Emeka E. Oguzie

Gum arabic as a potential corrosion inhibitor for aluminium in alkaline medium and its adsorption characteristics

Purpose – To investigate the inhibitive effect of gum arabic (GA) for the corrosion of aluminium in alkaline (NaOH) medium and determine its adsorption characteristics. The present work is another trial to find a cheap and environmentally safe inhibitor for aluminium corrosion.Design/methodology/approach – The inhibition efficiency (%I) has been evaluated using the hydrogen evolution (via the gasometric assembly) and the thermometric methods at 30 and 40°C. The concentrations of GA (inhibitor) used were 0.1‐0.5 g/l and the concentrations of NaOH (the corrodent) were 0.1‐2.5 M. The mechanism of adsorption inhibition and type of adsorption isotherms were proposed from the trend of inhibition efficiency with temperature, Ea, ΔGads and Qads values.Findings – GA inhibited the corrosion of aluminium in NaOH solutions. The inhibition efficiency increased with increase in GA concentration and with increase in temperature. Phenomenon of chemical adsorption is proposed for the inhibition and the process followed th...

Adsorption and corrosion-inhibiting effect of Dacryodis edulis extract on low-carbon-steel corrosion in acidic media

The inhibition of low-carbon-steel corrosion in 1M HCl and 0.5M H(2)SO(4) by extracts of Dacryodis edulis (DE) was investigated using gravimetric and electrochemical techniques. DE extract was found to inhibit the uniform and localized corrosion of carbon steel in the acidic media, affecting both the cathodic and anodic partial reactions. The corrosion process was inhibited by adsorption of the extracted organic matter onto the steel surface in a concentration-dependent manner and involved both protonated and molecular species. Molecular dynamics simulations were performed to illustrate the process of adsorption of some specific components of the extract.

Inhibition of acid corrosion of mild steel by Telfaria occidentalis extract

Purpose – To investigate the efficacy of Telfaria occidentalis extract as a corrosion inhibitor for mild steel in 2 M HCl and 1 M H2SO4 solutions, respectively, and to assess the effect of temperature and halide additives on the inhibition efficiency.Design/methodology/approach – Corrosion rate was monitored by careful volumetric measurement of the evolved hydrogen gas at fixed time intervals. Inhibition efficiency was determined by comparing the corrosion rates in the absence and presence of additive. Attempts were made to elucidate the inhibition mechanism from the trend of inhibition efficiency with temperature. The adsorption mode of inhibiting species in the extract was assessed by considering the influence of both acid and halide ions on inhibition efficiency.Findings – Telfaria occidentalis extract inhibited mild steel corrosion in 2 M HCl and 1 M H2SO4 solutions. Inhibition efficiency increased with extract concentration but decreased with rise in temperature. Synergistic effects increased the eff...

Corrosion inhibition and adsorption behaviour of Ocimum basilicum extract on aluminium

Purpose – To appraise the inhibiting effect of Ocimum basilicum extract on aluminium corrosion in 2 M HCl and 2 M KOH solutions, respectively, at 30 and 60°C.Design/methodology/approach – Corrosion rates were determined using the gas‐volumetric technique and the values obtained in absence and presence of extract was used in calculation of the inhibition efficiency. The mechanism of inhibition was estimated from the trend of inhibition efficiency with temperature.Findings – Ocimum basilicum extract was found to inhibit aluminium corrosion in the acidic and alkaline environments. Inhibition efficiency increased with extract concentration but decreased with rise in temperature, suggesting physical adsorption of the organic matter on the metal surface. These results were corroborated by kinetic and activation parameters for corrosion and adsorption processes evaluated from the experimental data at the temperatures studied. Halide additives synergistically improved the inhibition efficiency of the extract.Orig...

Adsorption and corrosion inhibitive properties of Azadirachta indica in acid solutions

Purpose – To assess the protective effect and adsorption behaviour of Azadirachta indica extract in controlling mild steel corrosion in 1 M H2SO4 and 2 M HCl.Design/methodology/approach – The inhibitive effect of the plant extract was monitored using the gas‐volumetric technique. The inhibition mechanism was inferred by curve fitting of the experimental data to known adsorption isotherms and the trend of inhibition efficiency with temperature.Findings – Azadirachta indica extract effectively inhibited steel corrosion in the acid media studied by virtue of adsorption. The inhibitor adsorption characteristics were approximated by Langmuir isotherm. The extract functioned as a mixed inhibitor, depending on its concentration. The prime effect at lower concentration was mitigation of the cathodic reaction by physical adsorption of protonated species in the extract and at higher concentration the anodic reaction was inhibited by chemisorption of molecular species.Originality/value – This paper provides novel in...

Effect of Gongronema latifolium extract on aluminium corrosion in acidic and alkaline media

Purpose – This paper aims to appraise the effectiveness of Gongronema latifolium extract as an environmentally friendly corrosion inhibitor for aluminium in strong acid (2 M HCl) and alkaline (2 M KOH) environments.Design/methodology/approach – Corrosion rates were determined using the gas‐volumetric technique. The efficiency of inhibition was estimated by comparing corrosion rates in absence and presence of the additive, while the mechanism of inhibition was assessed by considering temperature effects on corrosion and inhibition processes.Findings – The results show that the extract was well adsorbed on the metal surface and significantly repressed aluminium corrosion in both environments. Inhibition efficiency generally increased with concentration up to maximum values of 97.54 and 90.82 per cent in 2 M HCl and 2 M KOH, respectively. Temperature dependence studies revealed that the extract was chemically adsorbed on the aluminium surface at all concentrations in 2 M HCl and physically adsorbed in 2 M KO...

Theoretical and experimental studies on the corrosion inhibition potentials of some purines for aluminum in 0.1 M HCl.

Experimental aspect of the corrosion inhibition potential of adenine (AD), guanine (GU) and, hypoxanthine (HYP) was carried out using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods while the theoretical aspect of the work was carried out by calculations of semi-empirical parameters (for AM1, MNDO, CNDO, PM3 and RM1 Hamiltonians), Fukui functions and inhibitor–metal interaction energies. Results obtained from the experimental studies were in good agreement and indicated that adenine (AD), guanine (GU) and hypoxanthine (HYP) are good adsorption inhibitors for the corrosion of aluminum in solutions of HCl. Data obtained from electrochemical experiment revealed that the studied purines functioned by adsorption on the aluminum/HCl interface and inhibited the cathodic half reaction to a greater extent and anodic half reaction to a lesser extent. The adsorption of the purines on the metal surface was found to be exothermic and spontaneous. Deviation of the adsorption characteristics of the studied purines from the Langmuir adsorption model was compensated by the fitness of Flory Huggins and El Awardy et al. adsorption models. Quantum chemical studies revealed that the experimental inhibition efficiencies of the studied purines are functions of some quantum chemical parameters including total energy of the molecules (TE), energy gap (EL–H), electronic energy of the molecule (EE), dipole moment and core–core repulsion energy (CCR). Fukui functions analysis through DFT and MP2 theories indicated slight complications and unphysical results. However, results obtained from calculated Huckel charges, molecular orbital and interaction energies, the adsorption of the inhibitors proceeded through the imine nitrogen (N5) in GU, emanine nitrogen (N7) in AD and the pyridine nitrogen (N5) in HPY.

Pyrimidine-2-thione derivatives as corrosion inhibitors for mild steel in acidic environments

The inhibition of mild steel corrosion in 1.0 M sulphuric acid by pyrimidine-2-thione derivatives (4,6-diphenyl-3,4-dihydropyrimidine-2(1H)-thione (PTH); 4-(4-methylphenyl)-6-phenyl-3,4-dihydropyrimidine-2(1H)-thione (PTM) and 4-(4-methoxyphenyl)-6-phenyl-3,4-dihydropyrimidine-2(1H)-thione (PTMO)) has been investigated using weight loss and electrochemical techniques (potentiodynamic polarization and electrochemical impedance spectroscopy (EIS)). All the compounds effectively hindered the corrosion process by becoming adsorbed on the metal surface, following the Langmuir isotherm. Computational studies were undertaken to provide mechanistic insight into the roles of the different substituents on the corrosion inhibition and adsorption behavior of the studied compounds.

Experimental and theoretical assessment of the inhibiting action of Aspilia africana extract on corrosion aluminium alloy AA3003 in hydrochloric acid

The adsorption of Aspilia africana extract and subsequent corrosion inhibition of aluminium alloy AA3003 in hydrochloric acid solutions have been investigated using gravimetric and electrochemical techniques. Inhibition efficiency increased with extract concentration and temperature rise. Polarization studies revealed that the extract essentially inhibited the cathodic reaction. An adsorption mechanism involving physisorption and chemisorption of extract constituents at low and high temperatures, respectively, has been proposed from the trend of adsorption-free energies. Quantum chemical computations and molecular dynamics simulations described the individual contributions of some extract constituents to the observed inhibiting effect.

Broad spectrum corrosion inhibition: corrosion and microbial (SRB) growth inhibiting effects of Piper guineense extract

To assess the prospect of exploiting biomass extracts for the simultaneous control of chemical- and microbial-influenced corrosion, we herein describe experimental and computational studies to probe the corrosion inhibition and biocidal efficacy of aqueous extracts of Piper guineense (PG). Proximate phytochemical analysis of PG revealed the presence of alkaloids (3.1%), tannins (0.9%) and saponins (11.0%). The corrosion-inhibiting effect of the extract was appraised on low-carbon steel corrosion in 1-M HCl and 0.5-M H2SO4 using gravimetric and electrochemical techniques, whereas the agar disc diffusion method was employed to determine the biocidal effect of the extract on the corrosion-associated sulfate-reducing bacteria (SRB), Desulfotomaculum species. PG was found to be an excellent inhibitor for both corrosion and SRB growth. Both effects are attributed to the phytochemical constituents present in the extract. The corrosion process was inhibited by adsorption of the extract organic matter on the steel surface, whereas the antimicrobial effect results from disruption of the growth and essential metabolic functions of the SRB. We have relied on quantum chemical computations and molecular dynamics simulations to highlight the individual contributions of some extract constituents to the observed corrosion-inhibiting effect.