This document summarizes a study on the corrosion inhibition of carbon steel in hydrochloric acid using an aqueous extract of Neem leaves grown in the United Arab Emirates. Electrochemical and weight loss experiments were conducted to evaluate the inhibition effectiveness of the Neem extract at temperatures ranging from 303 to 343 K. The results showed that the Neem extract was an effective corrosion inhibitor for carbon steel in HCl solution, with inhibition effectiveness increasing with higher extract concentrations and decreasing with higher temperatures. The inhibition was attributed to compounds in the Neem leaves such as tannins and triterpene glycosides that can adsorb onto the steel surface.
Investigative studies on the inhibitive effects of Newbouldialaevis extracts ...researchinventy
The inhibitive effects ofNewbouldiaLaevis (NL) leaf extract and magnetic field on copper corrosion in 0.5M H2SO4 aqueous solution were investigated experimentally by gravimetric technique and theoretically using Quantum Chemical calculations. The results show that both NL and the magnetic field caused reduction in corrosion rate. The inhibition efficiency increased with concentration. The magnetic field caused greater increase in the inhibition efficiency. Temperature increase caused a decrease in inhibition efficiency. The activation energy is low and oscillates, possibly due to error factor from non-linearity of the Arrhenius plot. Among the tested isotherms, Langmuir has the highest correlation coefficient of 0.9963 and 0.7935 with and without magnet field respectively. The magnetic field increased the change in free energy, caused the reaction to become spontaneous, one mole of the inhibitor to replace 4 moles of water mole while reducing the number of monolayer of the inhibitor on the metal. The quantum chemical calculations performed on newbouldiaquinone and lapacholconstituents of NL showed that lapachol contributed more to the inhibition efficiency due its low binding energy, high dipole moment, chemical softness and fractional electron transfer. The magnetic field and temperature played opposite roles.
The corrosion protection of mild steel in 1 M H3PO4 solution by apricot juice was studied
at different temperatures by weight loss technique. Adsorption, activation and statistical studies
were addressed in this work. Adsorption studies showed that inhibitor adsorbed on metal surface
according to Langmuir isotherm. Average value of heat of adsorption was 14.93 kJ/mol indicates
a spontaneous physical adsorption on metal surface. Activation parameters did not changed with
addition of inhibitor indicates that there is no change in reaction mechanism. Analysis of variance
(ANOVA) was also applied. This analysis showed that the corrosion rate influenced by temperature,
inhibitor concentration and combined interaction of them.
Ginger extract as corrosion inhibitor from natural resources was studied to prevent corrosion of mild steel in acid media. Ginger rhizome was extracted to produce green corrosion inhibitor (G-1) while ginger powder bought at supermarket was also extracted to form a green corrosion inhibitor (G-2). Effectiveness of inhibitor in preventing corrosion process of mild steel was studied in 1.0 M of hydrochloric acid
Effect of plant extracts on corrosion rate of mild steel in acidic mediumPremier Publishers
2.5ml Ethanol is used on plant extracts of locus bean (parkiabiglobosa) and banana sap (musaparadisiaca) as corrosion inhibitors for mild steel in 1M dilute HCl was investigated using weight loss techniques. Corrosion tests were first carried out for 1 and 3 hrs of immersion time respectively at various concentrations of extracts (0.5ml, 1.0ml, 1.5ml, 2.0ml and 2.5ml) and 2.5ml were used as corrosion inhibitors and at different temperatures (38oC, 45oC and 55oC). Results showed that the minimum corrosion rate obtained for 1 hr at 38oC with extract of Pakiabiglobosa is 0.85×10-4g/cm3/min and efficiency of 18.75% for 1hr, while at 55oC the corrosion rate was 4.37×10-4 g/cm3/min and efficiency of 33%. With ethanol extract of banana sap, minimum corrosion rate and efficiency recorded at 38°C were (4.16×10-4 g/cm3/min and efficiency of (22.1%), while at 55oC they were (0.83×10-4 g/cm3/min) and (7.6%) respectively. From these results, it is concluded that extracts of locust bean and banana sap can be successfully used as corrosion inhibitors in specified acidic medium.
A Study of the Corrosion Inhibition of Mild Steel in 0.5M Tetraoxosulphate (V...IJAEMSJORNAL
A comparative study of the corrosion inhibition performance of Alstonia boonei leaves extract in 0.5M tetraoxosulphate (VI) acid at different temperatures (30ᵒC, 50ᵒC and 70ᵒC) was undertaken. The results showed that Alstonia boonei leaves extract was more efficient as a corrosion inhibitor at 30ᵒC compared to temperatures of 50ᵒC and 70ᵒC.The adsorption of Alstonia boonei leaves extract was found to obey Langmuir adsorption isotherm at all temperatures (30ᵒC, 50ᵒC and 70ᵒC), but did not obey Freundlich adsorption isotherm at all temperatures. A study of the effect of temperature on corrosion rate and inhibition efficiency showed that corrosion rate increased with increase in temperature, while the inhibition efficiency decreased with increase in temperature.
Corrosion Inhibition of Mild Steel in HCl Medium by a Condensation Productijtsrd
A condensation product CP was successfully synthesized from reaction of dimethyl amino benzaldehyde and aniline giving yields of 80 . The compound was characterized by Fourier Transform Infrared FTIR Spectroscopy. The corrosion inhibiting property of the CP on mild steel in HCl solution were investigated by the weight loss measurements, electrochemical impedance spectroscopy EIS and linear polarization resistance LPR . The concentrations of CP were varied from 1 x 10 3 M to 5 x 10 3 M. The inhibition efficiencies obtained from all the methods employed were in good agreement where the percentage of inhibition efficiencies increased with concentration of CP. Results showed that CP was the better inhibitor with inhibition efficiency of 90 at 5 x 10 3 M additive concentration. This is likely due to the effect of its large molecular size, higher number of electroactive heteroatoms and bigger p electron cloud of the conjugated double bond system. Ganesha Achary "Corrosion Inhibition of Mild Steel in HCl Medium by a Condensation Product" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-4 , June 2020, URL: https://www.ijtsrd.com/papers/ijtsrd30869.pdf Paper Url :https://www.ijtsrd.com/chemistry/physical-chemistry/30869/corrosion-inhibition-of-mild-steel-in-hcl-medium-by-a-condensation-product/ganesha-achary
Red Dragon Fruit (Selenicereus costaricensis) Waste Peels as Corrosion Inhibi...Innspub Net
Metal corrosion is brought about by the oxidation of atoms on the surface, resulting in irreversible damage to structures at staggering costs. Hence, the search for efficient and cost-effective corrosion inhibitors is relevant. Waste agricultural by-products which have no food or economic value serve as good potential sources for these environmentally benign corrosion inhibitors. Ethanolic extracts of Red Dragon Fruit (RDF) have been previously reported to contain high amounts of flavonoids and polyphenols, which can manifest inhibitory activity against corrosion brought about by aggressive electrolytes. In this study, the ethanolic extract of Selenicereus costaricensis waste peels was tested for its anti-corrosion property using weight loss method. We have also probed its performance as a potential corrosion inhibitor at a range of different temperatures from 303 to 343 K. The calculated inhibition efficiency of 2% RDF was 97%. Thermodynamic studies reveal that increasing inhibitor concentration raises the activation parameters of mild steel in an acidic medium such as activation energy (Ea) and changes in enthalpy (DHo) and entropy (DSo). It was found that the corrosion inhibition process using RDF waste peel extract mainly occurs under diffusion control. Moreover, increased immersion time, inhibitor concentration, and temperature led to increased inhibition efficiency. The spontaneous process (DGoads = -23.47 kJ/mol) of adsorption of RDF on mild steel surfaces obeys the Langmuir isotherm model.
Investigative studies on the inhibitive effects of Newbouldialaevis extracts ...researchinventy
The inhibitive effects ofNewbouldiaLaevis (NL) leaf extract and magnetic field on copper corrosion in 0.5M H2SO4 aqueous solution were investigated experimentally by gravimetric technique and theoretically using Quantum Chemical calculations. The results show that both NL and the magnetic field caused reduction in corrosion rate. The inhibition efficiency increased with concentration. The magnetic field caused greater increase in the inhibition efficiency. Temperature increase caused a decrease in inhibition efficiency. The activation energy is low and oscillates, possibly due to error factor from non-linearity of the Arrhenius plot. Among the tested isotherms, Langmuir has the highest correlation coefficient of 0.9963 and 0.7935 with and without magnet field respectively. The magnetic field increased the change in free energy, caused the reaction to become spontaneous, one mole of the inhibitor to replace 4 moles of water mole while reducing the number of monolayer of the inhibitor on the metal. The quantum chemical calculations performed on newbouldiaquinone and lapacholconstituents of NL showed that lapachol contributed more to the inhibition efficiency due its low binding energy, high dipole moment, chemical softness and fractional electron transfer. The magnetic field and temperature played opposite roles.
The corrosion protection of mild steel in 1 M H3PO4 solution by apricot juice was studied
at different temperatures by weight loss technique. Adsorption, activation and statistical studies
were addressed in this work. Adsorption studies showed that inhibitor adsorbed on metal surface
according to Langmuir isotherm. Average value of heat of adsorption was 14.93 kJ/mol indicates
a spontaneous physical adsorption on metal surface. Activation parameters did not changed with
addition of inhibitor indicates that there is no change in reaction mechanism. Analysis of variance
(ANOVA) was also applied. This analysis showed that the corrosion rate influenced by temperature,
inhibitor concentration and combined interaction of them.
Ginger extract as corrosion inhibitor from natural resources was studied to prevent corrosion of mild steel in acid media. Ginger rhizome was extracted to produce green corrosion inhibitor (G-1) while ginger powder bought at supermarket was also extracted to form a green corrosion inhibitor (G-2). Effectiveness of inhibitor in preventing corrosion process of mild steel was studied in 1.0 M of hydrochloric acid
Effect of plant extracts on corrosion rate of mild steel in acidic mediumPremier Publishers
2.5ml Ethanol is used on plant extracts of locus bean (parkiabiglobosa) and banana sap (musaparadisiaca) as corrosion inhibitors for mild steel in 1M dilute HCl was investigated using weight loss techniques. Corrosion tests were first carried out for 1 and 3 hrs of immersion time respectively at various concentrations of extracts (0.5ml, 1.0ml, 1.5ml, 2.0ml and 2.5ml) and 2.5ml were used as corrosion inhibitors and at different temperatures (38oC, 45oC and 55oC). Results showed that the minimum corrosion rate obtained for 1 hr at 38oC with extract of Pakiabiglobosa is 0.85×10-4g/cm3/min and efficiency of 18.75% for 1hr, while at 55oC the corrosion rate was 4.37×10-4 g/cm3/min and efficiency of 33%. With ethanol extract of banana sap, minimum corrosion rate and efficiency recorded at 38°C were (4.16×10-4 g/cm3/min and efficiency of (22.1%), while at 55oC they were (0.83×10-4 g/cm3/min) and (7.6%) respectively. From these results, it is concluded that extracts of locust bean and banana sap can be successfully used as corrosion inhibitors in specified acidic medium.
A Study of the Corrosion Inhibition of Mild Steel in 0.5M Tetraoxosulphate (V...IJAEMSJORNAL
A comparative study of the corrosion inhibition performance of Alstonia boonei leaves extract in 0.5M tetraoxosulphate (VI) acid at different temperatures (30ᵒC, 50ᵒC and 70ᵒC) was undertaken. The results showed that Alstonia boonei leaves extract was more efficient as a corrosion inhibitor at 30ᵒC compared to temperatures of 50ᵒC and 70ᵒC.The adsorption of Alstonia boonei leaves extract was found to obey Langmuir adsorption isotherm at all temperatures (30ᵒC, 50ᵒC and 70ᵒC), but did not obey Freundlich adsorption isotherm at all temperatures. A study of the effect of temperature on corrosion rate and inhibition efficiency showed that corrosion rate increased with increase in temperature, while the inhibition efficiency decreased with increase in temperature.
Corrosion Inhibition of Mild Steel in HCl Medium by a Condensation Productijtsrd
A condensation product CP was successfully synthesized from reaction of dimethyl amino benzaldehyde and aniline giving yields of 80 . The compound was characterized by Fourier Transform Infrared FTIR Spectroscopy. The corrosion inhibiting property of the CP on mild steel in HCl solution were investigated by the weight loss measurements, electrochemical impedance spectroscopy EIS and linear polarization resistance LPR . The concentrations of CP were varied from 1 x 10 3 M to 5 x 10 3 M. The inhibition efficiencies obtained from all the methods employed were in good agreement where the percentage of inhibition efficiencies increased with concentration of CP. Results showed that CP was the better inhibitor with inhibition efficiency of 90 at 5 x 10 3 M additive concentration. This is likely due to the effect of its large molecular size, higher number of electroactive heteroatoms and bigger p electron cloud of the conjugated double bond system. Ganesha Achary "Corrosion Inhibition of Mild Steel in HCl Medium by a Condensation Product" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-4 , June 2020, URL: https://www.ijtsrd.com/papers/ijtsrd30869.pdf Paper Url :https://www.ijtsrd.com/chemistry/physical-chemistry/30869/corrosion-inhibition-of-mild-steel-in-hcl-medium-by-a-condensation-product/ganesha-achary
Red Dragon Fruit (Selenicereus costaricensis) Waste Peels as Corrosion Inhibi...Innspub Net
Metal corrosion is brought about by the oxidation of atoms on the surface, resulting in irreversible damage to structures at staggering costs. Hence, the search for efficient and cost-effective corrosion inhibitors is relevant. Waste agricultural by-products which have no food or economic value serve as good potential sources for these environmentally benign corrosion inhibitors. Ethanolic extracts of Red Dragon Fruit (RDF) have been previously reported to contain high amounts of flavonoids and polyphenols, which can manifest inhibitory activity against corrosion brought about by aggressive electrolytes. In this study, the ethanolic extract of Selenicereus costaricensis waste peels was tested for its anti-corrosion property using weight loss method. We have also probed its performance as a potential corrosion inhibitor at a range of different temperatures from 303 to 343 K. The calculated inhibition efficiency of 2% RDF was 97%. Thermodynamic studies reveal that increasing inhibitor concentration raises the activation parameters of mild steel in an acidic medium such as activation energy (Ea) and changes in enthalpy (DHo) and entropy (DSo). It was found that the corrosion inhibition process using RDF waste peel extract mainly occurs under diffusion control. Moreover, increased immersion time, inhibitor concentration, and temperature led to increased inhibition efficiency. The spontaneous process (DGoads = -23.47 kJ/mol) of adsorption of RDF on mild steel surfaces obeys the Langmuir isotherm model.
Corrosion Inhibition of Carbon Steel in Chloride and Sulfate SolutionsIJERA Editor
Corrosion is a major problem in industry and in infrastructure; a huge sum of expenditure every year is spent on
preventing, retarding, and repairing its damages. This work studies the engineering of an inhibitor for carbon
steel metal used in the cooling systems containing high concentration of chloride and sulfate ions. For this
purpose, the synergy between the dichromate, molybdate and nitrite inhibitors is examined and optimized to the
best results. Moreover, care was taken that the proposed inhibitor is compliant with the environmental laws and
regulations.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
The effect of ethanol extract of leaves of Conyza Dicorides plant on the corrosion inhibition
of mild steel in 1M HCl solution was investigated by weight loss and electrochemical polarization
techniques at temperature range (25–65 ̊C). The Results obtained showed that the percentage
inhibition efficiency increases with the increasing of inhibitor concentration and decreases with the
increasing of temperature. At a concentration of 2 g/L, the percentage inhibition efficiency reached
about (94.87%) at 25 ̊C. The thermodynamic activation functions of dissolution process and
adsorption parameters were calculated and discussed. Adsorption of the additive was found to follow
the Langmuir adsorption isotherm.
A new technique to measure oxygen reduction kinetics underneath coatings using hydrogen permeation from the back side. Huge step towards characterising buried interface reactivity.
Hydroxyl capped silver-gold alloy nanoparticles: characterization and their c...Nanomedicine Journal (NMJ)
Objective(s):
Metal nanoparticles (NPs) offer a wide variety of potential applications in pharmaceutical sciences due to the unique advances in nanotechnology research. In this work, bimetal Ag-Au alloy NPs were prepared and their combinations with other antibiotics were tested against Staphylococcus aureus.
Materials and Methods:
Firstly, Ag-Au alloy NPs with Au/Ag molar ratio of 1:1 was fabricated and was purified by agarose gel electrophoresis system. The morphology and size of the purified NPs were confirmed by transmission electron microscopy. Chemical composition and surface chemistry of these NPs were studied with atomic absorption spectophotometry and Fourier transforms infrared spectroscopy, respectively. The size of purified Ag-Au alloy NPs was less than 200 nm. Also the presence of organic compounds with a hydroxyl residue was detected on the surface of these purified NPs. In next step the effect of purified Ag-Au alloy NPs on the antibacterial activity of different antibiotics was evaluated at sub-inhibitory content (5 μg/disk) using disk diffusion method against S. aureus. Ag NPs and Au NPs were also tested at same content (5 μg) using mentioned method.
Results:
The most enhancing effect of Ag-Au alloy NPs was observed for penicillin G and piperacillin. No enhancing effects on the antibacterial activity of different antibiotics were observed at 5 μg/disk for the mono-metal nanoparticles (Ag NPs and Au NPs) against S. aureus.
Conclusion:
These results signify that the Ag-Au alloy NPs potentiates the antimicrobial action of certain antibiotics suggesting a possible utilization of this nano material in combination therapy against resistant S. aureus.
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
Processing of Lignin and the Removal of Detrimentals with Deep Eutectic SolventsEuropeanPaper
By Laura Kollau, Dannie van Osch & Panos Kourios, PhD Students from TU Eindhoven. This was presented during the Two Team Project - Winners' first successes session, organised as part of European Paper Week 2015. More at http://www.cepi.org/epw
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Corrosion Inhibition of Carbon Steel in Chloride and Sulfate SolutionsIJERA Editor
Corrosion is a major problem in industry and in infrastructure; a huge sum of expenditure every year is spent on
preventing, retarding, and repairing its damages. This work studies the engineering of an inhibitor for carbon
steel metal used in the cooling systems containing high concentration of chloride and sulfate ions. For this
purpose, the synergy between the dichromate, molybdate and nitrite inhibitors is examined and optimized to the
best results. Moreover, care was taken that the proposed inhibitor is compliant with the environmental laws and
regulations.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
The effect of ethanol extract of leaves of Conyza Dicorides plant on the corrosion inhibition
of mild steel in 1M HCl solution was investigated by weight loss and electrochemical polarization
techniques at temperature range (25–65 ̊C). The Results obtained showed that the percentage
inhibition efficiency increases with the increasing of inhibitor concentration and decreases with the
increasing of temperature. At a concentration of 2 g/L, the percentage inhibition efficiency reached
about (94.87%) at 25 ̊C. The thermodynamic activation functions of dissolution process and
adsorption parameters were calculated and discussed. Adsorption of the additive was found to follow
the Langmuir adsorption isotherm.
A new technique to measure oxygen reduction kinetics underneath coatings using hydrogen permeation from the back side. Huge step towards characterising buried interface reactivity.
Hydroxyl capped silver-gold alloy nanoparticles: characterization and their c...Nanomedicine Journal (NMJ)
Objective(s):
Metal nanoparticles (NPs) offer a wide variety of potential applications in pharmaceutical sciences due to the unique advances in nanotechnology research. In this work, bimetal Ag-Au alloy NPs were prepared and their combinations with other antibiotics were tested against Staphylococcus aureus.
Materials and Methods:
Firstly, Ag-Au alloy NPs with Au/Ag molar ratio of 1:1 was fabricated and was purified by agarose gel electrophoresis system. The morphology and size of the purified NPs were confirmed by transmission electron microscopy. Chemical composition and surface chemistry of these NPs were studied with atomic absorption spectophotometry and Fourier transforms infrared spectroscopy, respectively. The size of purified Ag-Au alloy NPs was less than 200 nm. Also the presence of organic compounds with a hydroxyl residue was detected on the surface of these purified NPs. In next step the effect of purified Ag-Au alloy NPs on the antibacterial activity of different antibiotics was evaluated at sub-inhibitory content (5 μg/disk) using disk diffusion method against S. aureus. Ag NPs and Au NPs were also tested at same content (5 μg) using mentioned method.
Results:
The most enhancing effect of Ag-Au alloy NPs was observed for penicillin G and piperacillin. No enhancing effects on the antibacterial activity of different antibiotics were observed at 5 μg/disk for the mono-metal nanoparticles (Ag NPs and Au NPs) against S. aureus.
Conclusion:
These results signify that the Ag-Au alloy NPs potentiates the antimicrobial action of certain antibiotics suggesting a possible utilization of this nano material in combination therapy against resistant S. aureus.
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
Processing of Lignin and the Removal of Detrimentals with Deep Eutectic SolventsEuropeanPaper
By Laura Kollau, Dannie van Osch & Panos Kourios, PhD Students from TU Eindhoven. This was presented during the Two Team Project - Winners' first successes session, organised as part of European Paper Week 2015. More at http://www.cepi.org/epw
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
The Genetic Background of Chemical Communication and Chemosensory Gene Evolut...Katri Ketola
The genetic background of chemical communication and chemosensory gene evolution in ants. Master's thesis project.
Darwinian selection can be measured and investigated from gene sequences. A certain gene form favored by positive selection will become more common in the population. Detecting strong positive selection is rare, but it has been found to affect genes involved in immune defense and perception of odorants. Genes under positive selection have a possible role in speciation or adaptation. This is why chemical communication, being based on the sense of smell, is an interesting topic for measuring natural selection and positive selection in particular. Social insects, such as ants, are model organisms for chemical communication. They use chemical communication not only for finding nutrition and detecting intruders, but also in coordinating the activities of several thousands of colony members.
Corrosion of mild steel in HCl was investigated using the weight loss method. The
mild steel used was cut into 16 coupons with 5.0 cm x 5.0 cm x 0.2 cm dimensions
which were degreased with ethanol and washed with distilled water and finally
weighed. The mild steel coupons were exposed to HCl with varied concentrations (0,
10, 25 and 40%) of Garcinia kola extracts used as corrosion inhibitors for 4 hours at
400C and 600C respectively. The result showed that at 400C; the inhibition efficiency
of 65.5% was observed at 25 % HCl concentration and 62.9% at 40% HCl
concentration while at 600C; inhibition efficiency of 87.7% was at 25% HCl
concentration and 88.1% at 40% concentration respectively. It can be concluded that
increase in concentration increases the inhibition efficiency. The presence of
flavonoid and alkanoids in bitter kola stem is a good inhibitor.
Thermodynamic characterization of metal dissolution and inhibitor adsorption ...IJRES Journal
The inhibition effect of 1-hexyl-3-methylimidazolium chloride (HMIC) on the corrosion of mild
steel in 2M sulphuric acid solution has been investigated by weight loss. potentiodynamic polarization and
electrochemical impedance spectroscopy. The effect of temperature on the corrosion behavior of mild steel in
2M H2SO4 with addition of inhibitor was studied in weight loss method at the temperature range of 308-328 K.
Results obtained that the inhibition efficiency increases with increasing the concentration of the inhibitor and
decreases with increasing the temperature. Polarization and impedance measurements were in good agreement.
The adsorption of this inhibitor on the mild steel surface obeys the Langmuir adsorption isotherm. Fourier
transform spectroscopy (FTIR) and Scanning electron microscopy (SEM) was also carried out to establish the
corrosion inhibit property of this inhibitor in sulphuric acid medium. Quantum chemical calculations were
performed using density functional theory to find out whether a clear link exists between the inhibitive effect of
the inhibitor and the electronic properties of its main constituents.
Corrosion Behaviour of 6061 Al-SiC Composites in KOH MediumEditor IJCATR
The present research work deals with the corrosion behaviour of 6061 Al-15% (vol) SiC(P) composites. The addition of the
reinforcement like SiC to Aluminium has been reported to decrease the corrosion resistance of the matrix due to several reasons, one
of them being galvanic action between the reinforcement and the matrix. In the present work, the corrosion behaviour of 6061 Al-15%
(vol) SiC(P) composites in KOH at different concentration (0.5M, 1M, 1.5M) and different temperature (300C, 350C, 400C, 450C, 500C)
was determined by Tafel extrapolation technique. The inhibition action of 8-Hydroxyquinoline on corrosion behaviour of 6061 Al-
15% (vol) SiC(P) composites in KOH at different concentration of inhibitor (200ppm, 400ppm); different concentration of medium
(0.5M, 1M,1.5M) and different temperature (300C, 350C, 400C, 450C, 500C) was investigated. The results indicate that corrosion rate
of Al-SiC composite in KOH increases as the concentration of medium increases and also as temperature of medium increases. The
results indicate that the inhibitor is moderately effective in inhibiting the corrosion of 6061 Al-15% (vol) SiC(P) composites. As the
inhibitor concentration increases, the corrosion rate decreases. The surface morphology of the metal surface was investigated using
scanning electron microscope (SEM). Activation energy was evaluated using Arrhenius equation, and enthalpy of activation and
entropy of activation values were calculated using transition state equation
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Experimental and Quantum Chemical Studies on the Corrosion Inhibition Perform...inventionjournals
Corrosion inhibition nature of a synthesized Schiff’s base was studied on the corrosion of mild steel in 1.0 M HCl using weight loss and electrochemical methods. The results indicated that the synthesized Schiff base is an effective inhibitor in reducing the corrosion of mild steel in 1.0 M HCl solution. The inhibitor efficiency of inhibitor increased with inhibitor concentration and showed maximum inhibition efficiency at 300 ppm concentration. The adsorption of inhibitor molecules on to the metal surface obeyed Langmuir Adsorption isotherm. The adsorption mechanism involved both physical and chemical adsorptions. The potentiodynamic polarization studies showed that the inhibitor is a mixed typed inhibitor with more cathodic nature. Potential of zero charge was also determined and the adsorption mechanism discussed. Quantum mechanical studies showed that the Schiff base molecules have the strong tendency to donate electron pairs to the metallic atoms on the surface
Some factors affecting on the behavior ofsteel electrode in citric acid solut...IJERA Editor
Potential-time curves are constructed for the steel electrode in naturally aerated citric acid solutions devoid of
and containing some aggressive and inhibitive compounds. Cl- and SO4
2- ions cause the destruction of passivity
and initiation of pitting corrosion. The rate of oxide film growth by citric acid and oxide film destruction by Cl-
and SO4
2- ions follows a direct logarithmic law as evident from the linear relationships between the open-circuit
potential and the logarithm of immersion time. Urea, phenylhydrazine and 1,2-phenylenediamine compounds
inhibit the pitting corrosion of steel. The rate of oxide film healing and thickening increases with their
concentrations. In presence of constant inhibitor concentration, the efficiency of pitting inhibition increases in
the order: (weak) urea<phenylhydrazine><1,2-phenylenediamine(strong).
Effect of Inhibitor Concentration and Immersion Time on the Corrosion Rate an...AJSERJournal
The effect of inhibitor concentration and immersion time on the corrosion rate and inhibition efficiency of
AISI 1019 steel in seawater environment were investigated by means of weight loss measurement (WLM) at an interval
of 6days for a period of 60 days. AISI 1019 steel were immersed in seawater solution in the absence and presence of
varying inhibitor concentrations of potassium chromate (PC), Sodium Nitrite(SN), Methyl Orange (MO), Methyl Red
(MR), Terminalia Catappa Leaves (TCL) Extract, Carica papaya Leaves (CPL) Extract. The results showed that there is an
increase in inhibition efficiency with increase in inhibitor concentration and decrease in inhibition efficiency with
increase in immersion time. The inorganic inhibitor (potassium chromate), inorganic inhibitor (Sodium Nitrite), the
organic Inhibitor (Methyl Orange), the organic inhibitor (Methyl Red), the green inhibitor (Terminalia Catappa Leaves)
and green inhibitor (Carica Papaya Leaves) produced their best inhibition efficiency of 71.94%, 634%, 68.94%, 68.32%,
627% ,59.79% respectively at a concentration of 10g/L. From the result obtained, the potassium chromate inhibitor has
better inhibitory property than other inhibitors, which revealed that it is best suited for inhibition of corrosion of mild
steel in seawater environment.
Inhibition of Sulphuric Acid Corrosion of Mild Steel by Surfactant and Its Ad...IOSR Journals
Abstract: The corrosion inhibition effect of surfactant, N,N-Dimethyl-N-(2-Phenoxyethyl)dodecan-1- aminiumbromide(DPDAB) on mild steel corrosion in 0.5M Sulphuric acid was investigated by weight loss, potentiodynamic polarization and Electrochemical impedance spectroscopic techniques. DPDAB is an excellent inhibitor and its inhibition efficiency increases with increase in concentration and maximum inhibition efficiency was observed above the critical micelle concentration (CMC). The polarization curves reveal that DPDAB acts as mixed type inhibitor with predominantly of anodic type. The corrosion inhibition efficiency of DPDAB increases with increase in concentration and decreases with increase in temperature from 298K to 308K and then increases and shows maxima at 318K and then decreases at 328K.. The adsorption of the inhibitor on the mild steel in 0.5M H2SO4 was found to obey Langmuir’s adsorption isotherm. Scanning electronic microscopy (SEM) confirmed the existence of an adsorbed protective film on the metal surface. The kinetic and thermodynamic parameters were calculated and discussed.
Hydrogen Gas Production from Tannery Wastewater by Electrocoagulation of a Co...IOSRJAC
The performance of a continuous electrocoagulation (EC) process was investigated for tannery wastewater treatment using aluminum and iron electrodes. The effects of the operating parameters, such as current density, pH of solution and inlet flow rate, on pollutants removal efficiency and recovery of hydrogen gas were investigated in order to optimize process performance. In the case of aluminum electrodes, The results showed that for tannery wastewater with an influent pH adjusted at about 6, the use of a current density of 14 mA/cm2 , and an EC time of 125 min, gave access to pollutants (COD, Color, Cr, and NH3-N) removal efficiency 73, 94, 100 and 51%, respectively. The energy yield of harvested hydrogen was 16% of the electrical energy demand of the electrocoagulation process. However, in the case of iron electrodes, with effluent pH adjusted at about 7, , the use of a current density of 14 mA/cm2 , and an EC time of 125 min, gave access to pollutants (COD, Color, Cr, and NH3-N) removal efficiency 67, 93, 100 and 46 %, respectively. And also, the energy yield of harvested hydrogen was 15 % of the electrical energy demand of the electrocoagulation process. Thus, the operating costs for two cases were found to be 0.675 $/m3 wastewater. It could be seen that hydrogen gas production coupled with pollutants removal efficiency by EC continuous mode would be an effective approach for energy recovery and wastewater reutilization.
2. 2 International Journal of Corrosion
Table 1: The effect of soaking time of Neem leaves in distilled water
on the percentage inhibition.
Time of soaking neem
leaves in water (hours)
Inhibition at 303 K(%)
0.17 50
0.33 55
0.5 60
1 70
3 77
7 80
14 80
24 80
168 80
Several extraction procedures were tested. These extrac-
tion procedures included extraction by distilled water at
80◦
C, extraction by distilled water at room temperature, and
extraction by boiling ethanol (78◦
C). Preliminary corrosion
studies by weight-loss measurements were carried out in
order to find the optimal extraction procedure. These pre-
liminary corrosion measurements showed that the aqueous
extraction at room temperature was the same or far more
efficient than the two other procedures. This extraction
procedure was adopted in our current work.
In order to optimize the time of extraction of the
Neem, 2.0 g of the dry Neem leaves were soaked in 60 mL
distilled water at room temperature (20◦
C) for various time
ranging from 0.17 hours to 168 hours, followed by filtration,
then added to an aqueous HCl solution to make a 1.0 L
solution in 1.0 M HCl. Weight-loss measurements described
in (Section 2.2.3) were carried out on steel specimens
prepared as shown in (Section 2.2.1) in each extract solution.
The percent inhibition was finally calculated according to
(2). It was found that 7 hours was the optimal soaking time
as shown in Table 1 and Figure 1.
In this work, 2.0 g of dry Neem leaves were soaked in
60.0 mL distilled water at room temperature (20◦
C) for 7
hours (the optimal time), and then filtered. The filtrate
was added to an aqueous HCl solution to make a 1.0 L
stock solution in 1.0 M HCl. From the stock solution, a
series of diluted solutions in 1.0 M HCl were prepared with
concentrations ranging from 2.0 g/L to 0.02 g/L.
2.1. Electrochemistry
2.1.1. Electrode Preparation. 5 mm diameter working elec-
trode was prepared from a 5 mm diameter carbon steel
rod (IS 226 containing 0.18% C, 0.6% Mn, and 0.35%
Si) supplied by “Reliable Steel Traders”, Sharjah, UAE;
and mounted, using Araldite epoxy resin, in a glass tube
that fits in the electrochemical cell. The working carbon
steel electrode was abraded using a series of carborundum
papers starting with 600 grades and ending with 1200
grades prior to each experiment. The electrode surface was
then polished with 0.3 μm alumina on cloth, washed with
deionized distilled water, and rinsed with pure ethanol before
100
90
80
70
60
50
40
1E−01 1E+00 1E+01 1E+02
Inhibition(%)
1E+03
Time of soaking Neem leaves in water (hr)
Figure 1: The effect of soaking time of Neem leaves in distilled
water on the percentage inhibition.
1
9
2
5
8 10
6
3
4
7
Figure 2: The electrochemical cell. (1) gas bubbler, (2) B 12 glass
socket, (3) Platinum gauze (counter electrode), (4) glass frit, (5)
inlet for nitrogen gas, (6) luggin capillary (reference electrode), (7)
steel rod (working electrode), (8) epoxy resin, (9) B 24 glass socket,
(10) copper wire.
it was transferred to the electrochemical cell that contained
deaerated fresh electrolyte.
2.1.2. Instrumentation. The same electrochemical glass cell
(made in Southampton University, England) used in our
previous works [8–13] and described in Figure 2 was here
employed. The electrochemical cell consisted of a carbon
steel working electrode (WE), a saturated calomel electrode
3. International Journal of Corrosion 3
(SCE) as a reference electrode (RE), and platinum gauze
counter electrode (CE). Prior to each experiment, the elec-
trolyte was deaerated by nitrogen bubbling. The cell design
allowed nitrogen to escape into the solution, precluding its
collection at the electrode surface that is fitted horizontally.
The counter-electrode compartment was separated from
the working-electrode compartment with a glass frit. This
way, the working electrode was protected from any substance
that may be produced at the counter electrode during the
electrochemical reactions. The electrochemical equipment
and chemicals used were as follows.
A PC-controlled Sycopel AEW2-1000 electrochemical
workstation (supplied from Sycopel Scientific Limited, Eng-
land) capable of driving currents up to ±1 A with an output
potential across the cell of up to ±10 V.
Analytical-grade hydrochloric acid (Ajax) was used.
2.1.3. Measuring Procedure. Electrochemical corrosion mea-
surements (Tafel plots) were carried out on the carbon steel
electrode, prepared as described above, in 1.0 M HCl and in
1.0 M HCl containing various concentrations of the aqueous
Neem extract. The concentration of the Neem extract ranged
from 2.0 g/L to 0.2 g/L.
60 milliliters of the freshly prepared electrolyte was filled
in the electrochemical cell. The solution was then deaerated
with nitrogen gas; and the working electrode equilibrium
potential versus SCE was recorded until it reached a steady
state. Finally, the electrode potential was scanned from
−700 mV to −100 mV versus SCE at a sweep rate of
1 mV·s−1. The data were collected and plotted as logarithm
of the absolute value of the current (log |I|, mA) versus
the electrode potential (E, mV) versus SCE. With extreme
experimental precautions taken, and with a newly polished
electrode and fresh electrolyte, the experiment was repeated
for at least three times in order to ensure the reproducibility
of the results. Once reproducible plots were obtained, the
corrosion currents were then extrapolated from the log |I|
(logarithm of current, mA) versus electrode potential plots
(Tafel plots).
2.2. Effect of Temperature
2.2.1. Specimen Preparation. Rectangular specimens (1cm ×
2.3cm × 0.3cm) were cut from a 3 mm thick carbon steel
sheet (IS 226 containing 0.18% C, 0.6% Mn, and 0.35% Si)
supplied by “Reliable Steel Traders”, Sharjah, UAE; and used
in the weight loss measurements. Close to the upper edge of
the specimen, a 2 mm diameter hole was drilled and served
to be hooked with a glass rod for immersion purposes. The
specimens were polished with 600 grade emery paper, rinsed
with distilled water, degreased with acetone, dried, and
finally weighed precisely on an accurate analytical balance
prior to each experiment.
2.2.2. Instrumentation. For the weight-loss measurements
[14, 15], a 250 mL round bottom flask fitted with a reflux
condenser and long glass rod which served to hook and
immerse the specimen and in turn immersed in a thermally
controlled water bath was used.
−4
−3
−2
−1
0
1
2
−0.7 −0.6 −0.5 −0.4 −0.3
1
2
3
4
5
LogI(mA)
Potential E (V) versus SCE
Figure 3: Anodic and cathodic polarization curves of carbon steel
in an uninhibited 1.0 M HCl solution and in 1.0 M HCl containing
various concentrations of the aqueous extract of Neem leaves.(1)
1.0 M HCl; (2) 1.0 M HCl + 0.20 g/L extract; (3) 1.0 M HCl +
0.50 g/L extract; (4) 1.0 M HCl + 1.00 g/L extract; (5) 1.0 M HCl
+ 2.00 g/L extract.
2.2.3. Measuring Procedure. 100 mL of 1.0 M HCl solution
either with or without the presence of various concentrations
of aqueous Neem extract were transferred in the flask. The
flask was then placed in water bath. When the required
temperature was reached, the precisely weighed carbon steel
specimen hooked with a glass rod was immersed in the
solution for exactly six hours. After that time, the sample was
removed, rinsed with distilled deionized water, degreased
with acetone, dried, and finally weighed precisely on an
accurate analytical balance. This procedure was repeated for
a variety of inhibitor concentrations ranging from 0.02 g/L to
2.00 g/L; and at temperatures ranging from 303 K to 343 K.
3. Results and Discussion
3.1. Electrochemistry. The anodic and cathodic polarization
curves (Tafel plot) of the carbon steel electrode in deaerated
1.0 M HCl solution with and without the addition of
various concentrations of the aqueous Neem extract are
shown in Figure 3. The aqueous Neem extract acted as a
mixed inhibitor because its presence at all concentrations
affected both, the anodic and the cathodic branches of the
polarization curves. Furthermore, the polarization curves
corresponding to all concentrations of the aqueous Neem
extract were all almost at equal distance from that recorded
with uninhibited 1.0 M HCl. The corrosion current of carbon
steel electrode in each solution was determined by locating
the intersections of extrapolated tangents of the anodic and
cathodic curves of the Tafel plot at the corrosion potential
(Erest). Values of associated electrochemical parameters and
corresponding percent inhibition are given in Table 2. The
corrosion current was found to decrease with the increase of
the concentration of the inhibitor as shown in Table 2. In the
absence of inhibitor (1.0 M HCl), the corrosion current was
4. 4 International Journal of Corrosion
Table 2: Tafel corrosion currents and percentage inhibitions of the aqueous extract of Neem leaves at various concentrations in 1.0 M HCl
at room temperature.
1.0 M HCl
1.0 M HCl +
0.20 g/LExtract
of Neem
1.0 M HCl +
0.50 g/LExtract
of Neem
1.0 M HCl +
1.00 g/LExtract
of Neem
1.0 M HCl +
2.00 g/LExtract
of Neem
Erest/V versus SCE −0.465 −0.438 −0.433 −0.472 −0.583
ba/(mV/dec.) 57.5 61.1 94.5 112.0 143.9
ba/(mV/dec.) 63.8 56.1 87.7 77.2 76.1
I“corrosion”/mA 0.76 0.237 0.169 0.151 0.101
PercentInhibition — 68.82 77.76 80.13 86.84
0
20
40
60
80
100
1E−01 1E+00 1E+01
Inhibitor concentration (g/L)
Inhibition(%)
Figure 4: Percentage inhibition of different concentrations of the
aqueous extract of Neem leaves on carbon steel surface in 1.0 M
HCl solution at room temperature based on anodic and cathodic
polarization curves.
0.76 mA; and dropped to 0.101 mA when the concentration
of aqueous Neem leaves extract reached 2.0 g/L in 1.0 M HCl
(Table 2).
The values of percentage inhibition of aqueous Neem
extract at various concentrations in 1.0 M HCl were calcu-
lated according to (1), and are shown in Table 2:
Percentage Inhibition =
(ICorr.)Uninh. − (ICorr.)Inh.
(ICorr.)Uninh.
× 100,
(1)
where (ICorr.)Uninh. = Corrosion current in the uninhibited
solution, and (ICorr.)Inh. = Corrosion current in inhibited
solution.
The plot of the percentage inhibition versus the concen-
tration of the aqueous Neem extract in 1.0 M HCl is shown
in Figure 4. This figure shows that the percentage inhibition
has steeply increased from about 69% with 0.20 g/L inhibitor
to about 87% with 2.0 g/L inhibitor.
There are many factors affecting the corrosion inhibition
efficiency by organic compounds such as the number and
types of adsorbing groups as well as their molecular size,
molecular structure, and mode of interaction with the
corroding metal surface. These molecules have the ability to
inhibit corrosion either by chemisorption or physisorption
on the metal surface. The molecules that physisorbed reduce
corrosion by shifting the cathodic reaction at the sides where
they attached, while the chemisorbed ones that attached
at the anodic areas retard the reactivity of these areas
towards corrosion. Neem is bitter in taste due to the high
content of tannins and a series of complex compounds
called “triterpenes” or more specifically “limonoids”. One
of the most important triterpenes is azadirachtin. Nearly
100 protolimonoids, limonoids or tetranortriterpenoids,
pentanortriterpenoids, exanortriterpenoids, and some pon-
terpenoid constituents have been isolated from various parts
of the Neem tree; still more are being isolated. As tannins
contain polyphenolic moieties and these moieties have the
ability to form tanninate salts with ferric ions, the corrosion
inhibition of tannins is due to the formation of a highly
cross-lined network of ferric tanninate salts that protect
the metal surface. In the same way, triterpenes have some
functional groups such as (OH, C = O, C = C) that can
interact with the metal surface and protect it from the attack
of hydronium (H3O+) ions.
When the electrode was pulled out from the 1.0 M HCl
containing an aqueous extract of 2.0 g/L of Neem leaves (at
the end of the experiment), the carbon steel surface was more
clean (about 87% inhibition) compared with the experiment
with concentration of 0.20 g/L in 1.0 M HCl (about 69%
inhibition).
The high inhibition efficiency may be attributed to the
presence of tannins, triterpenes, and many other organic
compounds that have been extracted by only soaking the dry
Neem leaves in distilled water.
3.2. Effect of Temperature
Weight-loss corrosion tests were carried out on the carbon
steel immersed in 1.0 M HCl in the absence or presence
of aqueous Neem extract over a period of 6 hours. Table 3
represents the corrosion rate [mg·cm−2·h−1] and the per-
centage efficiency for Neem inhibitor with concentrations
varying from 0.02 g/L to 2.00 g/L at 303, 313, 323, 333, and
5. International Journal of Corrosion 5
Table 3: The Effect of concentration of the aqueous extract of Neem leaves on the corrosion rate (mg·cm−2·h−1) and percentage efficiency
of carbon steel in 1.0 M HCl at various temperatures.
Temperaure e/K
343 333 323 313 303
Concentration
of Inhibitor
% Efficieny Corr. Rate % Efficieny Corr. Rate % Efficieny Corr. Rate % Efficieny Corr. Rate Corr. Rate % Efficieny
1.0 M HCl 0.961 — 1.394 — 4.671 — 12.225 — 26.280 —
1.0 M HCl +
0.02 g/L
0.548 43 0.920 34 3.643 22 11.247 8 32.324 −23
1.0 M HCl +
0.20 g/L
0.336 65 0.600 57 2.989 36 11.003 10 31.010 −18
1.0 M HCl +
0.50 g/L
0.250 74 0.544 61 2.382 49 9.169 25 27.594 −5
1.0 M HCl +
1.00 g/L
0.221 77 0.516 63 2.055 56 7.964 35 25.229 4
1.0 M HCl +
2.00 g/L
0.192 80 0.446 68 1.822 61 7.335 40 24.178 8
303K
313K
323K
0
1
2
3
4
1E−02 1E−01 1E+00 1E+01
Concentration (g/L)
Corrosionrate(mg·cm−2·h−1)
0.5
1.5
2.5
3.5
Figure 5: Effect of concentration of the aqueous extract of Neem
leaves on the corrosion rate (mg·cm−2·h−1) of carbon steel in 1.0 M
HCl at various temperatures.
343 K, respectively. The percentage efficiency was calculated
according to (2):
%Inhibition =
WUninh. − WInh.
WUninh.
× 100, (2)
where WUninh. = corrosion rate without inhibitor; and
WInh. = corrosion rate with inhibitor.
The corrosion rate of the carbon steel in 1.0 M HCl as
a function of various concentrations of aqueous extract of
Neem leaves at temperatures between 303 and 343 K were
333K
343K
0
5
10
15
20
25
30
35
1E−02 1E−01 1E+00 1E+01
Concentration (g/L)
Corrosionrate(mg·cm−2·h−1)
Figure 6: Effect of concentration of the aqueous extract of Neem
leaves on the corrosion rate (mg·cm−2·h−1) of carbon steel in 1.0 M
HCl at various temperatures.
shown in Figures 5 and 6. It was obviously noticed that the
corrosion rate dropped rapidly at lower concentrations of
the extract Neem than at higher ones at 303 K and 313 K,
while the situation was the opposite at 323 K and 333 K. At
343 K, there was no inhibition at all at low concentrations
and instead, acceleration in the rate of corrosion was noticed.
This could be due to the presence of the ions in the Neem
leaves extract (extracted with water), and because at this
elevated temperature the adsorption of the inhibitor (at low
concentration) was low, the dissolved ions had high influence
on the increase of the corrosion rate in addition to the HCl
6. 6 International Journal of Corrosion
Table 4: The data obtained from the weight loss measurements for Arrhenius Equation: (I/T) against Ln (Corrosion Rate).
Ln (Corrosion Rate)/mg·cm−2·h−1
(1/T) × 103/K−1 1.0 M HCl 1.0 M HCl+ 0.02 g/L 1.0M HCl+ 0.20 g/L 1.0 M HCl+ 0.50 g/L 1.0 M HCl+ 1.00 g/L 1.0 M HCl+ 2.00 g/L
3.30 −0.03978 −0.60148 −1.09064 −1.38629 −1.50959 −1.65026
3.19 0.33218 −0.08338 −0.51083 −0.59059 −0.66165 −0.80744
3.10 1.54137 1.29281 1.09494 0.86794 0.72028 0.59993
3.00 2.50348 2.4201 2.39817 2.21583 2.07493 1.99266
2.92 3.26881 3.47581 3.43431 3.3176 3.22799 3.18544
303K
313K
323K
333K
343K
−30
−10
10
30
50
70
90
1E−02 1E−01 1E+00 1E+01
Inhibitor concentration (g/L)
Inhibition(%)
Figure 7: Effect of concentration of the aqueous extract of Neem
leaves on the percent inhibition of carbon steel in 1.0 M HCl at
various temperatures.
solution. When the concentration of the extract increased,
more inhibitor seemed to get adsorbed on the metal surface,
which in turn caused less effect of dissolved ions on the
corrosion rate.
The relative decrease in the corrosion rate was more sig-
nificant at lower temperatures than at higher ones as shown
in Figures 5 and 6. This means that the rate of corrosion
decreased more significantly at lower temperatures.
The plots of the percentage inhibition as a function of
the concentration of the aqueous extract of Neem leaves
at temperatures ranging from 303 K to 343 K were shown
in Figure 7. Similar to the rate of corrosion in Figures 5
and 6, the inhibition was so obvious and more effective at
low temperatures than at higher ones, and even a catalysis
effect (negative inhibition values) was noticed at 343 K and
concentrations of equal or less than 0.50 g/L.
According to Arrhenius Equation (3), the values of
natural logarithms of the rate of corrosion (ln Rate of
corrosion) and the values of the reciprocal of the temperature
0.5g/L
1g/L
2g/L0.2g/L
0.02g/L
1M HCl
−3
−2
−1
0
1
2
3
4
2.8 3 3.2 3.4
1/T ×103 (K−1)
Lncorrosionrate(mg·cm−2·h−1)
Figure 8: The Arrhenius plots of the corrosion rate of carbon steel
in 1.0 M HCl solution with and without the presence of various
concentrations of the aqueous extract of Neem leaves.
in K−1 (1/T) were tabulated in Table 4:
ln rate = −
Ea
RT
+ constant, (3)
where Ea = activation energy [kcal·mol−1], R = gas constant
[kcal·mol−1], T = absolute temperature [K], and const. =
constant
The Arrhenius plots of the corrosion of carbon steel in
1.0 M HCl solution, (ln corrosion rate as a function of 1/T)
with or without the presence of the aqueous extract of Neem
leaves at concentrations ranging from 0.02 g/L to 2.0 g/L are
plotted in Figure 8. From this figure, the slope (−Ea/R) of
each line was determined and used to calculate the activation
energy according to (3), with R = 1.987 × 10−3
kcal·mol−1.
It is clearly noticed that as the concentration of the extract
increases, the activation energy for the corrosion of carbon
steel in 1.0 M HCl is also increase (18.27 kcal·mol−1in 1.0 M
HCl without inhibitor to 25.96 kcal·mol−1with an aqueous
extract of Neem leaves of 2.0 g/L in 1.0 M HCl), (Table 5).
The values of the surface coverage of various concentra-
tions of the aqueous Neem leaves extract (from 0.02 g/L to
2.0 g/L) on carbon steel surface at various temperatures are
7. International Journal of Corrosion 7
Table 5: The activation energy (Ea) for the corrosion of carbon steel
in 1.0 M HCl with and without the aqueous extract of Neem leaves
at various concentrations.
System
Activation Energy, Ea (kcal·mol−1)
2.00 g/L 1.00 g/L 0.50 g/L 0.20 g/L 0.02 g/L
1.0 M HCl 18.27 18.27 18.27 18.27 18.27
1.0 M HCl +
The Aqueous
Extract of
Neem Leaves
25.96 25.42 25.43 24.88 22.15
303K
313K
323K
333K
343K
0
0.2
0.4
0.6
0.8
1
−5 −4 −3 −2 −1 0 1 2
Ln concentration (g/L)
Surfacecoverage
−0.4
−0.2
Figure 9: Effect of concentration of the aqueous extract of Neem
leaves on the surface coverage of carbon steel in 1.0 M HCl at
various temperatures.
tabulated in Table 6. These values were extracted from the
corresponding percentage efficiency values reported earlier
in Table 3. The plot of the values of surface coverage, θ,
against the natural logarithm of the concentration of Neem
leaves aqueous extract; ln C, for carbon steel at various
inhibitor temperatures is shown in Figure 9. After examin-
ing these data and adjusting them to different theoretical
adsorption isotherms, it was concluded that the inhibitor was
adsorbed on the carbon steel surface according to Temkin
Adsorption Isotherm:
−2aθ = ln KC, (4)
where a = molecular interaction constant, θ = degree of
coverage, K = equilibrium constant for the adsorption
reaction, and C = concentration of the inhibitor.
The equilibrium constant for the adsorption reaction, K,
is related to the standard free energy of adsorption via (5)
[16]:
K =
1
55.5
exp −
ΔG
RT
, (5)
Where: K = equilibrium constant for the adsorption reac-
tion, 55.5 = concentration of water [mol·L−1], ΔG = standard
free energy [kcal·mol−1], R = gas constant [kcal·mol−1], and
T = absolute temperature [K].
According to (4), the straight lines shown in Figure 9 will
have the following slopes and intercepts:
Slope = −
1
2a
, (6)
Intercept = −
1
2a
lnK. (7)
Combination of (6) and (7) leads to the following
relationships:
Intercept = Slope (ln K), (8)
K = e (Intercept/Slope)
. (9)
Using (9), the equilibrium constant for the adsorption
reaction, K, was calculated.
The free energy of adsorption of the inhibitor, ΔG, was
calculated using (5) at various temperatures (303 K to 343 K)
as shown in Table 7.
The enthalpy of adsorption, ΔH, for the inhibitor was
calculated from the following and is shown in Table 8:
ΔH = Ea − RT. (10)
The entropy, ΔS, was calculated at various temperatures for
the inhibitor using the following and is shown in Table 9:
ΔG = ΔH − TΔS. (11)
The activation energy (Ea) for the corrosion of carbon
steel in the presence of the aqueous extract of neem
leaves at all concentrations (0.02 g/L to 2.0 g/L) are higher
compared to the activation energy in the absence of the
extract (25.96 kcal·mol−1 with the extract of 2.0 g/L in 1.0 M
HCl compared with 18.27 kcal·mol−1 in 1.0 M HCl without
extract). This can be attributed to the fact that higher values
of Ea in the presence of inhibitor compared to its absence are
generally consistent with a physisorption, while unchanged
or lower values of Ea in inhibited solution suggest charge
sharing or transfer from the organic inhibitor to the metal
surface to form coordinate covalent bonds (chemisorption).
The increase in the activation energies for the corrosion
is attributed to a decrease in the adsorption of the inhibitor
on the metal surface as the temperature increased, and
subsequently, an increase in the corrosion rate will result due
to the greater exposed area of the metal surface to the acid. At
temperatures as high as 343 K and concentrations of extract
equal or lower than 0.50 g/L an acceleration of corrosion of
carbon steel was occurred.
The thermodynamic data obtained in the presence of
the Neem extract at various temperatures were tabulated
in Tables 7 to 9. These thermodynamic quantities represent
the algebraic sum of the values for adsorption and desorp-
tion. The negative value of ΔG indicates the spontaneous
adsorption of inhibitor on the surface of the carbon steel.
8. 8 International Journal of Corrosion
Table 6: The Effect of concentration of the aqueous extract of Neem leaves on surface coverage for carbon steel in 1.0 M HCl at various
temperatures.
Temperature/K
303 313 323 333 343
Concentration
of Inhibitor
Surface Coverage θ Surface Coverage θ Surface Coverage θ Surface Coverage θ Surface Coverage θ
1.0 M HCl +
0.02 g/L
0.43 0.34 0.22 0.08 −0.23
1.0 M HCl +
0.20 g/L
0.65 0.57 0.36 0.10 −0.18
1.0 M HCl +
0.50 g/L
0.74 0.61 0.49 0.25 −0.05
1.0 M HCl +
1.00 g/L
0.77 0.63 0.56 0.35 0.04
1.0 M HCl +
2.00 g/L
0.80 0.68 0.61 0.40 0.08
Table 7: The Free energy of adsorption (ΔGads) for carbon steel in
1.0 M HCl in the presence of the aqueous extract of Neem leaves at
various temperatures (303 K−343 K).
ΔG, kcal·mol−1
303 K 313 K 323 K 333 K 343 K
−8.01 −8.04 −6.58 −5.52 −2.84
Table 8: The enthalpy of adsorption (ΔH) for carbon steel in 1.0 M
HCl in the presence of the aqueous extract of (2.0 g/L) Neem leaves
at various temperatures (303 K−343 K).
ΔH, kcal·mol−1
303 K 313 K 323 K 333 K 343 K
25.36 25.34 25.32 25.30 25.28
Table 9: The change in entropy (ΔS) for carbon steel in 1.0 M HCl
in the presence of the aqueous extract of (2.0 g/L) Neem leaves at
various temperatures (303 K−343 K).
ΔS, kcal·K−1·mol−1
303 K 313 K 323 K 333 K 343 K
0.110 0.107 0.0988 0.0926 0.0820
The free energy, ΔG, increases from about −8 kcal·mol−1
at 303 K to about −3 kcal·mol−1 at 343 K. The adsorption
process is believed to be exothermic and associated with a
decrease in entropy (ΔS) of solute, while the opposite is true
for the solvent [17]. The gain in entropy which accompanies
the substitutional adsorption process is attributed to the
increase in the solvent entropy (Table 9). This agrees with
the general suggestion that the absolute values of free energy,
|ΔG|, increase with the increase of inhibition efficiency [18–
20] as the adsorption of organic compound is accompanied
by desorption of water molecules off the surface.
The high inhibition efficiency may be attributed to the
presence of tannins, triterpenes, and many other organic
compounds that have been extracted by only soaking the
dry Neem leaves in distilled water. This inhibition may be
also due to synergistic interactions between the adsorbed
compounds.
These results agree with Fouda et al. [21, 22] who sug-
gested that the inhibition efficiency of organic compounds
depends on many factors including their charge density,
number of adsorption sites, heat of hydrogenation, mode of
interaction with the metal surface, and formation of metallic
complexes.
4. Conclusions
The aqueous Neem leaves extract was found to be a highly
efficient inhibitor for carbon steel in 1.0 M HCl solution,
reaching about 87% at 2.0 g/L and room temperature, a
concentration considered to be very moderate. Even at one
half of this of this concentration, 1.0 g/L, an inhibition of
about 80% was obtained at room temperature.
The rate of corrosion of the carbon steel in 1.0 M HCl
is a function of the concentration of the neem extract. This
rate decreased as the concentration of the Neem extract is
increased.
The percentage of inhibition in the presence of this
inhibitor was decreased with temperature which indicates
that physical adsorption was the predominant inhibition
mechanism because the quantity of adsorbed inhibitor
decreases with increasing temperature.
The aqueous Neem leaves extract is an excellent, green,
eco-friendly, and very cheap corrosion inhibitor for carbon
steel in 1.0 M HCl solution, so it can be used to replace toxic
and highly cost chemicals.
Acknowledgments
The authors would like to thank the “College of Graduate
Studies and Research” at the University of Sharjah for
financially supporting this research project as well as their
research group entitled: “Corrosion Prevention & Control.”
9. International Journal of Corrosion 9
References
[1] H. Al-Sehaibani, “Evaluation of extracts of Henna leaves
as environmentally friendly corrosion inhibitors for metals,”
Materialwissenschaft und Werkstofftechnik, vol. 31, no. 12, pp.
1060–1063, 2000.
[2] M. Kliˇski´c, J. Radoˇsevi´c, S. Gudi´c, and V. Katalini´c, “Aqueous
extract of Rosmarinus officinalis L. as inhibitor of Al-Mg
alloy corrosion in chloride solution,” Journal of Applied
Electrochemistry, vol. 30, no. 7, pp. 823–830, 2000.
[3] P. C. Okafor and E. E. Ebenso, “Inhibitive action of Carica
papaya extracts on the corrosion of mild steel in acidic
media and their adsorption characteristics,” Pigment and Resin
Technology, vol. 36, no. 3, pp. 134–140, 2007.
[4] I. H. Farooqi, A. Hussain, M. A. Quraishi, and P. A. Saini,
“Study of low cost eco-friendly compounds as corrosion
inhibitors for cooling systems,” Anti-Corrosion Methods and
Materials, vol. 46, no. 5, pp. 328–331, 1999.
[5] H. H. Rehan, “Corrosion control by water-soluble extracts
from leaves of economic plants,” Materialwissenschaft und
Werkstofftechnik, vol. 34, no. 2, pp. 232–237, 2003.
[6] K. O. Orubite and N. C. Oforka, “Inhibition of the corrosion
of mild steel in hydrochloric acid solutions by the extracts of
leaves of Nypa fruticans Wurmb,” Materials Letters, vol. 58, no.
11, pp. 1768–1772, 2004.
[7] P. B. Raja and M. G. Sethuraman, “Atropine sulphate as
corrosion inhibitor for mild steel in sulphuric acid medium,”
Materials Letters, vol. 62, no. 10-11, pp. 1602–1604, 2008.
[8] A. Nahl´e and F. C. Walsh, “Electrochemical studies of two cor-
rosion inhibitors for iron in HCl: cetyltrimethyl ammonium
bromide and tetraphenyl phosphonium chloride,” Corrosion
Prevention and Control, vol. 42, no. 2, pp. 30–34, 1995.
[9] A. H. Nahl´e, “Electrochemical studies of corrosion inhibition
of a series of quaternary ammonium salts on iron in HCl
solution,” Corrosion Prevention and Control, vol. 44, no. 4, pp.
99–105, 1997.
[10] A. H. Nahl´e, “Inhibition of iron in HCl using benzyl trimethyl-
and triethyl-ammonium chlorides,” Corrosion Prevention and
Control, vol. 45, no. 4, pp. 124–130, 1998.
[11] A. Nahl´e, “Effect of triethanolamine on the electrochemical
dissolution of solder in NaOH solution,” Bulletin of Electro-
chemistry, vol. 18, no. 3, pp. 105–110, 2002.
[12] A. Nahl´e, I. Abu-Abdoun, and I. Abdel-Rahman, “Electro-
chemical studies of the effect of trans-4-hydroxy-4’-stilbazole
on the corrosion inhibition of mild steel in HCl solution,”
Anti-Corrosion Methods and Materials, vol. 54, no. 4, pp. 244–
248, 2007.
[13] A. Nahl´e, I. Abu-Abdoun, and I. Abdel-Rahman, “Corrosion
inhibition of (Anthraquinone-2-ylmethyl) triphenyl phos-
phonium bromide on mild steel in HCl solution,” Bulletin of
Electrochemistry, vol. 23, pp. 201–209, 2007.
[14] A. Nahl´e, “Effect of temperature on the corrosion inhibition
of carbon steel in HCl solutions,” Bulletin of Electrochemistry,
vol. 17, no. 5, pp. 221–226, 2001.
[15] A. Nahl´e, “Inhibition of corrosion of iron in HCl solution
by semicarbazides and thiosemicarbazides,” Bulletin of Electro-
chemistry, vol. 21, no. 6, pp. 275–281, 2005.
[16] B. B. Damaskin, O. A. Pietrij, and W. W. Batrokov, Adsorpcja
Organiczeskich Sojedinienij na elektrodach, Moskva, Russia,
1968.
[17] S. H. Sanad, A. A. Ismail, and A. A. El-Meligi, “The effect
of temperature on the corrosion and corrosion inhibition
of steel alloys in hydrochloric acid solutions,” Bulletin of
Electrochemistry, vol. 11, no. 10, pp. 462–469, 1995.
[18] B. G. Ateya, B. E. El-Anadouli, and F. M. El-Nizamy, “The
effect of thiourea on the corrosion kinetics of mild steel in
H2SO4,” Corrosion Science, vol. 24, no. 6, pp. 497–507, 1984.
[19] B. G. Ateya, B. E. El-Anadouli, and F. M. El-Nizamy, “The
adsorption of thiourea on mild steel,” Corrosion Science, vol.
24, no. 6, pp. 509–515, 1984.
[20] J. D. Talati, M. N. Desai, and N. K. Shah, “Meta-Substituted
aniline-N-salicylidenes as corrosion inhibitors of zinc in
sulphuric acid,” Materials Chemistry and Physics, vol. 93, no.
1, pp. 54–64, 2005.
[21] A. S. Fouda, M. N. Mousa, F. I. Taha, and A. I. Elneamaa, “The
role of some thiosemicarbazide derivatives in the corrosion
inhibition of aluminum in HCl,” Corrosion Science, vol. 26, no.
9, pp. 719–729, 1986.
[22] A. S. Fouda, A. Abd El-Aal, and A. B. Kandil, “The effect of
some phthalimide derivatives on the corrosion behaviour of
copper in nitric acid,” Anti-Corrosion Methods and Materials,
vol. 52, no. 2, pp. 96–101, 2005.