This document discusses the corrosion inhibition properties of di(Resacetophenone) 1,2 cyclohexandiimine (R DACH) Schiff base on steel in 1 M HCl solution. Electrochemical measurements including potentiodynamic polarization, electrochemical impedance spectroscopy, and chronoamperometry were used to evaluate the inhibition efficiency of R DACH at different concentrations and temperatures. The results showed that R DACH is an effective corrosion inhibitor for steel, with inhibition efficiency increasing with increasing concentration. Adsorption of the inhibitor followed the Langmuir isotherm. Activation energy and thermodynamic parameters like enthalpy, entropy, and Gibbs free energy of adsorption were calculated from corrosion currents at different temperatures and
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.
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
Inhibition, kinetic and thermodynamic effects of new Azo derivatives on iron ...Al Baha University
This investigation is designed to apply an advanced kinetic-thermodynamic model on the experimental data obtained from acidic and alkaline corrosion of iron using mono- and bis-azo dyes as corrosion inhibitors. The inhibition properties of the tested azo dyes on corrosion of iron in HNO3 and NaOH media were analyzed by gravimetric, thermometric and polarization measurements. The three studied methods gave consistent results. Polarization study showed that all the inhibitors are mixed type in acidic, act mainly as cathodic in alkaline solution. The synthesized azo dye derivatives exhibit good inhibition properties, obeys the Frumkin adsorption isotherm. The large values of the change in the standard free energy of adsorption (∆Goads), equilibrium constant (Kads) and binding constant (Kb) revealed that the reactions proceed spontaneously and result in highly efficient physisorption mechanism and stronger electrical interaction between the double layer existing at the phase boundary and the adsorbing molecules. The inhibition efficiency depends on the number of adsorption oxygen sites (OH and OMe groups), their charge density and π-electron clouds. The inhibition efficiency evaluated via theoretical methods was well accorded with reported experimental ones, following the same order as: -naphthyl- ligand > -naphthyl>p-anisdine>p-toluidine >o-toluidine >m-toluidine derivative. This research might provide a theoretical inhibition performance evaluation approach for homologous inhibitors.
Corrosion Inhibition of Carbon Steel In Sulfuric Acid by Sodium CaprylateIJERA Editor
The interaction of a sodium salt of octanoic acid, sodium caprylate (SC), with a carbon steel (CS) surface was
investigated, using range of experimental techniques. It was shown that SC acts as a good CS general corrosion
inhibitor, yielding a maximum corrosion inhibition efficiency of 77%. This high inhibition efficiency is
maintained even at higher temperatures. It was determined that SC inhibits both partial corrosion reactions, and
can thus be considered to be a mixed-type inhibitor. The adsorption of SC on the CS surface was described by
the Langmuir adsorption isotherm. It was found that this process is spontaneous, irreversible and driven by the
entropy gain. The CS surface morphology was studied by SEM and it was demonstrated that SC is a very
effective general corrosion inhibitor of CS. This also was confirmed by contact angle measurements which
showed that the CS surface became more hydrophobic when the SC was added to the solution.
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 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
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.
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
Inhibition, kinetic and thermodynamic effects of new Azo derivatives on iron ...Al Baha University
This investigation is designed to apply an advanced kinetic-thermodynamic model on the experimental data obtained from acidic and alkaline corrosion of iron using mono- and bis-azo dyes as corrosion inhibitors. The inhibition properties of the tested azo dyes on corrosion of iron in HNO3 and NaOH media were analyzed by gravimetric, thermometric and polarization measurements. The three studied methods gave consistent results. Polarization study showed that all the inhibitors are mixed type in acidic, act mainly as cathodic in alkaline solution. The synthesized azo dye derivatives exhibit good inhibition properties, obeys the Frumkin adsorption isotherm. The large values of the change in the standard free energy of adsorption (∆Goads), equilibrium constant (Kads) and binding constant (Kb) revealed that the reactions proceed spontaneously and result in highly efficient physisorption mechanism and stronger electrical interaction between the double layer existing at the phase boundary and the adsorbing molecules. The inhibition efficiency depends on the number of adsorption oxygen sites (OH and OMe groups), their charge density and π-electron clouds. The inhibition efficiency evaluated via theoretical methods was well accorded with reported experimental ones, following the same order as: -naphthyl- ligand > -naphthyl>p-anisdine>p-toluidine >o-toluidine >m-toluidine derivative. This research might provide a theoretical inhibition performance evaluation approach for homologous inhibitors.
Corrosion Inhibition of Carbon Steel In Sulfuric Acid by Sodium CaprylateIJERA Editor
The interaction of a sodium salt of octanoic acid, sodium caprylate (SC), with a carbon steel (CS) surface was
investigated, using range of experimental techniques. It was shown that SC acts as a good CS general corrosion
inhibitor, yielding a maximum corrosion inhibition efficiency of 77%. This high inhibition efficiency is
maintained even at higher temperatures. It was determined that SC inhibits both partial corrosion reactions, and
can thus be considered to be a mixed-type inhibitor. The adsorption of SC on the CS surface was described by
the Langmuir adsorption isotherm. It was found that this process is spontaneous, irreversible and driven by the
entropy gain. The CS surface morphology was studied by SEM and it was demonstrated that SC is a very
effective general corrosion inhibitor of CS. This also was confirmed by contact angle measurements which
showed that the CS surface became more hydrophobic when the SC was added to the solution.
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 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
Inhibitive properties, thermodynamic, kinetics and quantumAl Baha University
Inhibitive properties, thermodynamic, kinetics and quantum
chemical calculations of polydentate Schiff base compounds
as corrosion inhibitors for iron in acidic and alkaline media
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.
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
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.
Chemical and electrochemical studies of ranitidine as a corrosion inhibitor f...Premier Publishers
The corrosion inhibition of ranitidine on mild steel in hydrochloric acid medium was studied employing chemical and electrochemical methods. The results showed that the studied compound possessed good interaction on the metal surface and control both anodic and cathodic reactions. Studies pertaining to the determination of corrosion rate, percentage inhibition efficiency and variation of inhibitor concentration and temperature for the corrosion control process. Both anodic and cathodic polarized potentials were measured under galvanostatic and linear polarization techniques. The corrosion current density, corrosion potentials, Tafel slops and percentage inhibition efficiency were calculated. Thermodynamic parameters for the adsorption process were calculated and interpreted. The percentage inhibition efficiency obtained from both the methods was good agreement with each other. The corrosion protection was explained on the basis of adsorption of inhibitors on the metal surface. Adsorption of a compound on the mild steel surface was confirmed by FTIR spectra.
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.
Corrosion Inhibition of Carbon Steel In Sulfuric Acid by Sodium CaprylateIJERA Editor
The interaction of a sodium salt of octanoic acid, sodium caprylate (SC), with a carbon steel (CS) surface was
investigated, using range of experimental techniques. It was shown that SC acts as a good CS general corrosion
inhibitor, yielding a maximum corrosion inhibition efficiency of 77%. This high inhibition efficiency is
maintained even at higher temperatures. It was determined that SC inhibits both partial corrosion reactions, and
can thus be considered to be a mixed-type inhibitor. The adsorption of SC on the CS surface was described by
the Langmuir adsorption isotherm. It was found that this process is spontaneous, irreversible and driven by the
entropy gain. The CS surface morphology was studied by SEM and it was demonstrated that SC is a very
effective general corrosion inhibitor of CS. This also was confirmed by contact angle measurements which
showed that the CS surface became more hydrophobic when the SC was added to the solution.
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.
The inhibition effect of hydralazine hydrochloride on corrosion of mild steel...Premier Publishers
The inhibition effect of the Hydralazine hydrochloride for mild steel corrosion in 1M HCl has been investigated. Polarization measurement indicates that the Hydralazine hydrochloride act as mixed-type inhibitor, which gives a maximum inhibition efficiency around 72 %. Electrochemical impedance spectroscopy was used to investigate the mechanism of corrosion inhibition gives around 76 % due to the formation of electrical double layer. Thermodynamic parameter such as ΔG0 ads value was obtained as -30.22 KJ/mol indications that inhibitor shows its inhibition effect due to the chemisorptions process. Scanning electron microscopic images gives a visual idea about the formation of the protective film on the mild steel surface to reduce the corrosion rate. So that the Hydralazine hydrochloride acts as an efficient mixed type corrosion inhibitor for mild steel corrosion in acid media.
Inhibitive properties, thermodynamic, kinetics and quantum
chemical calculations of polydentate Schiff base compounds
as corrosion inhibitors for iron in acidic and alkaline media
Inhibitive properties, thermodynamic, kinetics and quantumAl Baha University
Inhibitive properties, thermodynamic, kinetics and quantum
chemical calculations of polydentate Schiff base compounds
as corrosion inhibitors for iron in acidic and alkaline media
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.
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
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.
Chemical and electrochemical studies of ranitidine as a corrosion inhibitor f...Premier Publishers
The corrosion inhibition of ranitidine on mild steel in hydrochloric acid medium was studied employing chemical and electrochemical methods. The results showed that the studied compound possessed good interaction on the metal surface and control both anodic and cathodic reactions. Studies pertaining to the determination of corrosion rate, percentage inhibition efficiency and variation of inhibitor concentration and temperature for the corrosion control process. Both anodic and cathodic polarized potentials were measured under galvanostatic and linear polarization techniques. The corrosion current density, corrosion potentials, Tafel slops and percentage inhibition efficiency were calculated. Thermodynamic parameters for the adsorption process were calculated and interpreted. The percentage inhibition efficiency obtained from both the methods was good agreement with each other. The corrosion protection was explained on the basis of adsorption of inhibitors on the metal surface. Adsorption of a compound on the mild steel surface was confirmed by FTIR spectra.
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.
Corrosion Inhibition of Carbon Steel In Sulfuric Acid by Sodium CaprylateIJERA Editor
The interaction of a sodium salt of octanoic acid, sodium caprylate (SC), with a carbon steel (CS) surface was
investigated, using range of experimental techniques. It was shown that SC acts as a good CS general corrosion
inhibitor, yielding a maximum corrosion inhibition efficiency of 77%. This high inhibition efficiency is
maintained even at higher temperatures. It was determined that SC inhibits both partial corrosion reactions, and
can thus be considered to be a mixed-type inhibitor. The adsorption of SC on the CS surface was described by
the Langmuir adsorption isotherm. It was found that this process is spontaneous, irreversible and driven by the
entropy gain. The CS surface morphology was studied by SEM and it was demonstrated that SC is a very
effective general corrosion inhibitor of CS. This also was confirmed by contact angle measurements which
showed that the CS surface became more hydrophobic when the SC was added to the solution.
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.
The inhibition effect of hydralazine hydrochloride on corrosion of mild steel...Premier Publishers
The inhibition effect of the Hydralazine hydrochloride for mild steel corrosion in 1M HCl has been investigated. Polarization measurement indicates that the Hydralazine hydrochloride act as mixed-type inhibitor, which gives a maximum inhibition efficiency around 72 %. Electrochemical impedance spectroscopy was used to investigate the mechanism of corrosion inhibition gives around 76 % due to the formation of electrical double layer. Thermodynamic parameter such as ΔG0 ads value was obtained as -30.22 KJ/mol indications that inhibitor shows its inhibition effect due to the chemisorptions process. Scanning electron microscopic images gives a visual idea about the formation of the protective film on the mild steel surface to reduce the corrosion rate. So that the Hydralazine hydrochloride acts as an efficient mixed type corrosion inhibitor for mild steel corrosion in acid media.
Inhibitive properties, thermodynamic, kinetics and quantum
chemical calculations of polydentate Schiff base compounds
as corrosion inhibitors for iron in acidic and alkaline media
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).
Experimental and Theoretical Investigation of Thiazolyl Blue as a Corrosion I...Al Baha University
The anticorrosion effect of thiazolyl blue (MTT) for copper in 3% NaCl at 298 K
was researched by electrochemical methods, scanning electron-microscopy (SEM), and atomic
force microscopy (AFM). The results reveal that MTT can protect copper efficiently, with a
maximum efficiency of 95.7%. The corrosion inhibition mechanism was investigated by X-ray
photoelectron spectroscopy (XPS), Fourier transform infrared spectral (FT-IR), and theoretical
calculation. The results suggest that the MTT molecules are adsorbed on metal surface forming a
hydrophobic protective film to prevent copper corrosion. It also indicates that the MTT and copper
form covalent bonds. The molecular dynamic simulation further gives the evidence for adsorption.
The adsorption isotherm studies demonstrate that a spontaneous, mixed physical and chemical
adsorption occurs, which obeys Langmuir adsorption isotherm. The present research can help us
better understand the corrosion inhibition process and improve it.
OXYSTELMA ESCULENTUM Stem Extracts as Corrosion Inhibitor for Mild Steel in A...IJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
International Journal of Modern Engineering Research (IJMER) covers all the fields of engineering and science: Electrical Engineering, Mechanical Engineering, Civil Engineering, Chemical Engineering, Computer Engineering, Agricultural Engineering, Aerospace Engineering, Thermodynamics, Structural Engineering, Control Engineering, Robotics, Mechatronics, Fluid Mechanics, Nanotechnology, Simulators, Web-based Learning, Remote Laboratories, Engineering Design Methods, Education Research, Students' Satisfaction and Motivation, Global Projects, and Assessment…. And many more.
Halogen-substituted pyrazolo-pyrimidine derivatives as corrosion inhibitors f...Al Baha University
Sulfuric acid is widely used in several industrial fields, such as acid pickling, acid cleaning and acid descaling, which cause serious corrosion issues. Especially, copper being widely applied in industrial is vulnerable to be corroded by the acid. The usage of corrosion inhibitor is one of the most important techniques for controlling the corrosion. Several organic inhibitors containing hetero-atom, π-electrons and double bond have been applied for the corrosion inhibition of copper, which are found to exhibit high inhibiting properties by providing electrons to interact with metal surface. However, the use of several heterocyclic inhibitors has caused negative impact on the environment due to their toxicity and non-biodegradability. In this paper, pyrazolo-pyrimidine derivatives are found to attract great attention owing to their eco-friendly properties. Corrosion inhibited properties of three pyrazolo-pyrimidine derivatives namely 4-amino pyrazolo-pyrimidine (APP), 3-bromine 4-amino pyrazolo-pyrimidine (Br-APP) and 3-iodine 4-amino pyrazolo-pyrimidine (I-APP) on copper in 0.5 M H2SO4 solution were studied using electrochemical method and surface analysis techniques. Corrosion of copper has been largely inhibited by the inhibitors and the inhibited efficiency increase with the augment of concentration. The adsorption isotherms were simulated to explore the adsorption mode of inhibitors. Furthermore, theoretical calculations were applied to research the mechanism of inhibitors on copper.
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
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Vaccine management system project report documentation..pdfKamal Acharya
The Division of Vaccine and Immunization is facing increasing difficulty monitoring vaccines and other commodities distribution once they have been distributed from the national stores. With the introduction of new vaccines, more challenges have been anticipated with this additions posing serious threat to the already over strained vaccine supply chain system in Kenya.
COLLEGE BUS MANAGEMENT SYSTEM PROJECT REPORT.pdfKamal Acharya
The College Bus Management system is completely developed by Visual Basic .NET Version. The application is connect with most secured database language MS SQL Server. The application is develop by using best combination of front-end and back-end languages. The application is totally design like flat user interface. This flat user interface is more attractive user interface in 2017. The application is gives more important to the system functionality. The application is to manage the student’s details, driver’s details, bus details, bus route details, bus fees details and more. The application has only one unit for admin. The admin can manage the entire application. The admin can login into the application by using username and password of the admin. The application is develop for big and small colleges. It is more user friendly for non-computer person. Even they can easily learn how to manage the application within hours. The application is more secure by the admin. The system will give an effective output for the VB.Net and SQL Server given as input to the system. The compiled java program given as input to the system, after scanning the program will generate different reports. The application generates the report for users. The admin can view and download the report of the data. The application deliver the excel format reports. Because, excel formatted reports is very easy to understand the income and expense of the college bus. This application is mainly develop for windows operating system users. In 2017, 73% of people enterprises are using windows operating system. So the application will easily install for all the windows operating system users. The application-developed size is very low. The application consumes very low space in disk. Therefore, the user can allocate very minimum local disk space for this application.
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
TECHNICAL TRAINING MANUAL GENERAL FAMILIARIZATION COURSEDuvanRamosGarzon1
AIRCRAFT GENERAL
The Single Aisle is the most advanced family aircraft in service today, with fly-by-wire flight controls.
The A318, A319, A320 and A321 are twin-engine subsonic medium range aircraft.
The family offers a choice of engines
2. 900
PROTECTION OF METALS AND PHYSICAL CHEMISTRY OF SURFACES Vol. 51 No. 5 2015
KARIMI et al.
the corrosion of mild steel in 1 M HCl, evaluated by
Tafel polarization and electrochemical impedance
spectroscopy (EIS) data. Effects of concentration and
temperature on the inhibition efficiencies of the
selected Schiff base have been studied systematically.
Thermodynamic parameters such as enthalpy, entropy
and Gibbs free energy were calculated from experi
mental data of the inhibition process at different tem
perature.
2. MATERIALS AND METHODS
2.1. Preparation of di (Resacetophenone) 1,2
cyclohexandiimine (R DACH)
All chemicals used in present work were of reagent
grade Merck product and used as received without fur
ther purification. The R DACH Schiff base (Fig. 1)
was prepared in high yeild (94%) by the condensation
of Resacetophenone (0.304 g, 2 mmol) with Cyclo
hexanediamine (0.114 g, 1 mmol) in a stirred ethan
olic solution and heated to reflux for 5 h according to
the described procedure [6]. The resulting dirty yellow
color precipitate was filtered off, washed with warm
ethanol and diethyl ether. Identification of structure of
synthesized Schiff base was performed by IR and
1
HNMR spectroscopy and elemental analysis.
2.2. Sample Preparation
Working electrodes were prepared from steel X52
specimens of the chemical composition: C 0.3, Mn
1.350, P 0.03, S 0.03 wt.%, and the balance Fe. Sam
ples were cut from a flat plate by the wire cut method.
The dimension of each sample is 1 cm × 1 cm. Working
electrodes were prepared by embedding the sample in
epoxy resin, exposing a geometrical surface area of 1
cm2
to the aggressive electrolyte. The exposed areas of
the electrodes were mechanically abraded with 400,
800, 1200 and 2000 grades of emery paper, rinsed by
distilled water and degreased with acetone before each
electrochemical experiment.
The measurements were performed in 1 M HCl in
the absence and presence of Schiff bases in the con
centration range from 5 × 10–5
to 2 × 10–3
M. Chemi
cals used in corrosion experiments were from Merck
grade and used without further purification. Distilled
water was used to prepare test solutions.
2.4. Electrochemical Measurements
Electrochemical measurements were carried out in
a conventional three electrode system. A reference
electrode was a saturated calomel electrode (SCE) and
the auxiliary electrode was a platinum sheet. All exper
iments were repeated three times. To reach the steady
state condition, before each experiment, the working
electrode was immersed in the test cell for 20 min. The
electrochemical measurements were carried out using
computer controlled ZAHNER potentiostat/gal
vanostat. Electrochemical impedance spectroscopy
(EIS) was recorded in frequency range of 100 kHz to
10 mHz with 0.01 V peak to peak amplitude using AC
signals at open circuit potential. Polarization curves
were scanned at a scan rate of 1 mV s–1
from –700 to
–100 mV. All tests were done at constant temperature
by controlling the cell temperature using a water bath.
Polarization curve was used to calculate corrosion cur
rent density by the Tafel extrapolation method. The
polarization resistance was calculated from the slope
of the potential versus logarithm of current plots. Fit
ting of experimental impedance spectroscopy data to
the proposed equivalent circuit was done by means of
home written least square software based on the Mar
quardt method for the optimization of functions and
Macdonald weighting for the real and imaginary parts
of the impedance [15, 16].
The morphology of steel surface after 12 h exposure
to 1 M HCl solution in the absence and presence of 2 ×
10–3
M R DACH was observed by scanning electron
microscope (SEM) model VEGA.
3. RESULTS AND DISCUSSION
3.1. Tafel Polarization Measurements
Figure 2 shows the anodic and cathodic polariza
tion plots of steel in 1 M HCl in the absence and pres
ence of different concentrations of inhibitor at 25°C.
Table 1 gives the electrochemical corrosion parame
ters such as corrosion potential (Ecorr vs. SCE), corro
sion current density (Jcorr), cathodic and anodic Tafel
slopes (βa, βb), the degree of surface coverage (θ) and
inhibition efficiency (IE) obtained by extrapolation of
the Tafel lines. The degree of surface coverage and
inhibition efficiency are calculated using the following
equations [17]:
(1)
(2)
where IE is the inhibition efficiency, Jcorr and are
the corrosion current densities determined by the
intersection of the extrapolated Tafel lines and the cor
rosion potential for mild steel in uninhibited and
θ
J·
corr Jcorr–
J·
corr
,=
IE% θ 100,×=
J·
corr
N N
OH
HOOH
HO
Fig. 1. The general structure of investigated Schiff bases.
3. PROTECTION OF METALS AND PHYSICAL CHEMISTRY OF SURFACES Vol. 51 No. 5 2015
ELECTROCHEMICAL INVESTIGATIONS ON THE INHIBITION BEHAVIOR 901
inhibited acid solution, respectively. Both the anodic
and cathodic reactions of mild steel corrosion inhib
ited in presence of the inhibitor. This result suggests
that the addition of the R DACH decreases the anodic
dissolution and also retards the hydrogen evolution
reaction. However, the influence was more pro
nounced in the anodic polarization plots compared to
that of the cathodic polarization plots. The corrosion
potential displayed small change and the curves
changed slightly towards the negative direction. These
results indicated that the presence of R DACH com
pound inhibited iron oxidation and the hydrogen and
oxygen evolution. Consequently these compounds can
be classified as the mixed corrosion inhibitors, as elec
trode potential displacement is lower than 85 mV in
any direction [18].
It can be seen that and inhibition efficiency (IE)
increased by increasing inhibitor concentration which
indicates that more inhibitor molecule are absorbed
on the metal surface thus providing wider surface cov
erage and these compound are acting as adsorption
inhibitor.
Polarization resistance (Rp) values were determined
using Stern Geary equation which is given below [19]:
(3)
By increasing the R DACH concentration, the
polarization resistance increases in the presence of
compound, indicating adsorption of the inhibitor on
the metal surface to block the active sites efficiently
and inhibit corrosion [20].
3.2. Electrochemical Impedance Spectroscopy
Figure 2 shows Nyquist plots recorded for the cor
rosion of steel in 1 M HCl solution without and with
different concentrations of inhibitor obtained at Ecorr.
The plots show a depressed capacitive loop which
arises from the time constant of the electrical double
layer and charge transfer resistance. The impedance of
the inhibited steel increases with increasing the R
DACH concentrations and consequently the inhibi
Rp
babc
2.303 ba bc+( )
1
Icorr
⎝ ⎠
⎛ ⎞ .=
tion efficiency increases. The equivalent circuit com
patible with the Nyquist diagram recorded in the pres
ence of inhibitor is depicted in Fig. 4. The simplest
approach requires the theoretical transfer function
Z(ω) to be represented by a parallel combination of a
resistance Rct and a capacitance Cdl, both in series with
another resistance Rs [21]:
(4)
where ο is the frequency in rad/s, ω = 2πf and f is fre
quency in Hz. To obtain a satisfactory impedance sim
ulation of steel, it is necessary to replace the capacitor
(C) with a constant phase element (CPE) Q in the
equivalent circuit [22]. The most widely accepted
explanation for the presence of CPE behavior and
Z ω( ) Rs
1
iωCdl
1
Rct
+
,+=
–1
–2
–3
–4
–5
–0.20
–0.25
–0.30–0.40
–0.45
–0.50–0.70
–0.35–0.55
–0.60
–6
–0.65
1
2 3
4
5
6
7
8
E/V
logJ(J/Acm–2
)
Fig. 2. Anodic and cathodic polarization curves of steel
electrode in 1 M HCl without and with various concentra
tion of inhibitor at 25°C: (1) Blank, (2) 5 × 10–5, (3) 1 ×
10–4
, (4) 2 × 10–4
, (5) 3 × 10–4
, (6) 5 × 10–4
, (7) 1 × 10–3
,
(8) 2 × 10–3
M.
Table 1. Potentiodynamic polarization parameters for the corrosion of steel in 1 M HCl solution in the absence and pres
ence of different concentrations of inhibitor at 25°C
Concentration, M βc, mV βa, mV Jcorr, μA cm–2 –E, mV Rp, Ω cm–2 θ IE
Blank 161 88 231.00 406.90 106.96 – –
5 × 10–5
150 83 115.00 400.00 201.75 0.50 50.22
1 × 10–4 158 86 84.00 373.00 287.87 0.64 63.64
2 × 10–4
155 85 62.00 371.00 384.75 0.73 73.16
3 × 10–4
153 84 51.30 381.00 458.29 0.78 77.79
5 × 10–4
149 68 38.00 370.40 533.53 0.84 83.55
1 × 10–3 153 67 33.60 357.50 600.91 0.85 85.45
2 × 10–3
126 61 24.60 364.40 723.08 0.89 89.35
4. 902
PROTECTION OF METALS AND PHYSICAL CHEMISTRY OF SURFACES Vol. 51 No. 5 2015
KARIMI et al.
depressed semicircles on solid electrodes is micro
scopic roughness, causing an inhomogeneous distri
bution in the solution resistance as well as in the dou
ble layer capacitance [22]. Constant phase element
Qdl, Rs and Rct can be corresponded to double layer
capacitance, Qdl = Rn – 1
solution resistance and
charge transfer resistance, respectively. To corroborate
the equivalent circuit, the experimental data are fitted
to equivalent circuit and the circuit elements are
obtained. Table 2 illustrates the equivalent circuit
parameters for the impedance spectra of corrosion of
steel in 1 M HCl solution. The results demonstrate
that the presence of inhibitor enhanced the value of Rct
obtained in the pure medium while the values of Qdl
decreased. The decrease in Qdl is caused by adsorption
of inhibitor, indicating that the exposed area
decreases. On the other hand, a decrease in Qdl, which
can result from a decrease in local dielectric constant
and/or an increase in the thickness of the electrical
Cdl
n
double layer, suggests that Schiff base inhibitor acts by
adsorption at the metal/solution interface [23].
The increase in values of Rct and the decrease in
values of Qdl with increasing the concentration also
indicate that Schiff base acts as primary interface
inhibitor and the charge transfer controls the corro
sion of steel under the open circuit conditions.
3.3. Effect of Temperature
The adsorption phenomenon has been successfully
explained by thermodynamic parameters [24, 25]. The
change of the corrosion rate with the temperature was
studied in in 1 M HCl. For this purpose, polarization
curves were performed at different temperatures from
25 to 65°C in the absence and presence of different
concentrations of R DACH (Figs. 5 and 6). For 45
and 65°C, the electrochemical parameters were
extracted and summarized in Tables 3 and 4. It is obvi
ous that the values of Jcorr increases by increasing the
temperature in both solutions and the efficiency value
decreases. Figures 5 and 6 show that raising the tem
perature has no significant effect on the corrosion
potentials but leads to a higher corrosion rate. Accord
ing to the Arrhenius equation, the apparent activation
energy (Ea) of metal corrosion in both media (Blank
250
200
150
000
50
8007006004003001000 500200
Zim/ohm
Zre/ohm
1
2
3
4
5 6
7
8
Fig. 3. Nyquist plots for steel in 1 M HCl without and with
various concentration of inhibitor at 25°C: (1) Blank,
(2) 5 × 10–5
, (3) 1 × 10–4
,(4) 2 × 10–4
, (5) 3 × 10–4
, (6) 5 ×
10–4, (7) 1 × 10–3, (8) 2 × 10–3 M.
Rs
Qdl
Rct
Fig. 4. Equivalent circuits compatible with the experimen
tal impedance data for corrosion of steel electrode in dif
ferent inhibitors concentrations.
Table 2. Impedance spectroscopy data for steel corrosion in 1 M HCl solution with and without different concentration of
inhibitor at 25°C
Concentration Rs, Ω Rct, Ω Qdl, F n
Blank 2.9 86 0.005 0.74
5 × 10–5
3.1 131 3.00E 03 0.81
1 × 10–4
2.8 430 1.00E 03 0.7
2 × 10–4
9.1 582 8.00E 04 0.65
3 × 10–4
13.3 618 8.00E 04 0.65
5 × 10–4
13.6 621 5.00E 04 0.71
1 × 10–3
14.5 679 7.00E 04 0.67
2 × 10–3
14.7 751 8.00E 04 0.68
5. PROTECTION OF METALS AND PHYSICAL CHEMISTRY OF SURFACES Vol. 51 No. 5 2015
ELECTROCHEMICAL INVESTIGATIONS ON THE INHIBITION BEHAVIOR 903
and inhibited) can be calculated from the following
equation [26]:
(5)
where Ea represents the apparent activation energy, R
is the gas constant, A is the pre exponential factor, and
T is the absolute temperature. Figure 7 shows the log
arithm of Jcorr against the reciprocal of temperature T–1
in the absence and presence of R DACH. The activa
tion energy Ea is calculated from the slope of the plots
(–Ea R–1
). The calculated value of Ea in the absence of
inhibitor is 58.5 kJ mol–1
, while in the presence of 2 ×
10–3
M of inhibitor, it is 72.4 kJ mol–1
. It has been
reported that higher Ea in presence of inhibitor for
mild steel in comparison with blank solution typically
shows physisorption [27]. Enthalpy and entropy of
Jcorrln A
Ea
RT
,–ln=
activation (ΔHa, ΔSa) are calculated from the transi
tion state theory [27]:
(6)
where h is the Plank constant and N is the Avogadro’s
number. A plot of ln(Jcorr T–1
) versus T–1
gave straight
lines as shown in Fig. 9 for mild steel dissolution in 1
M HCl in the absence and presence of different concen
trations of R DACH. Straight lines are obtained with a
slope of –ΔHa R–1 and an intercept of ln(RN–1h–1) +
ΔSaR–1
. The values of Ea, A, ΔHa and ΔSa are calcu
lated and given in Table 5. The positive values of ΔHa
mean that the dissolution reaction is an endothermic
process. Practically, Ea and ΔHa are of the same order.
Also, the entropy ΔSa increases more positively with
Jcorr
RT
Nh⎝ ⎠
⎛ ⎞ ΔSa
R⎝ ⎠
⎛ ⎞ ΔHa–
RT⎝ ⎠
⎛ ⎞ ,expexp=
0
–1
–3
–4
–5
–0.2–0.3–0.4–0.5–0.5–0.7
E/V
logJ(J/Acm–2
)
–6
–2 1
2
3
Fig. 5. Anodic and cathodic polarization curves of steel
electrode in 1M HCl without inhibitor at different temper
atures: (1) 25, (2) 45, (3) 65°C.
Table 3. Potentiodynamic polarization parameters for the corrosion of steel in 1 M HCl solution in the absence and pres
ence of different concentrations of inhibitor at 45°C
Concentration βc, mV βa, mV Jcorr, μA cm–2
–E, mV Rp, Ω cm–2
θ IE
Blank 181 108 969 408 30.31 – –
5 × 10–5
171 104 543 410 51.71 0.44 43.96
1 × 10–4 167 102 380 399 72.36 0.61 60.78
2 × 10–4 134 84.6 295 402.9 76.33 0.70 69.56
3 × 10–4
122 77.9 233 395.2 88.60 0.76 75.95
5 × 10–4 130 76.8 227 388.5 92.35 0.77 76.57
1 × 10–3
116 76 192 392.5 103.84 0.80 80.19
2 × 10–3
110 71 158 395.3 118.58 0.84 83.69
–1
–3
–4
–5
–0.2–0.3–0.4–0.5–0.5–0.7
E/V
logJ(J/Acm–2)
–6
–2
1
2
3
Fig. 6. Anodic and cathodic polarization curves of steel
electrode in presence of 2 × 10–3
M of inhibitor at different
temperatures: (1) 25, (2) 45, (3) 65°C.
6. 904
PROTECTION OF METALS AND PHYSICAL CHEMISTRY OF SURFACES Vol. 51 No. 5 2015
KARIMI et al.
the presence of the inhibitor. This reflects that the acti
vated complex in the rate determining step represents
dissociation rather than an association step, meaning
that an increase in disordering takes place on going
from reactants to the activated complex [6].
3.4. Adsorption Isotherm
Adsorption isotherms provide information about
the interaction of the adsorbed molecules with the
metal surface. The adsorption of organic compounds
Table 4. Potentiodynamic polarization parameters for the corrosion of steel in 1 M HCl solution in the absence and pres
ence of different concentrations of inhibitor at 65°C
Concentra
tion
βc, mV βa, mV
Jcorr,
μA cm–2 –E, mV Rp, Ω cm–2
θ IE
Blank 188 118 3990 403 7.89 – –
5 × 10–5
174 115 2423 419 12.41 0.39 39.27
1 × 10–4
163 98 1654 421.7 16.07 0.59 58.55
2 × 10–4
156 87 1110 407.5 21.85 0.72 72.18
3 × 10–4
151 85.4 1060 408.6 22.35 0.73 73.43
5 × 10–4
143 85 913 396 25.35 0.77 77.12
1 × 10–3
122 88 832 397 26.68 0.79 79.15
2 × 10–3
134 78 786 388 27.24 0.80 80.30
9
8
7
6
5
4
0.00340.00330.00320.00310.00300.0029
logJ(J/Acm–2)
3
1
2
3
4
5
6
7
8
T–1/K–1
Fig. 7. Typical Arrhenius plots of lnJcorr vs. T–1
for steel in
1 M HCl at different concentration of inhibitor : () Blank,
(᭜) 5 × 10–5
, (᭡) 1 × 10–4
, (×) 2 × 10–4
, (*) 3 × 10–4
, (–) 5 ×
10–4
, (᭹) 1 × 10–3
, (+) 2 × 10–3
M.
3
2
1
0
–1
–2
0.00340.00330.00320.00310.00300.0029
1
2
3
4
5
6
7
8
–3
lnJcorrT–1(JT–1/Acm–2K–1)
T–1
/K–1
Fig. 8. Variation of lnJcorr T–1
vs. T–1
for steel in 1 M HCl
at different concentration of inhibitor: () Blank, (᭜) 5 ×
10–5
, (᭡) 1 × 10–4
, (×) 2 × 10–4
, (*) 3 × 10–4
, (–) 5 × 10–4
,
(᭹) 1 × 10–3
, (+) 2 × 10–3
M.
Table 5. Activation parameters of dissolution of steel in 1 M HCl solution in the absence and presence of inhibitor
Concentration, M
Ea,
kJ mol–1
A,
A cm–2
ΔHa,
kJ mol–1
ΔSa,
J mol–1
K–1
Ea –ΔHa,
kJ mol–1
Blank 58.50 4.22E + 12 55.86 –8.63 2.64
5 × 10–5 63.75 1.68269E + 13 61.11 –0.40 2.63
1 × 10–4 62.33 6.90316E + 12 59.69 –7.81 2.63
2 × 10–4 60.42 2.43995E + 12 57.78 –1.64 2.64
3 × 10–4
63.32 6.24624E + 12 60.68 –8.64 2.63
5 × 10–4
66.64 1.88399E + 13 64.01 0.53 2.63
1 × 10–3
67.22 2.06348E + 13 64.59 1.30 2.64
2 × 10–3 72.54 1.28635E + 14 69.91 16.51 2.63
7. PROTECTION OF METALS AND PHYSICAL CHEMISTRY OF SURFACES Vol. 51 No. 5 2015
ELECTROCHEMICAL INVESTIGATIONS ON THE INHIBITION BEHAVIOR 905
can be expressed by two main types of interactions:
physical adsorption and chemical adsorption. There
are some factors that influence the adsorption pro
cesses including the nature and charge of metal, the
chemical of inhibitor, and the type of electrolyte [28].
The adsorption of an organic adsorbate at
metal/solution interface can be presented as a substi
tution adsorption process between the organic mole
cules in aqueous solution, Org(sol), and the water mol
ecules on metallic surface, H2O(ads):
(7)
where Org(sol) and Org(ads) are the organic species dis
solved in the aqueous solution and adsorbed onto the
metallic surface, respectively, H2O(ads) is the water
molecule adsorbed on the metallic surface, H2O(sol) is
water molecule in solution, and x is size ratio and rep
resents the number of molecules of water replaced by
inhibitor molecule.
Different adsorption isotherms, Langmuir,
Temkin, Freundlich, Frumkin, Modified, Langmuir,
Henry, Viral, Damaskin, Volmer, and Flory Huggins,
[29, 30] were tested for their fit to the experimental
data. The linear regression coefficient values (R2
) were
determined from the plotted curves. According to
these results it was found that the experimental data
obtained from polarization readings could be fitted by
Langmuir’s adsorption isotherm. According to this
isotherm, the surface coverage is related to inhibitor
concentration by [30, 31]:
(8)
(9)
where Kads is the equilibrium constant of the inhibitor
adsorption process, C is the inhibitor concentration
and θ is the surface coverage that was calculated by Eq.
(1).
A fitted straight line is obtained for the plot of C θ–1
versus C with slopes close to 1 as seen in Fig. 9. The
strong correlation (R2
> 0.99) suggests that the adsorp
tion of R DACH on the mild steel surface obeys Lang
muir’s adsorption isotherm. This isotherm assumes
that the adsorbed molecules occupy only one site and
there are no interactions with other adsorbed species
[30]. The Kads values can be calculated from the inter
cept lines on the C θ–1 axis. This is related to the stan
dard free energy of adsorption (ΔGads) with the follow
ing equation [32]:
(10)
where R is the gas constant and T is the absolute tem
perature. The constant value of 55.5 is the concentra
tion of water in solution in Molar. The enthalpy and
entropy of adsorption (ΔHads and ΔSads) can be calcu
lated using the following equations [23]:
(11)
Org sol( ) xH2O ads( )+ Org ads( ) xH2O sol( ),+
θ
1 θ–
KadsC,=
C
θ
1
Kads
C+ ,=
ΔGads RT 55.5Kads( ),ln–=
ΔGads ΔHads TΔSads,–=
(12)
The negative values of ΔGads suggest that the
adsorption of R DACH on the steel surface is sponta
neous. Generally, the values of –ΔGads around or less
than 20 kJ mol–1 are associated with the electrostatic
interaction between charged molecules and the
charged metal surface (physisorption); while those
around or higher than 40 kJ mol–1
mean charge shar
ing or transfer from the inhibitor molecules to the
metal surface to form a coordinate type of metal bond
(chemisorption). The values of Kads and ΔGads are listed
in Table 6. The ΔGads values are around –36 kJ mol–1
,
which means that the absorption of inhibitor on the
steel surface belongs to both physisorption and chemi
sorption, and the adsorptive film has an electrostatic
character [20]. Figure 10 represents the plots of lnKads
versus T–1 for adsorption R DACH. The obtained
lines can provide valuable information about the
mechanism of corrosion inhibition. An endothermic
adsorption process ΔHads > 0 is attributed unequivo
cally to chemisorption, and an exothermic adsorption
Kadsln
ΔHads
RT
ΔSads
R
55.5( )ln .–+–=
3.0
2.5
2.0
1.5
1.0
0.5
0.00200.00150.00100.00050
1
2
3
103Cθ–1/moll–1
C/mol l–1
Fig. 9. Langmuir adsorption isotherm Cθ–1
vs. C of inhib
itor in 1 M HCl at different temperatures: ( 25°C,
᭜ 45°C, ᭡ 65°C).
Table 6. Thermodynamic and equilibrium adsorption param
eters for adsorption of inhibitor on steel surface in 1 M HCl
solution
T, K Kads, M–1
ΔGads, KJ mol–1
298 –34.37 19083.97
318 –36.55 18214.94
338 –38.71 17361.11
8. 906
PROTECTION OF METALS AND PHYSICAL CHEMISTRY OF SURFACES Vol. 51 No. 5 2015
KARIMI et al.
process ΔHads < 0 may involve either physisorption or
chemisorption or a mixture of both processes [33].
The calculated values of ΔHads and ΔSads are –1.97 kJ
and 108.71 J mol–1 K–1, respectively. The calculated
ΔGads and ΔHads values for inhibitor show that the
adsorption mechanism is not completely physical or
chemical, and a combination of physisorption and
chemisorption exists between the inhibitor and metal
surface. The positive sign of ΔSads arises from the sub
stitution process, which can be attributed to the
increase in the solvent entropy and more positive water
desorption entropy. It is also interpreted with an
increase of disorders due to the more water molecules
which can be desorbed from the metal surface by one
inhibitor molecule [21]
3.6. Chronoamperometry
In order to gain more insight about the effect of R
DACH on the electrochemical behavior of steel in 1 M
HCl solution, potentiostatic current time transients
were recorded. Figure 11 shows the current transients
of steel electrode at –0.3 V (vs. SCE) applied anodic
potential. Initially the current decreases monotoni
cally with time, and the decrease in the current density
is due to the formation of corrosion products layer on
the anode surface. However, in later time, the current
reaches to a steady state value due to the steel dissolu
tion depending on applied potential (Fig. 11). In pres
ence of inhibitor, the dissolution current decreased
and electrode inhibited from corrosion due to inhibi
tor adsorption.
3.7. Scanning Electron Microscopy
In order to evaluate the conditions of the steel sur
faces in contact with hydrochloric acid solution, sur
face analysis was carried out. Surface was observed
before and after 12 h of immersion in 1 M HCl in the
absence and presence of R DACH at 25°C. Scanning
6.82
6.80
6.78
6.76
6.74
6.72
6.70
0.00340.00330.00320.00310.00300.0029
6.68
lnKabs/1mol–1
T–1/K–1
Fig. 10. lnKads vs. T–1
for inhibitor adsorption on steel sur
face.
0.014
0.018
0.012
0.010
0.008
0.006
0.004
0.002
10008006004002000
0.016
1
2
I/mA
t/s
Fig. 11. Current transients of steel electrode at –0.3 V vs.
SCE: (1) Blank, (2) 2 × 10–3
M of inhibitor.
(b)
(а) 20 µm
20 µm
Fig. 12. Scanning electron microscopyimages of steel
exposed to 1 M HCl solution (a) in the absence of inhibitor
(b) in the presence of 2 × 10–3
M of inhibitors.
9. PROTECTION OF METALS AND PHYSICAL CHEMISTRY OF SURFACES Vol. 51 No. 5 2015
ELECTROCHEMICAL INVESTIGATIONS ON THE INHIBITION BEHAVIOR 907
electron microscopy (SEM) studies of the surface in
the absence and presence of inhibitor are presented in
Fig. 12. The SEM reveals the presence of corrosion
attack and some pits on the surface in the absence of
inhibitor while such damages are diminished in the
presence of inhibitor.
4. CONCLUSION
1. The synthetic Schiff base R DACH acts as an
inhibitor for mild steel corrosion in 1 M HCl solution,
especially in high concentration.
2. Inhibition efficiency of this compound increases
with increasing their concentrations due to the forma
tion of a film on the steel. The inhibitor decreased both
anodic and cathodic Tafel current, which showed the
mixed mode of action of the inhibitor molecules.
3. The inhibition of mild steel in 1 M HCl solution
at different temperatures was found to obey the Lang
muir adsorption isotherm.
4. The negative values of ΔG indicate the spontane
ous adsorption of the inhibitor on the surface of mild
steel.
5. Surface studies show that the surface of sample
in solution with inhibitor molecules looks more flat
and more uniform with lower roughness than that in
the uninhibited solution.
REFERENCES
1. Kayadibi, F., Sagdinc, S.G., and Kara, Y.S., Prot. Met.
Phys. Chem. Surf., 2015, vol. 51, p. 143.
2. Sobhi, M., Prot. Met. Phys. Chem. Surf., 2014, vol. 50,
p. 825.
3. Zor, S., Prot. Met. Phys. Chem. Surf., 2014, vol. 50,
p. 530.
4. Ghasemi, O., Danaee, I., Rashed, G.R., et al., J. Cent.
South Univ. Technol. (Engl. Ed.), 2013, vol. 20, p. 301.
5. Shalabi, K., Fouda, A.S., Elewady, G.Y., and El
Askalany, A., Prot. Met. Phys. Chem. Surf., 2014,
vol. 50, p. 420.
6. Jafari, H., Danaee, I., Eskandari, H., and Rashvan
davei, M., Ind. Eng. Chem. Res., 2013, vol. 52, p. 6617.
7. Sagdinc, S.G. and Kara, Y.S., Prot. Met. Phys. Chem.
Surf., 2014, vol. 50, p. 111.
8. Avdeev, Y.G., Luchkin, A.Y., and Kuznetsov, Y.I., Prot.
Met. Phys. Chem. Surf., 2013, vol. 49, p. 865.
9. Shpan’ko, S. P., Grigor’ev, V.P., Anisimova, V.A., et al.,
Prot. Met. Phys. Chem. Surf., 2013, vol. 49, p. 859.
10. Gholami, M., Danaee, I., Maddahy, M.H., and Rash
vandavei, M., Ind. Eng. Chem. Res., 2013, vol. 52,
p. 14875.
11. Abdallah, M., Asghar, B.H., Zaafarany, I., and Sobhi,
M., Prot. Met. Phys. Chem. Surf., 2013, vol. 49, p. 485.
12. Baghaei Ravari, F. and Dadgareenezhad, A., Prot. Met.
Phys. Chem. Surf., 2015, vol. 51, p. 138.
13. Danaee, I., Ghasemi, O., Rashed, G.R., et al., J. Mol.
Struct., 2013, vol. 1035, p. 247.
14. Fouda, A.S., Abdallah, M., and Medhat, M., Prot. Met.
Phys. Chem. Surf., 2012, vol. 48, p. 477.
15. Macdonald, J.R., Solid State Ionics, 1984, vol. 13,
p. 147.
16. Danaee, I., J. Electroanal. Chem., 2011, vol. 662,
p. 415.
17. Negm, N.A., Elkholy, Y.M., Zahran, M.K., and Taw
fik, S.M., Corros. Sci., 2010, vol. 52, p. 3523.
18. Hegazy, M.A., Corros. Sci., 2009, vol. 51, p. 2610.
19. Keles, H., Mater. Chem. Phys., 2011, vol. 130, p. 1317.
20. Emregul, K.C. and Atakol, O., Mater. Chem. Phys.,
2003, vol. 82, p. 188.
21. Hoseinzadeh, A.R., Danaee, I., and Maddahy, Y.M.H.,
Z. Phys. Chem., 2013, vol. 227, p. 403.
22. Danaee, I., Niknejad Khomami, M., and Attar, A.A.,
Mater. Chem. Phys., 2012, vol. 135, p. 658.
23. Hoseinzadeh, A.R., Danaee, I., and Maddahy, M.H.,
J. Mater. Sci. Technol., 2013, vol. 29, p. 884.
24. Badr, G.E., Corros. Sci., 2009, vol. 51, p. 2529.
25. Hegazy, M.A., Ahmed, H.M., and El Tabei, A.S., Cor
ros. Sci., 2011, vol. 53, p. 671.
26. Aljourani, J., Raeissi, K., and Golozar, M.A., Corros.
Sci., 2009, vol. 51, p. 1836.
27. Herrag, L., Chetouani, A., Elkadiri, S., et al., Port.
Ectrochim. Acta, 2008, vol. 26, p. 211.
28. Oguzie, E.E., Unaegbu, C., Ogukwe, C.N., et al.,
Mater. Chem. Phys., 2004, vol. 84, p. 363.
29. Mu, G., Li, X., Qu, Q., and Zhou, J., Corros. Sci.,
2006, vol. 48, p. 445.
30. Bayol, E., Gurtenb, T., Gurtena, A.A., and Erbil, M.,
Mater. Chem. Phys., 2008, vol. 112, p. 624.
31. Keles, H., Keles, M., Dehri, I., and Serindag, O.,
Mater. Chem. Phys., 2008, vol. 112, p. 173.
32. Dogru Mert, B., Erman Mert, M., Kardas, G., and
Yazici, B., Corros. Sci., 2011, vol. 53, p. 4265.
33. Li, X.H., Deng, S.D., Fu, H., and Mu, G.N., Corros.
Sci., 2009, vol. 51, p. 2639.