition effect of TA can be enhanced by its combination with GA. The adsorption behaviour of TA against steel corrosion obeyed Langmuir adsorption isotherm. Furthermore, polarization results suggest that TA and GA blends behaves as mixed-type inhibitor of predominant anodic effect. EIS results reveal that the charge transfer resistance value of the steel inhibited by TA in combination with GA is significantly higher than that of steel inhibited by TA alone. The SEM images confirmed the enhanced film formation on the steel surface in the presence of TA and GA blended in the ratio 9:1 when compared with TA alone. Quantum chemical calculations have been used to provide insights into the mechanism of interaction of TA and GA on mild steel.

Theoretical prediction and electrochemical evaluation of vinylimidazole and allylimidazole as corrosion inhibitors for mild steel in 1M HCl

I.B. Obot,S.A. Umoren,Z.M. Gasem,Rami Suleiman,Bassam El Ali 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1

Corrosion inhibition potentials of two imidazole derivatives namely, vinylimidazole (VI) andallylimidazole (AI) for carbon steel in 1M HCl at 25 C were predicted theoretically using quantumchemical calculations and molecular dynamics (MD) simulations. DFT calculations indicated that VI ismore reactive towards steel surface than AI. Equilibruim adsorption behaviour of VI and AI molecules onFe2O3 (010) surface was investigated using molecular dynamics (MD) simulations. The equilibriumadsorption energy followed the order: VI > AI. Theoretical conclusions were subsequently validatedexperimentally using potentiodynamic polarization, linear polarization resistance, electrochemicalimpedance spectroscopy, and surface analytical techniques (SEM and AFM).

Inhibition of mild steel corrosion in acidic medium using coconut coir dust extracted from water and methanol as solvents

S.A. Umoren,I.B. Obot,AU Israel,P.O. Asuquo,M.M. Solomon,UM Eduok,A.P. Udoh 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.5

Corrosion inhibition of mild steel in H2SO4 by water and methanol extracts of coconut coir dust was studied using chemical and electrochemical techniques. It was found that the extracts inhibited the acid induced corrosion of mild steel. The inhibition efficiency increased with increase in extracts concentration but decreased with increase in temperature. Methanol extract was found to be a better inhibitor. The adsorption of the extracts’ components onto the mild steel surface follow Temkin and Freundlich adsorption isotherms for methanol and water extracts respectively. Polarization studies show that the extracts act as mixed typed inhibitor but under cathodic control.

Promising bio-composites of polypyrrole and chitosan: Surface protective and in vitro biocompatibility performance on 316L SS implants

Kumar, A.M.,Suresh, B.,Das, S.,Obot, I.B.,Adesina, A.Y.,Ramakrishna, S. Applied Science Publishers 2017 Carbohydrate Polymers Vol.173 No.-

Advanced biomedical materials can potentially be developed from combinations of natural biodegradable polymers and synthetic polymers. We synthesized bioactive composites based on polypyrrole/chitosan through in-situ electrochemical polymerization in oxalic acid medium. Surface characterization results revealed the influence of chitosan inclusion on polypyrrole (PPy) surface morphology. Contact angle results confirmed the enhancement in surface hydrophilicity due to the addition of chitosan into the PPy matrix. Electrochemical corrosion studies revealed that the composite coatings showed enhanced protective performance compared to pure PPy. Further, we investigated the effect of the composite coatings on the growth of MG-63 human osteoblast cells to assess their biocompatibility. Monte Carlo simulations were engaged to assess the interactions between the metal surface and composite coatings. The composite containing equal parts PPy and chitosan was found to be biocompatible; together with the corrosion protection results, the findings indicated that this bioactive coating material has potential for use in 316L SS implants.

Pyrimidine derivatives as novel acidizing corrosion inhibitors for N80 steel useful for petroleum industry: A combined experimental and theoretical approach

Jiyaul Haque,K.R. Ansari,Vandana Srivastava,M.A. Quraishi,I.B. Obot 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.49 No.-

The corrosion inhibition performance of two pyrimidine derivatives namely 5-styryl-2,7-dithioxo-2,3,5,6,7,8-hexahydropyrimido[4,5-d] pyrimidin-4(1H) one (PP-1) and 5-(2-hydroxyphenyl)-2,7-dithioxo-2,3,5,6,7,8-hexahydropyrimido[4,5-d]-pyrimidin-4(1H) one (PP-2) on N80 steel corrosion in15% HCl has been studied using gravimetric method, electrochemical impedance spectroscopy (EIS),potentiodynamic polarization, atomic force microscopy (AFM), scanning electron microscopy (SEM), DFT,molecular electrostatic potential and Monte Carlo simulation. The corrosion inhibition efficiencies atoptimum concentration (250 mg/L) are 89.1% (PP-1) and 73.1% (PP-2) respectively at 308 K. The corrosioninhibition efficiency increases with increase in concentration and decreases with temperature. PPsobeyed Langmuir adsorption isotherm. AFM and SEM analyses supported formation of protectivefilm onN80 steel in presence of inhibitors. DFT and Monte Carlo simulation calculations supported experimentalresults.

Pyranpyrazole derivatives as novel corrosion inhibitors for mild steel useful for industrial pickling process: Experimental and Quantum Chemical study

Parul Dohare,K.R. Ansari,M.A. Quraishi,I.B. Obot 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.52 No.-

In the present work three new corrosion inhibitors namely ethyl 6-amino-3-methyl-4-(p-tolyl)-2,4-dihydropyrano[2,3,C]pyrazole-5-carboxylate (EPP-1), ethyl 6-amino-3-methyl-4(phenyl)-2,4-dihydro-pyrano[2,3,C]pyrazole-5-carboxylate (EPP-2), ethyl 6-amino-3-methyl-4-(3-nitrophenyl)-2,4-dihydro-pyrano[2,3,C]pyrazole-5-carboxylate (EPP-3) were prepared, characterized and their corrosion inhibitionproperties on mild steel were investigated using gravimetric, potentiodynamic polarization andelectrochemical impedance spectroscopy (EIS). The surface morphology of the mild steel was examinedusing scanning electron microscopy (SEM) and atomic force microscopy (AFM). EPP-1 exhibited highestefficiency of 98.8% at 100 mg/L. AFM and SEM studies confirmed the formation of adsorbedfilm on themetal surface. The inhibitors followed the Langmuir adsorption isotherm. Density functional theory(DFT) was used to understand donor–acceptor relationship between inhibitors and metal. Theorientation and binding energy of inhibitor molecules were investigated using molecular dynamicsimulation (MD). A good relationship was obtained between theoretical and experimental results.