Optimal Inhibition Efficiency Research Articles

Evaluation of pawpaw leaves extract as anti-corrosion agent for aluminium in hydrochloric acid medium

Pawpaw leaves extract was examined as anti-corrosion agent for aluminium in hydrochloric acid medium. The extract and corrosion product were analyzed using Fourier transform infrared spectrophotometer (FTIR). Thermometric, gravimetric, potentiodynamic polarization and scanning electron microscopic methods were employed in the study. The inhibition efficiency was optimized using Response Surface Methodology (RSM) of Design Expert Software 9. Inhibitor concentration (0.2 g/l – 1.0 g/l), temperature (303 K – 333 K) and time (1hour - 5 hours) were the considered factors. It was revealed that stretched C-H and O-H functional groups were predominantly responsible for the corrosion inhibition process. The adsorption of the extract on the aluminium surface adhered to the mechanism of physical adsorption. A quadratic model adequately described the inhibition process. Optimum inhibition efficiency of 80.58% was obtained at inhibitor concentration of 0.961 g/l, temperature of 311.459 K and time of 3.932 hrs. The extract is a mixed-type inhibitor that can control both cathodic and anodic corrosion. http://dx.doi.org/10.4314/njt.v36i2.241

Carboxymethyl Cellulose/Silver Nanoparticles Composite: Synthesis, Characterization and Application as a Benign Corrosion Inhibitor for St37 Steel in 15% H2SO4Medium

This study has been designed to boost the inhibition efficiency and stability of carboxymethyl cellulose (CMC) and this objective has been achieved by incorporating silver nanoparticles (AgNPs) generated in situ by reduction of AgNO3 using natural honey into CMC matrix. Characterization of CMC/AgNPs composite was done using transmission electron microscope (TEM), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible spectroscopy (UV-vis), scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDS). Weight loss, electrochemical (dynamic electrochemical impedance spectroscopy, electrochemical impedance spectroscopy, and potentiodynamic polarization) supported by surface assessment (SEM, atomic force microscope, and FTIR) techniques are deployed for the anticorrosion studies of CMC/AgNPs on St37 specimen in 15% H2SO4 medium. CMC/AgNPs performs better than CMC. At 25 °C, optimum inhibition efficiency of 93.94% is afforded by 1000 ppm of CMC/AgNPs from DEIS method. Inhibition efficiency of 96.37% has been achieved from weight loss method at 60 °C. CMC/AgNPs is found to retard both the anodic and cathodic reactions and the adsorption is explained using Langmuir adsorption isotherm. AFM and SEM graphics reveal smoother surface for St37 sample in the acid solution containing inhibitor than inthe solution without the inhibiting agent. FTIR and EDS results show that CMC/AgNPs molecules were adsorbed on the metal surface.

Enhancement of Surface Coating Characteristics of Epoxy Resin by Dextran: An Electrochemical Approach

This work describes the use of polymer dextran to enhance the corrosion protection of epoxy coating applied on 6061 Al-15%(v) SiC(p) composite material (Al-CM). Initially, conditions were established to obtain optimum inhibition efficiency of dextran. Electrochemical techniques such as potentiodynamic polarization and electrochemical impedance spectroscopy were adopted for the corrosion rate measurements. Later, the same techniques were employed to study the corrosion rate of the epoxy resin coated composite material (EC-CM) before and after the addition of environmentally benign dextran polymer. Detailed investigation of the surface morphology of the coated Al-CM was carried out using scanning electron microscopy, energy dispersion X-ray analysis, and atomic force microscopy techniques. The work which is done with dual purpose, establishes not only the anticorrosive property of dextran, but also proves its ability to improve the coating characteristics of epoxy resin on Al-CM.

Corrosion inhibition studies of the combined admixture of 1, 3-diphenyl-2-thiourea and 4-hydroxy-3-methoxybenzaldehyde on mild steel in dilute acid media

La corrosión de acero dulce es responsable de pérdidas económicas e industriales debido a su deterioro acelerado. Los derivados sintetizados de tiourea y aldehídos fenólicos con heteroátomos inhiben la corrosión por adsorción sobre el acero mediante la formación de enlaces fuertes. Por tanto, se estudiaron las propiedades de inhibición de la corrosión electroquímica de la mezcla combinada de 1,3-difenil-2-tiourea y 4-hidroxi-3-metoxibenzaldehído sobre acero dulce en medios de H2SO4 y HCl 1 M mediante análisis de pérdida de peso, método de polarización potenciodinámica, microscopía óptica y espectroscopia IR. Los resultados mostraron que la mezcla inhibe eficazmente la corrosión del acero dulce en ambas soluciones con una eficacia de inhibición óptima de 97,4% y 97,47% en H2SO4, mientras que los valorescorrespondientes al HCl son 94,71% y 89,73%. Los cálculos termodinámicos demostraron que el compuesto quimiosorbido sobre la superficie de acero bloquea la difusión de aniones corrosivos. Las imágenes micro-analíticas confirmaron la efectiva propiedad de inhibición del compuesto y su presencia en la topografía superficial del acero. Los espectros infrarrojos revelaron la presencia de los grupos funcionales del compuesto orgánico responsable de la inhibición de la corrosión. La adsorción del compuesto se dedujo siguiendo las isotermas de adsorción de Langmuir, Frumkin y Freundlich.

Polypropylene glycol: A novel corrosion inhibitor for × 60 pipeline steel in 15% HCl solution

Polypropylene glycol (PPG) was investigated as a corrosion inhibitor for typical ×60 pipeline steel in 15% HCl solution using weight loss, electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation (EFM), linear polarization resistance (LPR) and potentiodynamic polarization (PDP) techniques. Water contact angle measurements and scanning electron microscopy (SEM) were employed for surface morphology characterization. Results obtained show that polypropylene glycol acts as a good corrosion inhibitor for ×60 pipeline steel in the strong acid environment. Inhibition efficiency increased with an increase in PPG concentration and temperature up to 55°C but decreased as immersion time was prolonged. Optimum inhibition efficiency of 90.5% was obtained at 55°C with 1000ppm PPG concentration from weight loss method. Potentiodynamic polarization studies revealed that PPG functions as a mixed-type inhibitor. The corrosion inhibition effect of PPG could be related to the adsorption of PPG molecules on the metal surface which follows Langmuir adsorption isotherm model and a protective film formation.

A Combined Inhibiting Effect of Sodium Alginate and Sodium Phosphate on the Corrosion of Magnesium Alloy AZ31 in NaCl Solution

The inhibiting effect of joint-addition of sodium alginate (SA) and sodium phosphate (SP) on corrosion of magnesium (Mg) alloy AZ31 (3 wt% aluminum and 1 wt% zinc) in 3.5 wt% NaCl solution was investigated by electrochemical impedance spectroscopy, potentiodynamic polarization analysis, mass loss measurements, and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). Results reveal a combined inhibiting effect derived from the presence of SA and SP with respect to Mg alloy AZ31 and an optimal inhibition efficiency in terms of corrosion of AZ31 substrate was yielded in 3.5 wt% NaCl electrolyte containing 0.05 wt% SA and 0.15 wt% SP. SEM-EDS examination suggested that such a promising combined inhibiting mechanism could be attributed to the formation of a compact, homogeneous and protective composite film. Chemical composition study through Fourier transform infrared spectroscopy elucidates that such a protective film contains not only conventional magnesium hydroxide as a result of corrosion of Mg alloy AZ31, but SA and SP through chemical adsorption on the surface of Mg alloy AZ31.

Synergized Plant Leave Extracts as Substitute to Toxic Additives in Alkyd Resin Primer for Corrosion Inhibition of Steel

Inhibition of steel corrosion by synergized leave extracts of Sida acuta and Jatropha curcas as additives substitute to synthetic compounds in Alkyd based Primer coats was investigated in 1.0 M HCl using the gasometric technique at 30°C and 50°C. Results obtained showed that the extract alternative effectively inhibited corrosion of degalvanised steel more than the synthetic chemical. This was confirmed by optimum inhibition efficiency of 93% to 90% corrosion rate 0.202 cm3/hr to 0.337 cm3/hr of the extract to the synthetic compound. Activation energy and Energy of adsorption decrease with time. Fourier transform infra red analysis confirmed the presence of C=O of ester by the presence of C-O functional band at 1094 cm-1. Surface morphology of the steel with the synergized were studied with Scanning electron microscope (SEM) and Electron dispersive X-ray spectroscopy (EDX) which revealed the protection of the internal grains of the metal from dissolution into corrodent provided by the adsorbed film the extract.

Inhibition and mechanism of Terminalia catappa on mild-steel corrosion in sulphuric-acid environment

Mild-steel samples were immersed in 0.5 M H2SO4 having different concentrations of Terminalia catappa leaf-extract for investigating inhibition and mechanism of the leaf-extract on mild-steel corrosion in the test-environment. Corrosion-rate measurements were obtained by potentiodynamic polarisation and gravimetric techniques and analysed for detailing sustainable corrosion-protection by the natural-plant in the test-environment. Results indicate potentiodynamic corrosion-rate correlated excellently (R = 99.25%, Nash-Sutcliffe efficiency (NSE) = 98.52%, ANOVA p-value = 0.0222) with function of the gravimetric corrosion-rate and the leaf-extract concentration. By the experimental and correlated results, inhibition effectiveness on mild-steel corrosion increased with increasing leaf-extract concentration up to the 8 g/L Terminalia catappa leaf-extract, which exhibited optimal inhibition efficiency, η = 99.99% (experimental model) or η = 95.45% (correlation prediction). Correlation prediction, potentiodynamic and gravimetric data followed the Langmuir and the Flory-Huggins adsorption isotherms with agreements of favourable adsorption/prevalent physisorption mechanism for the leaf-extract corrosion-protection of mild-steel in the test-environment.

Synergistic effect p-phenylenediamine and n,n diphenylthiourea on the electrochemical corrosion behaviour of mild steel in dilute acid media

Electrochemical studies of the synergistic effect of p-phenylenediamine and n,n diphenylthiourea (TPD) as corrosion inhibitor of mild steel in dilute sulphuric and hydrochloric acid through weight loss and potentiodynamic polarization at ambient temperature were performed. Experimental results showed the excellent performance of TPD with an optimal inhibition efficiency of 88.18 and 93.88 % in sulphuric and 87.42 and 87.15 % in hydrochloric acid from both tests at all concentration studied. Polarization studies show the compound to be a mixed-type inhibitor. Adsorption of deanol on the steel surface was observed to obey the Langmuir and Frumkin isotherm models. X-ray diffractometry confirmed the absence of corrosion products and complexes. Optical microscopy confirmed the selective inhibition property of TPD to be through chemical adsorption on the steel surface.

ELECTROCHEMICAL STUDY AND COMPUTATIONAL DETAILS OF COPPER CORROSION INHIBITION BY 1H-BENZOTRIAZOLE IN 3 wt. % NaCl MEDIUM

The effect of 1H-benzotriazole (BTAH) with ppm (part per million) grade concentrations on copper corrosion in aerated 3 wt. % NaCl solution is studied using chemical method (weight loss) and electrochemical methods (Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy (EIS)). The present study confirm that the BTAH acts as a mixed-type inhibitor of copper corrosion in 3 wt. % NaCl. The optimum inhibition efficiency is at 30 ppm of BTAH. The surface characterization is performed using Scanning Electron Microscopy (SEM) to confirm the adsorption of the inhibitor molecules after 21 days of immersion time in aerated 3 wt. % NaCl. The results obtained from different techniques used in this research are in very good agreement and revealed that the BTAH is a very good inhibitor of copper corrosion in sodium chloride medium. Computer Simulation techniques confirm that the BTAH molecules adsorbed on the Cu (110) Surface.

Corrosion inhibition of mild steel in hydrochloric acid using extract of glycine max leaves

The activity of glycine max leaves extract against corrosion of mild steel in 0.5 M HCl solution has been investigated at different temperatures (298–328 K). Different measurements were done using weight loss, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM)–energy dispersive x-ray spectroscopy (EDS) and X-ray diffraction (XRD) techniques. The weight loss results indicate that glycine max leaves extract is a good inhibitor and its optimum inhibition efficiency reaches up to 91.07 % at 2 g l−1 (308 K). The adsorption of the inhibitor molecules onto the mild steel surface was found to follow the Langmuir adsorption isotherm. The values of the Gibbs free energy of adsorption strongly support physisorption of inhibitor molecules on the mild steel surface. The decrease in inhibition efficiency is observed with increasing temperature, but increases with increase in inhibitor concentration. Formation of a protective layer against acid attack on the metal surface was confirmed by use of FT-IR, XRD analysis, and SEM.

Inhibition and compressive-strength performance of Na2Cr2O7and C10H14N2Na2O8·2H2O in steel-reinforced concrete in corrosive environments

This paper studied corrosion-inhibition and compressive-strength performances of Na2Cr2O7(sodium dichromate) and C10H14N2Na2O8·2H2O (ethylenediaminetetraacetic disodium salt: EDTA-Na2) admixtures in steel-reinforced concrete immersed in NaCl and in H2SO4corrosive environments. Electrochemical methods were used for studying corrosion responses of different concentrations of the individual admixtures and their synergies, in the model that partially replace the toxic Na2Cr2O7by the environmentally-friendly C10H14N2Na2O8·2H2O, in steel-reinforced concretes. After the electrochemical experiment, the steel-reinforced concrete samples were subjected to the compressive-strength testing and analyses of ASTM C39/C39M-03 and ASTM C267-01(2012). Results showed that the use of environmentally-friendly EDTA-Na2for partially replacing toxic Na2Cr2O7chemical exhibited better corrosion-inhibition and compressive-strength improvement in the NaCl-immersed concretes, than in the H2SO4-immersed concretes. The 2 g Na2Cr2O7+ 6 g EDTA-Na2admixture (representing partial replacement model of 6 g Na2Cr2O7by 6 g EDTA-Na2) exhibited optimal corrosion inhibition efficiency (η = 99.0%) and very good compressive-strength improvement advantage in the NaCl-immersed concretes. In contrast, comparatively low compressive-strength reduction trade-off with the good inhibition effectiveness of η = 79.9% support use of 6 g EDTA-Na2admixture only (i.e., without Na2Cr2O7addition) for inhibiting reinforcing-steel corrosion in the H2SO4-immersed concretes.

Effect of Adenine Concentration on the Corrosion Inhibition of Aisi 304l Steel in 1.0m Sulphuric Acid Solution

Over the years considerable efforts have been deployed to finding suitable (safe and friendly) corrosion inhibitors of organic origin in the various aggressive acid media encountered in service especially during the processes of pickling, industrial acid cleaning, acid descaling and oil well acidizing. In this research the effect of adenine concentration on the corrosion inhibition of AISI 304L in 1.0 M sulphuric acid solution has been investigated. The research was achieved by using 1M concentration of acid solution and varied inhibitor concentration. Readings were obtained every 240hours (10 days) for a period of 1200hours (50 days). Weight loss, corrosion penetration rate, inhibition efficiency and degree of surface coverage were calculated. Results obtained revealed that adenine is an effective and safe corrosion inhibitor for AISI 304L in 1.0M sulphuric acid solutions. Analysis of the results showed that the inhibition efficiency and surface coverage increases with increasing adenine concentration till a certain maximum value, causing a decrease in corrosion penetration rate and weight loss. A maximum value of inhibition efficiency of 89.56% was achieved at 0.011M adenine concentration after 10 days. This gave a surface coverage of 0.8956 and corrosion penetration rate of 0.022132mm/yr. Hence, the best adenine concentration for the corrosion inhibition of alloys 304L in 1.0M sulphuric acid solution to obtain optimum inhibition efficiency is 0.011M. Keywords: Corrosion, AISI 304L Steel, Inhibition efficiency, Degree of Surface coverage, 1.0M Sulphuric Acid Solution

Probability density fittings of corrosion test-data: Implications on C6H15NO3 effectiveness on concrete steel-rebar corrosion

In this study, corrosion test-data of steel-rebar in concrete were subjected to the fittings of the Normal, Gumbel and the Weibull probability distribution functions. This was done to investigate the suitability of the results of the fitted test-data, by these distributions, for modelling the effectiveness of C6H15NO3, triethanolamine (TEA), admixtures on the corrosion of steel-rebar in concrete in NaCl and in H2SO4 test-media. For this, six different concentrations of TEA were admixed in replicates of steel-reinforced concrete samples which were immersed in the saline/marine and the microbial/industrial simulating test-environments for seventy-five days. From these, distribution fittings of the non-destructive electrochemical measurements were subjected to the Kolmogorov–Smirnov goodness-of-fit statistics and to the analyses of variance modelling for studying test-data compatibility to the fittings and testing significance. Although all fittings of test-data followed similar trends of significant testing, the fittings of the corrosion rate test data followed the Weibull more than the Normal and the Gumbel distribution fittings, thus supporting use of the Weibull fittings for modelling effectiveness. The effectiveness models on rebar corrosion, based on these, identified 0.083% TEA with optimal inhibition efficiency, η = 72.17± 10.68%, in NaCl medium while 0.667% TEA was the only admixture with positive effectiveness, η = 56.45±15.85%, in H2SO4 medium. These results bear implications on the concentrations of TEA for effective corrosion protection of concrete steel-rebar in saline/marine and in industrial/microbial environments.

Electrochemical Performance of Anthocleista djalonensis on Steel-Reinforcement Corrosion in Concrete Immersed in Saline/Marine Simulating-Environment

In this paper, electrochemical techniques were employed to study performance of different concentrations of Anthocleista djalonensis leaf-extract admixtures on the corrosion of steel-reinforcement in concrete immersed in 3.5 % NaCl, for simulating saline/marine environment. Analysed test-results showed that the corrosion rate correlated directly with admixture concentration and inversely with cube of the ratio of standard deviations of corrosion potential and corrosion current. The 0.4167 % A. djalonensis (per weight of cement) exhibited optimal inhibition efficiency, η = 97.43 ± 1.20 %, from analysed experimental data, or 94.80 ± 3.39 %, from predicted correlation model, on steel-reinforcement corrosion in the medium. The other admixture concentrations also exhibited high efficiencies at inhibiting steel-reinforcement corrosion in the chloride contaminated environment. Isotherm fittings of the experimental and predicted performance suggest that they both obeyed the Langmuir adsorption model. Evaluated parameters from the isotherm model indicated favourable adsorption and predominant chemisorption mechanism by this environmentally-friendly inhibitor of steel-reinforcement corrosion in the saline/marine simulating-environment.

Rhizophora Mangle L. Effects on Steel-reinforced Concrete in 0.5 M H2SO4: Implications for Corrosion-degradation of Wind-energy Structures in Industrial Environments

This paper studies corrosion inhibition and compressive-strength effect of Rhizophora mangle L. leaf-extract on steel-reinforced concrete in 0.5M H2SO4, simulating industrial environment of wind-energy installations. Electrochemical monitoring and load- bearing/compressive-strength testing were employed for different concentrations of the leaf-extract admixed in duplicated samples of steel-reinforced concretes, immersed in the test-system. Analyses of the experimental test-results, as per ASTM G16- 95 R04, identified 0.1667% Rhizophora mangle L., per weight of cement, with optimum (very good) inhibition efficiency. Rhizophora mangle L. admixtures combined good inhibition efficiency with compressive-strength improvements in concretes. These bear implications for protecting wind-energy structures against corrosion-degradation in industrial environments.

Effects of the downregulation of SnoN expression on HepG2 cell proliferation and apoptosis

Ski‑novel protein (SnoN) is a proto‑oncogene that belongs to the Ski protein family and is involved in regulating processes such as cell proliferation and apoptosis. To investigate the role of SnoN in the proliferation and apoptosis of HepG2 cells, we downregulated its expression by the use of small interfering RNA (siRNA). Three fragments predicted to have RNAi capacity were designed and synthesized as the target siRNAs (siRNA‑A, ‑B and ‑C). Following transfection, inhibition efficiency was detected by reverse transcription PCR (RT‑PCR) and western blot analysis. The siRNA with the optimal inhibition efficiency was used for the cell proliferation and apoptosis analysis. Cell proliferation was analyzed by the Cell Counting Kit‑8 (CCK‑8) and cell apoptosis was investigated by flow cytometry. In our study, all three siRNAs efficiently inhibited SnoN expression, and siRNA‑C demonstrated the optimal inhibition efficiency. We found that following downregulation of SnoN expression, HepG2 cell proliferation was significantly inhibited (P<0.05), while HepG2 cell apoptosis was significantly increased (P<0.05). SnoN‑specific siRNA is capable of effectively inhibiting the expression of SnoN in human HepG2 cells, and the downregulation of SnoN expression induces growth inhibition and apoptosis.

Inhibitive Action of Ferrous Gluconate on Aluminum Alloy in Saline Environment

The corrosion of aluminum in saline environment in the presence of ferrous gluconate was studied using weight loss and linear polarization methods. The corrosion rates were studied in different concentrations of ferrous gluconate 0.5, 1.0, 1.5, and 2.0 g/mL at 28°C. Experimental results revealed that ferrous gluconate in saline environment reduced the corrosion rate of aluminum alloy at the different concentrations studied. The minimum inhibition efficiency was obtained at 1.5 g/mL concentration of inhibitor while the optimum inhibition efficiency was achieved with 1.0 g/mL inhibitor concentration. The results showed that adsorption of ferrous gluconate on the aluminium alloy surface fits Langmuir adsorption isotherm. The potentiodynamic polarization results showed that ferrous gluconate is a mixed type inhibitor. Ferrous gluconate acted as an effective inhibitor for aluminium alloy within the temperature and concentration range studied. The data obtained from weight loss and potentiodynamic polarization methods were in good agreement.

Anti‐corrosion properties of bis(benzimidazole) derivatives for N80 steel in H2S solution

In this work, we systematically investigated the effect of four bis(benzimidazole) derivatives containing different heteroatoms in molecular structures on inhibiting corrosion of N80 steel in 0.5 mmol·l−1 H2S solution by potentiodynamic polarization, electrochemical impedance spectroscopy and metallographic microscope. The results showed that within the range of 0.1–1.0 mmol·l−1, the adsorption of bis(benzimidazole) derivatives on N80 steel surface was found to follow Langmuir adsorption isotherm. Meanwhile, stable adsorbing monolayer between inhibitors and the metal surface was formed, which was confirmed by thermodynamic adsorption parameters (Kads, ). This series of bis(benzimidazole) derivatives exhibited obvious corrosion inhibitory properties for N80 steel. Moreover, they could both slow down the anodic dissolution of iron and the cathodic reduction reaction as mixed type corrosion inhibitors. The optimal inhibition efficiency was obtained for 1,3‐bis(benzimidazl‐2‐yl)‐2‐thiapropane (BBMS). Hopefully, this series of inhibitors might find applications in anti‐corrosion and many other areas. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Synergistic Inhibition Effect of Sodium Silicte and Phytic Acid for Carbon Steel in Neutral Salt Water

The inhibition effects of sodium silicate, phytic acid and their mixtures in 5% NaCl solutions have been investigated using weight loss method and Tafel polarization techniques. The surface morphology of carbon steel was obtained using scanning electron microscopy (SEM). The results show that the co-addition of 70 mg∙1-1 sodium silicate and 5 g∙1-1 phytic acid has the optimum inhibition efficiency (84.15%) and the lowest corrosion rate (0.13 g∙m-2∙h-1). Compared with their individual inhibition effects, the optimum inhibition efficiency of sodium silicate is 62.17% at 90 mg∙1-1 and phytic acid is 80.05% at 15 g∙1-1, respectively. The results obtained from weight loss method and Tafel polarization curves are in good agreement. The results show the enhanced inhibition effect by the inhibitors mixtures.