Analysis of Transport Properties and Acoustical Parameters of Sulphanilamide ...IOSR Journals
Sulphanilamide is the parent compound of all the sulpha-durgs which is important in urinary tract infections and meningococcal meningitis profilaxes. Ultrasonic velocity measurements are highly sensitive to molecular interactions and used to provide qualitative informations about the physical nature and strength of the molecular ∕inter-ionic interactions. In the present work, non-aqueous solutions of Sulphanilamide have been prepared with different concentrations and the experiments were carried out from a low temperature of 50c to a high temperature of 550c. The ultrasonic velocity data combined with density and viscosity provides the standard means for determining the internal pressure, free volume and acoustical parameters. The various interactions occurring in the solutions are interpreted interms of ion-ion and ion-solvent interactions. An attempt is made to identify the entry of solvate into the samples and the entry of drug molecules into the solvate which supports to identify the molecular structure.
Using Ethylthiazole-4-Carboxylate as Inhibitor for Copper Corrosion in 0.5 M ...paperpublications3
Abstract: In this research was the study effect of ethylthiazole-4-carboxylate as inhibitor on copper corrosion in 0.5M HCl acid by using weight loss and polarization methods, results showed of decrease corrosion current density and corrosion rate with increasing inhibitor concentration of corrosion at 30 C and corresponding increase the efficiency of inhibition and surface coverage, the same way for the temperature of 40 and 50 C , where efficiency decreases depending on the temperature increase. Increase the inhibitor concentration, increased energy both activation, enthalpy and free of adsorption and decreased entropy energy, and this shows that the inhibitor has good energy to activate the process of adsorption and desorption be chemical type from good type inhibitor. Formation layer of film due found oxygen, nitrogen and sulphur molecules which have a crucial role to build the film.
Analysis of Transport Properties and Acoustical Parameters of Sulphanilamide ...IOSR Journals
Sulphanilamide is the parent compound of all the sulpha-durgs which is important in urinary tract infections and meningococcal meningitis profilaxes. Ultrasonic velocity measurements are highly sensitive to molecular interactions and used to provide qualitative informations about the physical nature and strength of the molecular ∕inter-ionic interactions. In the present work, non-aqueous solutions of Sulphanilamide have been prepared with different concentrations and the experiments were carried out from a low temperature of 50c to a high temperature of 550c. The ultrasonic velocity data combined with density and viscosity provides the standard means for determining the internal pressure, free volume and acoustical parameters. The various interactions occurring in the solutions are interpreted interms of ion-ion and ion-solvent interactions. An attempt is made to identify the entry of solvate into the samples and the entry of drug molecules into the solvate which supports to identify the molecular structure.
Using Ethylthiazole-4-Carboxylate as Inhibitor for Copper Corrosion in 0.5 M ...paperpublications3
Abstract: In this research was the study effect of ethylthiazole-4-carboxylate as inhibitor on copper corrosion in 0.5M HCl acid by using weight loss and polarization methods, results showed of decrease corrosion current density and corrosion rate with increasing inhibitor concentration of corrosion at 30 C and corresponding increase the efficiency of inhibition and surface coverage, the same way for the temperature of 40 and 50 C , where efficiency decreases depending on the temperature increase. Increase the inhibitor concentration, increased energy both activation, enthalpy and free of adsorption and decreased entropy energy, and this shows that the inhibitor has good energy to activate the process of adsorption and desorption be chemical type from good type inhibitor. Formation layer of film due found oxygen, nitrogen and sulphur molecules which have a crucial role to build the film.
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.
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
Oxidative Coupling: A Tranquil Approach for Determination of Selexipag by Vis...Ratnakaram Venkata Nadh
The present study is a first report on development of a spectrophotometric method for determination of selexipag (used to cure pulmonary arterial hypertension) in bulk and tablet formulation and its validation. The basis of the proposed method is formation of a chromophore (of λ max 600 nm) in presence of acidic ferric chloride by oxidative coupling reaction between selexipag and MBTH (3-methylbenzo-thiazolin-2-one hydrazone) solution. Regression analysis (r > 0.999) shows that the plotted calibration curve exhibits good linearity in the studied range of concentration (5 – 30 μg mL-1). As per the existing guidelines of ICH, various parameters of the method were tested for validation. Low values of R.S.D. (< 2%) were observed indicating that the proposed method is reproducible, accurate and precise
Inhibitory Effect of Some Carbazides on Corrosion of Aluminium in Hydrochloric Acid and Sodium Hydroxide Solutions
The dissolution of aluminium in hydrochloric acid and sodium hydroxide solutions in the presence of semicarbazide, thiosemicar- bazide and sym.dipheny1carbazide as corrosion inhibitors has been studied using thermometric, weight-loss and polarization methods. The three methods gave consistent results. The higher inhibition efficiency of these compounds in acidic than in alkaline madia may be due to the less negative potential of aluminium in hydrochloric acid solution, favouring adsorption of the additive.The adsorption of these compounds were found to obey Frurnkin adsorption isotherm. Cathodic polarization measurements showed that these com- pounds are cathodic inhibitors and their adsorption in the double layer does not change the mechanism of the hydrogen evolution reaction. The results are analysed in terms of both molecular and cationic adsorption.
Partial Molar Volumes of Tetra alkyl ammonium salts in 10%(W/W) 2-(Ethoxy) et...Premier Publishers
In this article densities and apparent molar volumes of Tetra alkyl ammonium bromide salts ( ) in 10% (W/W) 2-(Ethoxy) ethanol-water mixture is studied at 30o, 35o and 40oC. Partial molar volumes are divided into ionic components using different methods such as Conway et al. and Jolicoeur et al. The results are compared with the values of partial molar volumes of ions reported in literature for pure water. Decrease in hydrophobic hydration is noticed. This may be due to the addition of co-solvent 2-(Ethoxy) ethanol (confirming the conclusions drawn from our viscosity studies that in 2-(Ethoxy) ethanol-water mixture, the structuredness of water is reduced by the breaking of hydrogen bonds). The values are divided into and . Making use of the Padova’s equation values of salts are calculated. These are also divided into ionic contributions. Dimensions of ions have been calculated to understand solvation behavior. It is shown that the classification of salts into structure makers and structure breakers on the basis of the sign of is not valid for the present water rich mixed solvent system.
Thermal properties and size distribution of lignins precipitated with sulphur...Michal Jablonsky
Dissolution and fractionation of lignocellulosic material is a critical step of valorisation of lignins. Precipitated lignin was isolated from black liquor by sulphuric acid at four levels of concentration (5, 25, 50 and 72 % wt). A comparison study was performed through thermal and size properties. Theacid concentration influences of thermal properties of precipitated lignin. The acid concentration has an effect on changes in particle size of precipitated lignin. The results of thermogravimetric analysis indicated that the highest degradation of lignins appeared as an exothermic peak in range 470 - 650°C.The greatest weight loss in this section under an oxidation atmosphere was in the following order lignin 25 % wt (47.3 %), followed by lignin 72 % wt (45.0 %), lignin 5 % wt (43.6 %), and, smallest decline reached by lignin 50 % wt. The lowest temperature at the maximum degradation rate was determined for a sample of lignin 72 % wt at 488°C.
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.
Kinetics of Substituted Bis- and Mono-azo Dyes as Corrosion Inhibitors for Al...Al Baha University
This investigation is designed to apply an advanced kinetic^thermodynamic model on the data obtained from acidic and alkaline corrosion of aluminium using bis- and mono-azo dyes as corrosion inhibitors.
Spectral studies of 5-({4-amino-2-[(Z)-(2-hydroxybenzylidene) amino] pyrimidi...IOSR Journals
Some transition metal ions Complexes with 5-({4-amino-2-[(Z)-(2-hydroxybenzylidene) amino]
pyrimidin-5-yl} methyl)-2,3,4-trimethoxybenzene were prepared and characterized by elemental analyses,
Infrared , magnetic moment, electronic spectra , mass spectra, X-ray powder diffraction, molar conductance
and thermal analysis (TGA). The complexes have general formulae [ML2.2H2O] {where M = Mn (II), Co (II), Ni
(II), Cu (II), Zn (II), Pd (II) and Pt (II). The coordination behavior of the metal ions towards to the investigated
Schiff base takes place through –C=N,-NH2 and –OH groups. The obtained C, H and N elemental analysis data
showed the Metal: Ligand ratio is 1:2 [M: L] ratio. The molar conductance data reveal that all the metal
complexes are non-electrolytic in nature. From the magnetic moments the complexes are paramagnetic except
Zn metal ion complexes have octahedral geometry with coordination number eight. The thermal behavior of
these complexes shows that, the hydrated complexes have loses two water molecules and immediately followed
by decomposition of the anions and ligand molecules in the second and third stage. The Schiff bases and metal
complexes show good activity against some bacteria. The antimicrobial results indicate that, the metal
complexes have better antimicrobial activity as compared to the prepared Schiff base.
Determination of temperature regions in thermal degradation of ligninMichal Jablonsky
In this paper, industrial lignins were characterized by elemental analysis (EA) and thermogravimetry (TG). The aim was to find the main intervals of lignin degradation and maximum rate of their degradation. The results obtained can be helpful in finding the applicability of the materials at their thermal decomposition. The differences between individual lignins have been confirmed by EA and TG.
Synthesis and characterization of some metal complexes of 2- Phenyl-3,4-dihyd...IOSRJAC
2-Phenyl-3,4-dihydro-quinazolin-4-yloxy)-acetic acid (L1) metal complexes with Mn2+ , Co2+, Ni2+ Cu2+ , and Zn2+ ions were studied and the structure of the complexes were elucidated using elemental analyses, infrared (IR), 1H nuclear magnetic resonance (NMR), magnetic moment and thermal analysis measurements. Besides the characterization of complexes by physicochemical technique, Biological activities of the synthesized complexes were examined against some microbial strains for evaluation of antibacterial and antifungal activities.
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.
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
Oxidative Coupling: A Tranquil Approach for Determination of Selexipag by Vis...Ratnakaram Venkata Nadh
The present study is a first report on development of a spectrophotometric method for determination of selexipag (used to cure pulmonary arterial hypertension) in bulk and tablet formulation and its validation. The basis of the proposed method is formation of a chromophore (of λ max 600 nm) in presence of acidic ferric chloride by oxidative coupling reaction between selexipag and MBTH (3-methylbenzo-thiazolin-2-one hydrazone) solution. Regression analysis (r > 0.999) shows that the plotted calibration curve exhibits good linearity in the studied range of concentration (5 – 30 μg mL-1). As per the existing guidelines of ICH, various parameters of the method were tested for validation. Low values of R.S.D. (< 2%) were observed indicating that the proposed method is reproducible, accurate and precise
Inhibitory Effect of Some Carbazides on Corrosion of Aluminium in Hydrochloric Acid and Sodium Hydroxide Solutions
The dissolution of aluminium in hydrochloric acid and sodium hydroxide solutions in the presence of semicarbazide, thiosemicar- bazide and sym.dipheny1carbazide as corrosion inhibitors has been studied using thermometric, weight-loss and polarization methods. The three methods gave consistent results. The higher inhibition efficiency of these compounds in acidic than in alkaline madia may be due to the less negative potential of aluminium in hydrochloric acid solution, favouring adsorption of the additive.The adsorption of these compounds were found to obey Frurnkin adsorption isotherm. Cathodic polarization measurements showed that these com- pounds are cathodic inhibitors and their adsorption in the double layer does not change the mechanism of the hydrogen evolution reaction. The results are analysed in terms of both molecular and cationic adsorption.
Partial Molar Volumes of Tetra alkyl ammonium salts in 10%(W/W) 2-(Ethoxy) et...Premier Publishers
In this article densities and apparent molar volumes of Tetra alkyl ammonium bromide salts ( ) in 10% (W/W) 2-(Ethoxy) ethanol-water mixture is studied at 30o, 35o and 40oC. Partial molar volumes are divided into ionic components using different methods such as Conway et al. and Jolicoeur et al. The results are compared with the values of partial molar volumes of ions reported in literature for pure water. Decrease in hydrophobic hydration is noticed. This may be due to the addition of co-solvent 2-(Ethoxy) ethanol (confirming the conclusions drawn from our viscosity studies that in 2-(Ethoxy) ethanol-water mixture, the structuredness of water is reduced by the breaking of hydrogen bonds). The values are divided into and . Making use of the Padova’s equation values of salts are calculated. These are also divided into ionic contributions. Dimensions of ions have been calculated to understand solvation behavior. It is shown that the classification of salts into structure makers and structure breakers on the basis of the sign of is not valid for the present water rich mixed solvent system.
Thermal properties and size distribution of lignins precipitated with sulphur...Michal Jablonsky
Dissolution and fractionation of lignocellulosic material is a critical step of valorisation of lignins. Precipitated lignin was isolated from black liquor by sulphuric acid at four levels of concentration (5, 25, 50 and 72 % wt). A comparison study was performed through thermal and size properties. Theacid concentration influences of thermal properties of precipitated lignin. The acid concentration has an effect on changes in particle size of precipitated lignin. The results of thermogravimetric analysis indicated that the highest degradation of lignins appeared as an exothermic peak in range 470 - 650°C.The greatest weight loss in this section under an oxidation atmosphere was in the following order lignin 25 % wt (47.3 %), followed by lignin 72 % wt (45.0 %), lignin 5 % wt (43.6 %), and, smallest decline reached by lignin 50 % wt. The lowest temperature at the maximum degradation rate was determined for a sample of lignin 72 % wt at 488°C.
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.
Kinetics of Substituted Bis- and Mono-azo Dyes as Corrosion Inhibitors for Al...Al Baha University
This investigation is designed to apply an advanced kinetic^thermodynamic model on the data obtained from acidic and alkaline corrosion of aluminium using bis- and mono-azo dyes as corrosion inhibitors.
Spectral studies of 5-({4-amino-2-[(Z)-(2-hydroxybenzylidene) amino] pyrimidi...IOSR Journals
Some transition metal ions Complexes with 5-({4-amino-2-[(Z)-(2-hydroxybenzylidene) amino]
pyrimidin-5-yl} methyl)-2,3,4-trimethoxybenzene were prepared and characterized by elemental analyses,
Infrared , magnetic moment, electronic spectra , mass spectra, X-ray powder diffraction, molar conductance
and thermal analysis (TGA). The complexes have general formulae [ML2.2H2O] {where M = Mn (II), Co (II), Ni
(II), Cu (II), Zn (II), Pd (II) and Pt (II). The coordination behavior of the metal ions towards to the investigated
Schiff base takes place through –C=N,-NH2 and –OH groups. The obtained C, H and N elemental analysis data
showed the Metal: Ligand ratio is 1:2 [M: L] ratio. The molar conductance data reveal that all the metal
complexes are non-electrolytic in nature. From the magnetic moments the complexes are paramagnetic except
Zn metal ion complexes have octahedral geometry with coordination number eight. The thermal behavior of
these complexes shows that, the hydrated complexes have loses two water molecules and immediately followed
by decomposition of the anions and ligand molecules in the second and third stage. The Schiff bases and metal
complexes show good activity against some bacteria. The antimicrobial results indicate that, the metal
complexes have better antimicrobial activity as compared to the prepared Schiff base.
Determination of temperature regions in thermal degradation of ligninMichal Jablonsky
In this paper, industrial lignins were characterized by elemental analysis (EA) and thermogravimetry (TG). The aim was to find the main intervals of lignin degradation and maximum rate of their degradation. The results obtained can be helpful in finding the applicability of the materials at their thermal decomposition. The differences between individual lignins have been confirmed by EA and TG.
Synthesis and characterization of some metal complexes of 2- Phenyl-3,4-dihyd...IOSRJAC
2-Phenyl-3,4-dihydro-quinazolin-4-yloxy)-acetic acid (L1) metal complexes with Mn2+ , Co2+, Ni2+ Cu2+ , and Zn2+ ions were studied and the structure of the complexes were elucidated using elemental analyses, infrared (IR), 1H nuclear magnetic resonance (NMR), magnetic moment and thermal analysis measurements. Besides the characterization of complexes by physicochemical technique, Biological activities of the synthesized complexes were examined against some microbial strains for evaluation of antibacterial and antifungal activities.
ماذا أنت يا إلهي ؟ ماذا أنت إلا الرب الإله ! لأنه من هو السيد إلا الرب ؟ ومن هو الإله سوي إلهنا ؟ 0
عـــال جداً ! صـــالح جداً ! قـــوي جداً ! مقـــتدر جداً !
رؤوف جداً ومع ذلك عادل جداً ! 000 مستتر للغاية ومع ذلك ظاهر جداً !000 جميل جداً ومع ذلك قاس جداً ! 000 دائم ومع ذلك لا يمكن إدراكه ! 000 ثابت ومع ذلك يغير كل شئ ! 000 أباً حديث وعتيق علي الإطلاق ! 000 يجدد الكل ويعطي المتكبرين أياماً وهم لا يعلمون ! 000 دائم يعمل ومستريح إلي الغاية ! 000 دائماً يحشد ومع ذلك غير محتاج إلي شئ ! 000 يدعم ويسد العوز ويستر ! 000 يبدع ويعول وينمي ! 000 يطلب ومع ذلك يملك كل شئ ! 0
* * *
أنت تحب بلا شهوة وغيور بلا قلق ! 000 تندم ومع ذلك لا تأسف ! 000 أنت حانق ومع ذلك أنت هادئ ! 000 تغير كل أعمالك وغرضك ثابت ! 000 تأخذ كل ما تجده ومع ذلك أنت لا تضيعه أبداً ! 000 لا تحتاج مطلقاً إلي شئ ومع ذلك تسر بالأرباح ! 000 لست طماعاً ومع ذلك تطالب بالأرباح ! 000 تأخذ كثيراً لكي تصير مديوناً ومن عنده شئ وليس هو ملكك ؟ 000 أنت تدفع ديوناً ليس لهل أصل وتعيد ديونا دون أن تنقص منها شيئاً ! 000 ماذا أقول عنك الآن يا إلهي يا حياتي وقرحي الطاهر !؟ 000 وماذا يقول أي إنسان عندما يتكلم عنك ! ؟ 000 ويل لمن لا يتحدث بحمدك عندما ينطق الأخرس ويصير كأفصح البلغاء ! 0
Inhibition Effect of Hydantoin Compounds on the Corrosion of Iron in Nitric a...Al Baha University
The inhibition of corrosion of iron in 2M nitric acid and 2M sulfuric acid solutions by substituted phenylhydantoin, thiohydantoin, and dithiohydantoin compounds was measured using thermometric, weight loss, and polarization methods. The three methods gave consistent results. The polarization curves indicated that the hydantoin compounds act as mixed-type inhibitors. The adsorption of the inhibitors were found to obey the Temkin adsorption isotherm. The higher inhibition ef®ciency of the additives in nitric with respect to sulfuric acid solution may be attributed to the reduced formation of soluble quaternary nitrogen salts in nitric acid medium, favouring adsorption of the parent additive on the metal surface. The obtained results indicate that the corrosion rate of iron in both acids increases with increasing temperature, both in absence and presence of the tested inhibitors. Kinetic-thermodynamic model functions and Temkin isotherm data are compared and discussed. The synergistic effect of halide anions on the inhibition ef®ciency of the hydantoin compounds was also investigated.
Inhibition of Copper Corrosion by Arylazotriazoles in Nitric Acid Solution Al Baha University
. A study has been made to investigate the effect of some azoheterocyclic dyes of the type 3-arylazo 1,2,4-triazole (AT) on the corrosion of copper exposed to 0.5M nitric acid solution at different temperatures and at different AT concentrations. Using potentiodynamic polarization and Tafel electrochemical methods, it can be shown that AT compounds are good inhibitors of copper corrosion in HNO 3 solution. The kinetic and thermodynamic parameters of the inhibited system were determined. The high inhibition efficiency of these compounds may be due to the adsorption of the additive itself and/or the adsorption of the formed Cu(II)-AT complexes at the polarized electrode interface. Cathodic polarization measurements showed that AT dyes are predominantly cationic inhibitor
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.
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.
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.
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.
Properties of Zinc Phosphate Coatings on Carbon Steel Using a Thermostatic Ce...CrimsonPublishersACSR
Properties of Zinc Phosphate Coatings on Carbon Steel Using a Thermostatic Cell and a Mobile System by Reyes Astivia MJE, Torres JV*, Barrera GM and Díaz CB in Annals of Chemical Science Research
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.
Simple and Effective Method of the Synthesis of Nanosized Fe2O 3particlesIOSR Journals
Abstract: Nanosized Iron oxide is prepared by using precipitation method from iron nitrate and liquid ammonia. Thermal analysis shows that synthesized iron oxide shows some weight loss and oxide undergoing decomposition, dehydration or any physical change from TGA curve we observe that Iron oxide shows stable weight loss above 4000C. In DTA curve also, there is exothermic and endothermic peak. Which shows phase transition, solid state reaction or any chemical reaction occurred during heating treatment. Morphology is observed by scanning electron microscopy (SEM) shows particles are nanosized. Further morphology observation by Transmission Electron Microscopy (TEM) revels that Iron Oxide has the corundum (Al2O3) structure. Magnetic measurements shows that iron oxide has five unpaired electron and strongly paramagnetic character.
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
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.
2001 complete
1. Monatshefte fuÈr Chemie 132, 245±258 (2001)
Inhibition Effect of Hydantoin Compounds
on the Corrosion of Iron in Nitric
and Sulfuric Acid Solutions
Loutfy H. Madkour, Amera M. Hassanein, Mohamed M. GhoneimÃ,
and Safwat A. Eid
Chemistry Department, Faculty of Science, Tanta University, 31527 Tanta, Egypt
Summary. The inhibition of corrosion of iron in 2 M nitric acid and 2 M sulfuric acid solutions by
substituted phenylhydantoin, thiohydantoin, and dithiohydantoin compounds was measured using
thermometric, weight loss, and polarization methods. The three methods gave consistent results. The
polarization curves indicated that the hydantoin compounds act as mixed-type inhibitors. The
adsorption of the inhibitors were found to obey the Temkin adsorption isotherm. The higher inhibition
ef®ciency of the additives in nitric with respect to sulfuric acid solution may be attributed to the
reduced formation of soluble quaternary nitrogen salts in nitric acid medium, favouring adsorption of
the parent additive on the metal surface. The obtained results indicate that the corrosion rate of iron in
both acids increases with increasing temperature, both in absence and presence of the tested
inhibitors. Kinetic-thermodynamic model functions and Temkin isotherm data are compared and
discussed. The synergistic effect of halide anions on the inhibition ef®ciency of the hydantoin
compounds was also investigated.
Keywords. Acid corrosion; Inhibition; Iron; Hydantoins; Synergistic effect.
Introduction
One of today's most important considerations in industry is the reduction of overall
costs by protection and maintenance of materials used. Because iron is the back-
bone of industrial constructions, the inhibition of iron corrosion in acidic solutions
has been studied in considerable detail. Many N-heterocyclic compounds with polar
groups and/or %-electrons are ef®cient inhibitors for iron corrosion in acidic media
[1]. These organic molecules can adsorb on the metal surface, forming a bond
between the electron pair of the nitrogen and/or the %-electron cloud and the metal,
thereby reducing the corrosive attack [1, 2]. It has also been reported that the
inhibition ef®ciency of sulfur-containing compounds is superior to that of nitrogen-
containing ones [3]. In nearly all cases there was evidence of chemisorption of the
inhibitor, and the inhibitors were of a mixed type, i.e. both the anodic and cathodic
polarization processes were affected. No research work is available in the literature
à Corresponding author
2. to date about the application of hydantoin compounds as inhibitors for surface metal
corrosion. Accordingly, the objective of this work is to study the hydantoin com-
pounds effects toward corrosion process of iron in nitric and sulfuric acid solutions
and also to determine the adsorption isotherms and to compare them with kinetic-
thermodynamic models of corrosion inhibition.
Results and Discussion
Thermometric measurements
The temperature change of the system involving iron in 2 M HNO3 or 2 M H2SO4
was followed in the absence as well as in the presence of different concentrations of
compound 3 as an example (Fig. 1). Upon increasing the concentration of the
additive, the time required to reach Tmax increases. This indicates that the inhibitor
retards the dissolution of iron in both corrosive acidic media, presumably by
Fig. 1. Temperature vs. time curves of iron corrosion in 2 M HNO3 in the absence and in the
presence of different concentrations of 3
246 L. H. Madkour et al.
3. adsorption onto the surface of the metal. The extent of retardation depends on the
degree of coverage of the metal surface with the adsorbate. The temperature vs. time
curves provide a means of differentiating between weak and strong adsorption [4].
Strong adsorption is noted in both acidic solutions, since a simultaneous increase in
t and a diminution in Tmax takes place, and both factors cause a large decrease in RN
(reduction in reaction number) of the system. The results reported in Table 1 reveal
that the inhibition ef®ciency of the additive, as determined from the percentage
reduction in RN, increases with increasing concentration of additives. Figure 2
shows the relation between % RN and the molar concentration of different additives.
The curves obtained are invariably sigmoid in nature, substantiating the idea that the
present inhibitors retard the corrosion rate by adsorption according to the Temkin
isotherm [5] (Eq. (1)).
ˆ c1 Á ln…c2 Á c† …1†
Fig. 2. Effect of additives concentration on % reduction in reaction number (% RN) of iron corrosion
in 2 M HNO3
Hydantoin Derivatives as Corrosion Inhibitors 247
4. In Eq. (1), c is the concentration of the additive in the bulk of the solution, is the
degree of coverage of the investigated metal surface by the adsorbed molecules,
and c1 and c2 are constants. The order of increasing the inhibition ef®ciency of the
hydantion compounds as determined by % RN is 3 2 4 1 6 5 7.
Weight loss measurements
Figure 3 shows the effect of the time of immersion on the corrosion of iron in 2 M
H2SO4 solution in the absence as well as in the presence of different amounts of 3.
The curves obtained in the presence of additives fall below that of the free acid. The
Table 1. Effect of concentration 3 on the thermometric parameters of Fe in 2 M HNO3
c/mol Á ia
C maxa
C t/min Át/min log RNa
CÁ % Red Á
dmÀ3
…Átamin† minÀ1
in RN
0 35.0 59.0 60 0.400
5 Â 10À7
35.0 45.9 75 15 1.18 0.686 0.150 62.5
1 Â 10À6
35.0 44.0 75 15 1.18 0.749 0.120 70.0
5 Â 10À6
34.8 44.0 90 30 1.48 0.791 0.100 75.0
1 Â 10À5
35.1 42.2 90 30 1.48 0.835 0.078 80.5
5 Â 10À5
34.9 39.8 105 45 1.65 0.899 0.048 88.0
1 Â 10À4
35.0 40.1 120 60 1.78 0.921 0.041 89.8
Fig. 3. Weight loss vs. time curves of iron corrosion in 2 M H2SO4 in the absence and in the presence
of different concentrations of 3 at 303 K
248 L. H. Madkour et al.
5. weight loss of iron depends on type and concentration of the additive in a similar
way as thermometric measurements do. The ef®ciency of the inhibitors under
investigation increases in the order 3 2 4 1 6 5 7. The inhibition effect may
be explained by considering the adsorption of the hydantoin molecules (with high
negative charge density at the hetero atom) on the metal surface [6, 7] consisting of
iron atoms with incomplete d shells [8]. Also, formation of a metal-inhibitor com-
plex on the corroding iron surface (surface chelation) may play a role [9].
Polarization measurements
Anodic and cathodic polarization of iron was carried out under potentiostatic
conditions in 2 M HNO3 and 2 M H2SO4 in the absence as well as in the presence of
different concentrations of inhibitor at 303 K. Figure 4 shows the polarization curves
of iron in 2 M nitric acid solution at different concentrations of 3; the results
obtained for the other compounds were quite similar. The inhibition ef®ciency
depends on many factors including number of adsorption sites or functional groups,
basicity, and molecular size. In the present case, the N-atom and the O-atom
probably act as the centers of adsorption, their basicity being affected by the
character of the substituents in -position. The results show that the inhibitive
power increases with increasing chain length: 3-carbethoxy-1-phenylhydantoin (3)
is found to be the most ef®cient inhibitor. This may be attributed to the presence of
the carbethoxy group which increases the electron density on the molecule and
provides an active adsorption center (oxygen atom) in addition to the two nitrogen
centers already present.
Fig. 4. Potentiostatic polarization curves of iron in 2 M HNO3 in the absence and in the presence of
different concentrations of 3
Hydantoin Derivatives as Corrosion Inhibitors 249
6. On the other hand, 1,3-dimethyl-5-phenylazo-2-thiohydantoin (6) has the lowest
inhibition ef®ciency owing to the formation of an iron complex (see formula)
which is obviously less adsorbed in acidic solutions. This interpretation is
supported experimentally by spectroscopic analysis (mainly ultraviolet spectra).
The Temkin adsorption isotherm is found to be ideally obeyed in acidic solutions
(Fig. 5), indicating that the main inhibition process takes place through adsorption
[10, 11].
The degree of surface coverage () by the adsorped molecules was calculated
from Eq. (2), where u0 and u are the dissolution rates of iron in the absence and in
the presence of hydantoins, respectively.
ˆ …1 À uau0† …2†
From Table 2 it can be seen that the three different techniques afford the same
results for the inhibition of corrosion of iron in both acidic media.
Fig. 5. Variation of iron surface coverage () with the logarithmic concentration of different additives
in 2 M HNO3 at 303 K
250 L. H. Madkour et al.
7. Effect of temperature
The effect of temperature on the rate of corrosion of iron in 2 M HNO3 and 2 M
H2SO4 containing 1 Â 10À5
M hydantoin was studied in the temperature range of
303±323 K. The corrosion rate increases with increasing temperature in the absence
as well as in the presence of the inhibitors. The increase of icorr is due to the absence
of a protective layer at the iron surface. Thus, the increase of temperature enhances
both the iron dissolution and the additive desorption processes without leading to
Fe(II)-hydantoin complex formation. The protective layer decreases as the
temperature increases.
The Arrhenius parameters as purely empirical quantities enable us to discuss the
variation of rate constants with temperature. It was found experimentally that a plot
of lnk against 1aT gives a straight line according to Eq. (3) [5].
lnk ˆ lnA À EaaRT …3†
The activation energies calculated from the slopes of lnIcorr vs. 1aT plots (Fig. 6)
are reported in Table 3.
The enthalpy change of activation (ÁHz
) can be calculated from Eq. (4), the
free energy change of activation (ÁGz
) is obtained from the Eyring equation [12]:
(Eq. (5)). Another convenient form of Eq. (5) is Eq. (6).
ÁHz
ˆ Ea À RT …4†
k ˆ
kBT
h
eÀÁGz
aRT
…5†
ÁGz
ˆ RT Á
lnkBT
h
À lnk
…6†
From ÁHz
and ÁGz
, the entropy change of activation (ÁSz
) can be obtained
according to Eq. (7).
ÁSz
ˆ …ÁHz
À ÁGz
†aT …7†
Table 2. Comparison between the inhibition ef®ciency of 1±7 in 2 M acid solutions as determined by
thermometric, weight loss, and polarization methods (1 Â 10À4
M inhibitor, 303 K)
% Inhibition
Inhibitor Thermometric Weight loss Polarization
HNO3 H2SO4 HNO3 H2SO4 HNO3 H2SO4
1 71.4 74.4 78 73 75.7 88.2
2 85.5 80.9 87 82 90.9 90
3 92.1 88.3 90 85 93.8 91
4 77.3 77.1 85 76 84.8 90
5 62.5 60.1 74 66 69.6 87.3
6 64.9 64.9 76 63 74.1 88.1
7 53.8 53.1 69 59 68.3 81.4
Hydantoin Derivatives as Corrosion Inhibitors 251
8. Fig. 6. Arrhenius plot of the current corrosion rate constant (icorr) vs. 1aT of iron in (a) 2 M HNO3
and (b) 2 M H2SO4 in the absence and in the presence of 1 Â 10À5
M hydantoin inhibitors
252 L. H. Madkour et al.
9. From the thermodynamic parameters in Table 3 it can be seen that Ea increases as
the inhibition ef®ciency of the additives increases. This suggests that the process is
controlled by a surface reaction, since the energy of activation for the corrosion
process is above 20 kJ Á molÀ1
[13]. The Ea value for iron dissolution in 5 M H2SO4
has been reported as 20X2 kJ Á molÀ1
[12] and 51.4 kJ molÀ1
[14±16]. For iron in 3 M
HCl and 1 M HNO3, an Ea values of 11.8 kJ Á molÀ1
has been reported [17], whereas
in 2 M HNO3 20.06 kJ Á molÀ1
have been found [18].
Generally, one can say that the nature and the concentration of the electrolyte
greatly affect the activation energy of the corrosion process. The presence of the
inhibitor causes a change in the value of the apparent activation energy. Thus, it
indicates no change in the rate-determining step brought about by the presence of
the hydantoin inhibitor.
Kinetic-thermodynamic model of corrosion inhibition
To evaluate the kinetic parameters and correlate them to the corrosion inhibition
mechanism, it is of value to analyze the kinetic data obtained in the presence of
hydantoin inhibitors from the standpoint of the generalized mechanistic scheme
proposed by El-Awady et al. [19, 20]. Table 4 comprises the values of 1ay which
give the number of active sites occupied by a single organic molecule; K is the
binding constant [21]. The values of B (equilibrium constant) and f (lateral
interaction parameter, 1/c1) are also reported in Table 4. The large negative values
of ÁG
indicate that the reaction proceeds spontaneously and is accompanied by a
high ef®cient adsorption. Large values of K and B (c2) point to better inhibition
ef®ciency of the tested hydantoin compounds, i.e. stronger electrical interaction
between the double layer at the phase boundary and the adsorbing molecules. In
general, the equilibrium constant of the adsorption process was found to rise with
increasing inhibition ef®ciency.
Table 3. Activation energy (Ea), enthalpy change (ÁHz
), free energy change (ÁGz
), and entropy change (ÁSz
) for the
dissolution of Fe in 2 M acid in the presence of 1 Â 10À5
M inhibitor at 313 K
Inhibitor
Ea
kJ Á molÀ1
ÁHz
kJ Á molÀ1
ÁGz
kJ Á molÀ1
ÀÁSz
J Á KÀ1
Á molÀ1
HNO3 H2SO4 HNO3 H2SO4 HNO3 H2SO4 HNO3 H2SO4
No 8.98 7.27 6.38 4.67 71.54 71.68 208.18 214.09
1 40.15 23.84 37.55 21.24 75.55 72.82 121.40 164.79
2 38.97 30.15 36.37 27.55 76.35 73.38 127.73 146.42
3 38.40 32.07 35.80 29.47 76.65 73.63 130.51 141.09
4 43.29 27.56 40.69 24.96 75.81 73.14 112.20 153.93
5 30.71 20.90 28.11 18.30 74.77 72.50 149.07 173.16
6 29.47 22.35 26.87 19.75 75.26 72.56 154.60 168.72
7 23.92 20.31 21.32 17.71 74.45 72.36 169.74 174.60
Hydantoin Derivatives as Corrosion Inhibitors 253
10. Synergistic effects of halide anions
The effects of IÀ
, BrÀ
, and ClÀ
on the polarization curves of iron at 298 K in the
absence and presence of hydantoin inhibitors in 0X5 M H2SO4 solution were studied.
The in¯uence on the inhibition ef®ciency was observed in presence of each anion
alone or in the presence of any of the different additives together with the anion.
The extent of the effect follows the order IÀ
BrÀ
ClÀ
. Since the iodide ions have
a higher inductive effect than BrÀ
and ClÀ
[22], they are less attached to the metal
surface and, consequently, easily displaced by the inhibitor molecules. The net
increment of the inhibition ef®ciency is de®ned in Eq. (8), where Px and Pinh are the
protection ef®ciency of the anion and inhibitor, respectively, and Ptot is the total
protection ef®ciency of the corrosive medium containing the anion and inhibitor
together.
ÁP ˆ Ptot À …Px ‡ Pinh† …8†
The correlation of ÁP vs. logc for the applied synergistic anions in acidic solution
was studied. Since the halide anions interact strongly with the iron surface due to
chemisorption [23, 24], the inhibitory effect is strengthened due to the coadsorption
of the anions. As a result, the surface coverage area …ÁP† and, consequently, the
inhibition ef®ciency both increase. KI is the most effective among the investigated
salts. Addition of 10À3
M KI in the presence of a very low concentration
…1 Â 10À5
M† of 3 rises the inhibition ef®ciency from 48 to 93% as shown in
Table 5.
Table 4. Curve ®tting of data to the kinetic-thermodynamic model (r ˆ 0X94) and the Temkin isotherm for hydantoin
inhibitors in 2 M acid at 303 K
Kinetic model Temkin isotherm
Medium 1ay K
ÀÁG
kJ Á molÀ1
1
C1
C2 Â 104 ÀÁG
kJ Á molÀ1
1 HNO3 12.50 1X30 Â 109
41.96 7X20 Â 10À4
133.10 24.46
H2SO4 6.67 5X47 Â 108
39.82 1X51 Â 10À3
16.72 19.44
2 HNO3 10.77 1X63 Â 1010
53.93 1X32 Â 10À2
254.61 26.03
H2SO4 5.88 9X63 Â 1010
52.62 2X56 Â 10À3
141.25 24.60
3 HNO3 8.43 1X01 Â 1012
58.44 6X43 Â 10À2
258.67 26.09
H2SO4 8.24 5X02 Â 1011
56.71 3X35 Â 10À2
243.60 25.93
4 HNO3 9.10 1X90 Â 109
42.90 1X12 Â 10À3
167.49 25.02
H2SO4 7.14 5X57 Â 109
45.57 1X85 Â 10À3
32.69 21.06
5 HNO3 4.79 9X50 Â 108
41.19 2X16 Â 10À4
87.70 23.45
H2SO4 10.75 1X15 Â 108
35.96 6X56 Â 10À4
2.72 15.04
6 HNO3 8.33 1X20 Â 109
41.77 4X90 Â 10À4
118.85 24.19
H2SO4 5.88 3X59 Â 108
38.78 1X26 Â 10À3
13.55 18.93
7 HNO3 3.96 2X30 Â 108
37.64 9X36 Â 10À5
68.07 22.84
H2SO4 5.56 1X69 Â 107
31.21 1X76 Â 10À4
2.30 14.63
254 L. H. Madkour et al.
11. Experimental
Iron specimens and electrolytes
Iron specimens (0.16% C, 0.05% Si, 0.37% Mn, 0.015% S) were used in the present study. Prior to
each experiment, the electrodes were mechanically polished with successive grades of emery paper,
degreased in pure acetone, washed in running bidistilled water, dried, and weighed before being
inserted in the cell to remove any oxide layer or corrosion product from the surface [25, 26]. 2 M
nitric and 2 M sulfuric solutions were prepared by diluting Analar reagents by bidistilled water.
Additives
The structural formulae of the investigated hydantoin derivatives 1±7 are given below.
The compounds were prepared according to methods reported in the literature [27±29]. Their
purity was checked by melting point determinations and spectroscopy. The hydantoin solutions were
prepared by dissolving the appropriate amount of compound in 25 cm3
Analar EtOH. The desired
volume of the free inhibitor was added to the electrolyte solution. The solvent effect must be
considered by mixing a de®nite volume of EtOH to the free acid to reach a constant ratio of EtOH in
each test in the absence and presence of different concentrations of inhibitor.
Thermometric measurements
The reaction vessel used was basically the same as that described by Mylius [30]. An iron piece
…1 Â 10 Â 0X1 cm† was immersed in 30 cm3
of either 2 M HNO3 or 2 M H2SO4 in the absence and
presence of additives, and the temperature of the system was followed as a function of time. The
procedure for the determination of the metal dissolution rate by the thermometric method has been
described previously [4, 30]. The reaction number (RN) is de®ned as given in Eq. (9) [31].
RN ˆ …Tmax À Ti†at …9†
Tmax and Ti are the maximum and initial temperatures, respectively, and t is the time (in minutes)
required to reach the maximum temperature. The percent reduction in RN [32] is then given as
……RNfree À RNinh†aRNfree† Â 100.
Table 5. Electrochemical parameters of Fe in the presence of 10À3
M KI and different concentrations of 3 in 0X5 M H2SO4
at 298 K
logC
mol Á dmÀ3
Ecorr
mV vsX SCE
icorr
mAacm2
Rcorr
mpy
c
V Á decadeÀ1
c
V Á decadeÀ1
% lnh
Free acid À506 10.72 4.92 0.123 0.049 ±
1 Â 10À3
M KI À471 9.57 4.39 0.113 0.042 10.7
1 Â 10À5
M 3 À482 5.60 2.57 0.113 0.046 47.8
1 Â 10À3
M KI ‡ 1 Â 10À3
M 3 À438 0.77 0.35 0.111 0.041 92.8
1 Â 10À4
M 3 À438 0.77 0.35 0.111 0.041 92.8
1 Â 10À3
M KI ‡ 1 Â 10À4
M 3 À431 0.75 0.34 0.115 0.032 93.0
1 Â 10À3
M 3 À445 0.73 0.34 0.107 0.025 93.2
1 Â 10À3
M KI ‡ 1 Â 10À3
M 3 À420 0.72 0.33 0.109 0.035 93.3
1 Â 10À2
M 3 À395 0.63 0.28 0.108 0.026 94.2
1 Â 10À3
M KI ‡ 1 Â 10À2
M 3 À440 0.41 0.19 0.102 0.022 96.2
Hydantoin Derivatives as Corrosion Inhibitors 255
12. Weight loss measurements
The reaction basin used in this method was a graduated glass vessel of 6 cm inner diameter and a total
volume of 250 cm3
. 100 cm3
of the test solution at 303X0 Æ 1X0 K were employed in each experiment.
The iron pieces (2 Â 2 Â 0X1 cm) were prepared as described before, weighed, and suspended under
the surface of the test solution by about 1 cm by suitable glass hooks. After speci®ed periods of time,
three pieces of iron were taken out of the test solution, rinsed with doubly distilled water, dried, and
re-weighed. The average weight loss at a certain time for each test of three samples was taken. The
percentage of inhibition (% In) of different concentrations of the inhibitors was calculated according
to 7 In ˆ WtX loss …pure†ÀWtX loss …inh†
WtX loss …pure† Â 100.
256 L. H. Madkour et al.
13. Polarization measurements
A conventional three-electrode cell was used with a 1.0 cm2
Pt sheet as the counter electrode which
was separated from the main cell compartment by a glass sinter. The potentials of the working
electrode were referred to a saturated calomel electrode (SCE). In order to avoid contamination, the
reference electrode was connected to the working electrode through a salt bridge ®lled with test
solution. The tip of the bridge was pressed against the working electrode in order to compensate the
ohmic drop. Prior to each experimental measurement, the solution under investigation (25 cm3
) was
freed of oxygen by passing prewashed pure nitrogen through it for a suf®cient time. Measurements
were performed on a planar disk electrode (A ˆ 1 cm2
). The iron electrodes were carefully degreased,
and the edges were masked by appropriate resins (Duracryle, Spofa-Dental, Praha). The surface of the
iron electrodes were prepared by mechanical grinding and polishing as given elsewhere [25, 26]. The
electrodes were rinsed in an ultrasonic bath containing bidistilled water and ®nally washed with
bidistilled water immediately before being immersed in the cell. The pretreatment procedure was
repeated before each experiment.
Anodic and cathodic potentiostatic polarization curves of iron electrodes were measured with a
Wenking Potentioscan Model POS 73. Potentials and currents were determined by digital
multimeters. Corrosion current densities (icorr) were determined by extrapolation of the anodic and
cathodic Tafel lines to the free corrosion potential value (Ecorr). Each experiment was conducted with
a freshly prepared solution and with newly polished electrodes. The cell temperature was kept
constant at 303X0 Æ 1X0 K in an ultra-thermostat.
References
[1] Trabanelli G (1987) In: Mansfeld F (ed) Chemical Industries: Corrosion Mechanism, chap 3.
Dekker, New York
[2] Schmitt G (1984) Br Corros J 19: 165
[3] Makhlouf M, El-Shatory SA, El-Said A (1996) J Mat Chem Phys 43: 76
[4] Aziz K, Shams El-Din AM (1965) Corros Sci 5: 489
[5] Atkins PW (1998) Physical Chemistry 6th edn. Oxford University Press, Oxford
[6] Hung G, Jian L (1982) Sci Sin B (Engl Edn) 25: 565
[7] Eldakar N, Nobe K (1981) Corrosion-NACE 36: 5
[8] Rozenfeld IL (1983) Corrosion Inhibition. McGraw-Hill, New York
[9] Subramanyam NC, Mayanna SM (1985) Corros Sci 25: 169
[10] Sieverts A, Leuez Z (1923) Z Anorg Chem 126: 524
[11] Gileadi E (1966) J Electroanal Chem 2: 137
[12] Parthetier S, Souchary K (1967) Chemical Kinetics. Elsevier, New York, p 155
[13] Fouda AS, El-Asklany AH, Madkour LH (1984) Indian J Chem Soc 61: 425
[14] Hudson RM, Butter TJ, Warning CJ (1977) Corros Sci 17: 571
[15] Selim M, Yassin A, Attya B (1977) Corros Sci 17: 923
[16] Attya BG, Abo El-Khair BM, Al-Qasimi R (1982) Corros Sci 22: 217
[17] Gomha S (1991) PhD Thesis, Univ of Mansoura, Egypt
[18] El-Gaber AS, Madkour LH, El-Asklany AH, Fouda AS (1997) Bulletin of Electrochemistry 13:
62
[19] El-Awady AA, Abd-El-Nabey BA, Aziz SG, Khalifa M, Al-Ghamedy HA (1990) International J
Chem 1: 169
[20] El-Awady AA, Abd-El-Nabey BA, Aziz SG (1992) Electrochem Soc 139: 2149
[21] El-Dakar N, Nobe K (1981) Corrosion 33: 271
[22] Zuman P (1967) Substituent Effect in Organic Polarography. Plenum Press, New York
[23] Rudresh HB, Mayanna SM (1979) Corros Sci 19: 361
[24] Jesionek M, Szklarska-Smialowska I (1983) Corros Sci 23: 183
Hydantoin Derivatives as Corrosion Inhibitors 257
14. [25] Madkour LH, Elmorsi MA, Ghoneim MM (1995) Monatsh Chem 126: 1087
[26] Madkour LH, Ghoneim MM (1997) Bulletin of Electrochemistry 13: 1
[27] Stella V, Highuchi T (1937) J Org Chem 38: 1527
[28] Read WT (1922) J Amer Soc 44: 1766
[29] Hazard R, Cheymol J, Chabrier P (1950) Fr Pat 966, 395; CA (1952) 46(15): 7587b
[30] Mylius F (1922) Z Metallkunde 14: 233
[31] Mylius F (1924) Z Metallkunde 16: 81
[32] Fouda AS, El-Asmy AA (1987) Monatsh Chem 118: 709
Received June 5, 2000. Accepted (revised) September 13, 2000
258 L. H. Madkour et al.: Hydantoin Derivatives as Corrosion Inhibitors