Copper corrosion inhibition by triphenylmethane derivatives in sulphuric acid media

Triphenylmethane derivatives, namely fuchsin basic (FB) and fuchsin acid (FA), were studied for their possible use as copper corrosion inhibitors in 0.001 to 1.0 M sulphuric acid solutions. Benzotriazole (BTA) was also tested for comparative purposes. These inhibitors were studied in concentrations from 1×10⁻⁵ to 1×10⁻¹ M at temperatures from 298 to 328 K. The gravimetric method was employed to study the protective effect of FB, FA and BTA. The order of inhibition efficiency was BTA>FB>FA. Up to nine adsorption isotherms were tested to fit the experimental data. The best fit was obtained using the Frumkin isotherm model. A thermodynamic/kinetic model of adsorption was also fitted. The projected molecular area of the inhibitors was calculated to elucidate inhibitor orientation in the adsorption process.     

Copper corrosion inhibition by fast green,fuchsin acid and basic compounds in citric acid solution

Fast green (FG), fuchsin basic (FB) and fuchsin acid (FA) were studied as copper corrosion inhibitors in citric acid solution. Five citric acid concentrations were tested from 0.001 to 1.0 M. Twelve FG, FB and FA concentrations were studied from 1 × 10^?5 to 1 × 10^?1 M, at four temperatures from 298 to 328 K. The gravimetric method was employed to study the protective effect of FG, FB and FA. The order of inhibition efficiency was FB > FA > FG. Conventional adsorption isotherms were tested to fit the experimental data. The best fit was obtained using the Frumkin isotherm model. A thermodynamic/kinetic model of adsorption was also fitted. The projected molecular area of the inhibitors was calculated to elucidate inhibitor orientation in the adsorption process.     

Effect of temperature on the inhibition of the acid corrosion of steel by benzimidazole derivatives

The effect of 2-mercaptobenzimidazole (inh. I) and 2-mercapto-5-methylbenzimidazole (inh. II) on the corrosion of mild steel in 1M solutions of sulphuric acid has been investigated in relation to the concentration of the inhibitor as well as temperature by various monitoring corrosion techniques. The results obtained revealed that these compounds are good inhibitors. All the impedance diagrams gave semicircles for both inhibitors indicating that the corrosion of mild steel is controlled by a charge transfer process and the presence of either inhibitor does not alter the mechanism of the dissolution of mild steel. In general, both inhibitors efficiencies increased with increasing the inhibitors concentration at all temperatures used. On the other hand, inhibitors efficiencies were almost constant with increasing the temperature at concentrations 5 × 10⁻⁴ M, 1 × 10⁻³ M and 5 × 10⁻³ M. The best performance was noticed in case of (inh. II) especially at the concentration 5 × 10⁻³ M. Adsorption of both inhibitors was found to follow Langmuir, Flory-Huggins isotherms and kinetic-thermodynamic model. The binding constants “K” were calculated for both inhibitors. On increasing the temperature, the value of “K” increased in both cases indicative of stronger binding of the inhibitor molecule to the mild steel surface and hence higher inhibition efficiency at higher temperatures. The activation energy of the corrosion reaction decreases with increasing the concentration of (inh. I) or (inh. II). The adsorption of both inhibitors on the surface of mild steel is probably chemisorbed on the electrode surface. The thermodynamic parameters were calculated. Mass loss measurements revealed that both inhibitors exhibit maximum inhibition efficiency with increasing the concentration and temperature which confirm the data obtained from AC impedance. DC polarization data reveals that, both inhibitors does not alter the mechanism of anodic behaviour of mild steel and they behave as mixed type inhibitors. Again both inhibitors exhibit maximum inhibition efficiency with increasing the concentration and temperature which confirm the data obtained from AC impedance.     

Effect of temperature and fluid velocity on corrosion mechanism of low carbon steel in presence of 2-hydrazino-4,7-dimethylbenzothiazole in industrial water medium

The corrosion inhibition of 2-hydrazino-4,7-dimethylbenzothiazole on low carbon steel in industrial water has been investigated at different temperatures and fluid velocities at different concentrations of the inhibitor using mass loss, potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The results showed that corrosion resistance increased by increasing the inhibitor concentration. Optimization of the three variables has been made and correlating the results obtained using Box–Wilson statistical method. The adsorption process on low carbon steel surface obeys Flory–Huggins isotherm. The values of ΔG_ads obtained suggest that, the adsorption process of 2-HMBT on low carbon steel is chemisorption. The activation energy increased with increasing the concentration of inhibitors leading to decrease of the pre-exponential factor, and the entropy of activation increased negatively in the presence of inhibitor. SEM was used to identify the film formed on the metal surface.     

Benzimidazole and its derivatives as corrosion inhibitors for mild steel in 1M HCl solution

In this paper, the inhibition ability of benzimidazole and its derivatives against the corrosion of mild steel in 1M HCl solution was studied. The change of impedance parameters observed by variation of inhibitors concentration within the range of 50-250 ppm was an indication of their adsorption. The thermodynamic adsorption parameters proposed that these inhibitors retard both cathodic and anodic processes through physical adsorption and blocking the active corrosion sites. The adsorption of these compounds obeyed the Langmuir’s adsorption isotherm. The inhibition efficiency was increased with inhibitor concentration in the order of 2-mercaptobenzimidazole > 2-methylbenzimidazole > benzimidazole, which is in accordance with the variation of apparent activation energy of corrosion.     

Cloud point extraction and flame atomic absorption spectrometry analysis of palladium, platinum, and gold ions from industrial polluted soil

Cloud point extraction (CPE) with Tergitol TMN-6 was applied for the extraction of trace amounts of palladium (Pd(Ⅱ)),platinum (Pt(Ⅳ)),and gold (Au(Ⅲ)) in the soil of industrial sewage.Ammonium pyrolysine dithiocarbamate (APDC) was adopted as the chelating agent prior to CPE and then was detected by atomic absorption spectrometry (AAS).Different parameters such as the concentration of surfactants,chelating agent and salt,sample pH,equilibration temperature and time,centrifugation time and rates,and the effect of foreign ions were studied.Under optimum conditions,the low limits of detections are 1.4,2.8 and 1.2 ng.ml-1 and the enrichment factors are 21,12,and 24 for Pd(Ⅱ),Pt(Ⅳ),and Au(Ⅲ),respectively.The relative standard deviations vary from 0.6％ to 1.0％ (n=11).All correlation coefficients of the calibration curves are ＞0.9960.The proposed method was successfully applied for the determination of Pd(Ⅱ),Pt(Ⅳ),and Au(Ⅲ) in the real soil of industrial sewage samples.     

On the inhibition of mild steel corrosion by 4-amino-5-phenyl-4H-1, 2, 4-trizole-3-thiol

The corrosion inhibition of mild steel in a 2.5 M H₂SO₄ solution by 4-amino-5-phenyl-4H-1, 2, 4-trizole-3-thiol (APTT) was studied at different temperatures, utilising open circuit potential, potentiodynamic and impedance measurements. The results indicate that APTT performed as an excellent mixed-type inhibitor for mild steel corrosion in a 2.5 M H₂SO₄ solution and that the inhibition efficiencies increased with the inhibitor concentration but decreased proportionally with temperature. The kinetic and thermodynamic parameters for adsorption of APTT on the mild steel surface were calculated. A chemisorption mechanism of APTT molecules on the mild steel surface was proposed based on the thermodynamic adsorption parameters.     

A comparative study of the corrosion inhibition of mild steel in sulphuric acid by 4,4-dimethyloxazolidine-2-thione

The corrosion protection of mild steel in a 2.5 M H₂SO₄ solution by 4,4-dimethyloxazolidine-2-thione (DMT) was studied at different temperatures by measuring changes in open circuit potential (OCP), potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS). Corrosion current densities calculated from EIS data were comparable to those obtained from polarisation measurements. Results showed that DMT inhibited mild steel corrosion in a 2.5 M H₂SO₄ solution and indicated that the inhibition efficiencies increased with the concentration of inhibitor, but decreased proportionally with temperature. Polarisation curves showed that DMT is a mixed-type inhibitor. Changes in impedance parameters suggested the adsorption of DMT on the mild steel surface, leading to the formation of protective films. The DMT adsorption on the mild steel surface followed the Langmuir adsorption isotherm. The kinetic and thermodynamic parameters for dissolution and adsorption were investigated. Comprehensive adsorption (physisorption and chemisorption) of the inhibitor molecules on the mild steel surface was suggested based on the thermodynamic adsorption parameters.     

Inhibition of the corrosion of steel in hydrochloric acid solution by some organic molecules containing the methylthiophenyl moiety

The corrosion inhibition effect of 2-[4-(methylthio) phenyl] acetohydrazide (HYD), 2-{[4-(methylthio) phenyl] acetyl} hydrazinecarbothioamide (TAD) and 5-[4-(methylthio) benzyl]-4H-1,2,4-triazole-3-thiol (TRD) on steel in 1.0 M HCl was investigated by mass loss and electrochemical methods. The effect of concentration, temperature and immersion time was studied. The results indicated that the compounds are efficient, mixed type and pursue Flory–Huggins adsorption isotherm. The inhibition efficiency at lower concentration of inhibitor decreased with temperature while at higher concentration, it is retained and the calculated free energy attributes this to comprehensive adsorption. The efficiency stands in the order TRD > TAD > HYD and is confirmed by the Quantum studies.     

Effect of inorganic inhibitors on the corrosion behavior of 1018 carbon steel in the LiBr + ethylene glycol + H2O mixture

The effect of inorganic inhibitors on the corrosion behavior of 1018 carbon steel in the mixture LiBr (55%) + ethylene glycol + H₂O at room temperature has been evaluated. Used inhibitors included LiNO₃ (Lithium Nitrate), Li₂MoO₄ (Lithium Molybdate) and Li₂CrO₄ (Lithium Chromate) at concentrations of 5, 20 and 50 ppm. Electrochemical techniques included potentiodynamic polarization curves, electrochemical noise resistance (EN) and electrochemical impedance spectroscopy (EIS) measurements. Additionally, adsorption isotherms were calculated. The results obtained showed that both, the corrosion rate and the passive current density decreased with inhibitors, and, in general terms, inhibitors efficiency increased with inhibitor concentration, except in the case of Li₂CrO_4, where the highest efficiency was obtained with 20 ppm of inhibitor. Pitting potential with 5 ppm of inhibitor, regardless its chemical composition, was more active than in absence of inhibitor, increased at 20 ppm, especially with Li₂CrO₄, and remained unaltered with 50 ppm. EN measurements showed that at 5 ppm of inhibitor, the number of film rupture/repassivation events was higher than that obtained at 20 or 50 ppm. Adsorption isotherms suggested a different adsorption mechanism for each inhibitor, whereas EIS results suggested that the corrosion process when nitrates were added was under charge transfer control, but in the case of molybdates or chromates was under diffusion control.     

Preparation of conductive wool fabrics and adsorption behaviour of Pd (II) ions on chitosan in the pre-treatment

In this study, an effective deposition of Ni–P alloy on wool fabric is proposed by a chemical plating approach with PdCl₂ solution and a carrier agent chitosan (CTS). CTS possesses strong ability to absorb metal ions through several mechanisms, such as electrostatic attraction and chelation, depending on the pH of the solution. The lowest surface resistance of the wool fabric is achieved when Pd (II) ions are absorbed in acid condition (around pH = 2.5). Sorption isotherms are obtained and modeled using Langmuir and Freundlich model and kinetic curves nicely fitted to the pseudo-first-order equation. Also, isotherms have been introduced to obtain the thermodynamic parameters, such as Gibbs free energy, enthalpy and entropy. The resulting positive value of the enthalpy indicates that the adsorption is an endothermic process. Conductive wool fabrics are characterized by scanning electron microscopy (SEM), Fourier transform-infrared (FT-IR) spectroscopy. Evidenced by SEM, CTS–Pd is found on the surface of fabrics and effectively activated the chemical plating. FT-IR shows the adsorption of Pd (II) ions on CTS is mainly controlled by physical adsorption. Mechanical and physical tests were investigated and the encouraging results show no significant modification and open new perspectives for future application of wool fabrics.     

The behaviour of copper-zinc alloys in alkaline solutions upon alternate anodic and cathodic polarization

Galvanostatic cyclic anodic and cathodic polarization curves for four CuZn alloys are traced in alkaline solutions of different concentrations. The anodic behaviour of the first three alloys, with 15.9, 46.8 and 50.5 wt% Zn, resembles that of pure Cu. Oxidation arrests, corresponding to the formation of Cu₂O, Cu(OH)₂, HCuO₂? and Cu₂O₃, are recorded before the evolution of O₂ on the passive electrode. The Zn of the electrodes does not develop its oxidation arrest. It affects, however, the behaviour of the alloys in a number of ways. The results are explained on the basis of kinetic interactions, and in relation to the phase diagram of the Cu-Zn system.The fourth alloy, with 85.9 wt% Zn (ε + η phases), yields upon oxidation in concentrated alkali solutions a series of five or six arrests. The first two of these represent the oxidation of the Zn of the η- and ε-phases, respectively. Calculations have shown that the activity of the Zn in the ε-phase is ～ 4.6 × 10^?10 times that of the free η-phase. The other oxidation steps correspond to the oxidation of the Cu of the alloy. In 0.1N NaOH the same alloy behaves as if it was pure Zn.Critical current densities for the passivation of Cu, Zn and the four alloys are determined in 0.1M Na₂SO₄. The ability of the tested materials to withstand electrochemical dissolution decreases in the succession: Alloy I > Alloy III > Cu > Alloy II > Alloy IV > Zn.     

Kinetic and thermodynamic studies of adsorption of gallium(Ⅲ) on nano-TiO_2

Nano-TiO2 was employed for the adsorption of gallium from aqueous solution in batch equilibrium experiments to investigate its adsorption properties. It was found that the adsorption efficiency of Ga(Ⅲ) was more than 96% at pH 3.0. The adsorption capacities and rates of Ga(Ⅲ) onto nano-TiO2 were evaluated as a function of solution concentration and temperature. The results were analyzed using the Langmuir adsorption isotherms. Adsorption isothermal data could be well interpreted by the Langmuir model. The mean energy of adsorption, 15.81 kJ·mol-1, was calculated from the D-R adsorption isotherm. The kinetic experimental data properly correlate with the pseudo-second-order kinetic model. The thermodynamic parameters for the process of adsorption have been estimated. The △ H Οand △ GΟvalues of gallium(Ⅲ) adsorption on nano-TiO2 showed an endothermic and spontaneous nature of adsorption.     

Tertiary Arsines as Corrosion Inhibitors for Zinc in acid solution

Tertiary arsines such as diphenylethyl arsine (DPEA), diphenylmethyl arsine (DPMA) and triphenyl arsine (TPA) have been used as corrosion inhibitors for zinc in perchloric acid solution. These inhibitors inhibit corrosion effectively even in traces. The percentage inhibitor efficiency of the inhibitors are in the order DPEA > DPMA > TPA. The effect of pH and temperature on the inhibitor efficiency is studied. Steady state anodic and cathodic polarization data reveal that tertiary arsines act as interfacial corrosion inhibitors for zinc in acidic solution. The apparent free energies of adsorption of inhibitors have been reported for different possible modes of adsorption.     

Comment on “Tritium absorption–desorption characteristics of LaNi4.25Al0.75”

The thermodynamic data for LaNi_4.25Al_0.75 tritide, reported by Wang et al. (W.-d. Wang et al., J. Alloys Compd. (2006), doi:10.1016/j.jallcom.206.09.122), are in variance with our published data. The plateau pressures for the P–C–T isotherms at all temperatures are significantly lower than published data. As a result, the derived thermodynamic parameters, ΔH° and ΔS°, are questionable. Using the thermodynamic parameters derived from the data reported by Wang et al. will result in under estimating the expected pressures, and therefore not to provide the desired performance for storing and processing tritium.     

Inhibition effect of nonionic surfactant on the corrosion of cold rolled steel in hydrochloric acid

The inhibition effect of Tween-20 as a nonionic surfactant on the corrosion of cold rolled steel (CRS) in 1.0-8.0 M HCl has been studied at different temperatures (20-50 °C) by weight loss and potentiodynamic polarization methods. Atomic force microscope (AFM) provided the CRS surface conditions. The results show that Tween-20 is a good inhibitor in 1.0 M HCl, and the inhibition efficiency (IE) increases with the inhibitor concentration, while decreases with increasing the hydrochloric acid concentration and temperature. Effect of immersion time was also studied and discussed. The adsorption of inhibitor on the CRS surface obeys the Langmuir adsorption isotherm equation. Both thermodynamic and kinetic parameters have been obtained by adsorption theory and kinetic equations. The inhibition effect is satisfactorily explained by the parameters. Polarization curves show that Tween-20 is a mixed-type inhibitor in hydrochloric acid. The results obtained from weight loss and polarization are in good agreement, and Tween-20 inhibition action could also be evidenced by surface AFM images.     

Schiff bases of increasing complexity as mild steel corrosion inhibitors in 2 M HCl

The effect of three Schiff base compounds with increasing number of coordination sites, namely, 2-{(E)-[(2-hydroxyethyl)imino]methyl} phenol (I), 2-[(E)-({2-[(2-hydroxyethyl)amino]ethyl}imino)methyl]phenol (II) and 2,2′-{iminobis[ethane-2,1-diylnitrilo(E)methylylidene]}diphenol (III) have been investigated at 298 K by weight loss measurements, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The inhibition efficiencies obtained from all methods employed are in good agreement. Results show compound III to be the best inhibitor with a mean efficiency of 93% at 10⁻² M additive concentration. Studies showed all three compounds to act as mixed type inhibitors.     

Comparison of inhibition efficiency of some azoles on corrosion of type 304 stainless steel in acidic solutions

Abstract

Inhibition efficiencies have been investigated for two types of azole, namely 2-mercaptobenzoazole (CBA) and 2-methylbenzoazole (MBA), containing nitrogen, sulphur, oxygen, or selenium atoms, on the corrosion of type 304 stainless steel in 2M sulphuric acid (H₂SO₄) and 3M hydrochloric acid (HCl). The study was conducted using weight loss, gasometry, and polarisation methods. It was shown that some of the compounds tested provide 90% inhibition efficiency at a concentration of 5 × 10^-4M and that the efficiency depends on the heteroatom and decreases in the order Se > S > N > O. These inhibitors were more efficient in H₂SO₄ than in HCl whereas the opposite is true for inhibitors with nitrogen alone. Adsorption isotherms were fitted to the experimental findings and some thermodynamics functions were obtained.     

Effect of substituents on the inhibitive properties of newly synthesized 5-benzoyl-4-methyl-1,3,4,5-tetrahydro-2H-1,5-benzodiazepin-2-one derivatives against mild steel corrosion in an acidic medium

Inhibition performance of three newly synthesized 1,5-benzodiazepine derivatives with 4-methoxybenzoyl (methoxyBBD), 3-methylbenzoyl (methylBBD), and 2-chlorobenzoyl (chloroBBD) groups was investigated against mild steel corrosion in 1 M hydrochloric acid. The potentiodynamic polarization, electrochemical impedance spectroscopy, and adsorption isotherms were used for characterization of the corrosion processes. Surface morphology was studied by scanning electron microscope (SEM). Quantum chemical calculations were carried out to establish the active sites of the inhibitors. The results show that the inhibitors inhibit mild steel corrosion and their inhibition efficiencies (IE) increase with the increase in concentration. The methoxyBBD shows a higher inhibiting effect with IE of 89.13% at 10⁻³ M, followed by methylBBD. All three inhibitors act as mixed-type inhibitors with predominant control of cathodic reaction for chloroBBD and their adsorption obeys Langmuir isotherm. The SEM analysis confirms the inhibitors' adsorption on the mild steel surface. The active sites of the inhibitors were effectively established using the density functional theory method on the basis of natural atomic charge, highest occupied molecular orbital, and the lowest unoccupied molecular orbital frontier molecular orbitals. The experimental and quantum results prove the inhibition performance trend of the inhibitors as follows: methoxyBBD > methylBBD > chloroBBD.     

Molybdate and tungstate as corrosion inhibitors for cold rolling steel in hydrochloric acid solution

The inhibition effects of molybdate and tungstate on the corrosion of cold rolling steel (CRS) in hydrochloric acid solution (0.1-0.5 M) were investigated by weight loss and electrochemistry methods. The results reveal that both molybdate and tungstate are very good inhibitors with little concentration. The adsorption of inhibitors on the CRS surface basically obeys the Langmuir adsorption isotherm equation. The effect of temperature on the corrosion behavior of CRS was also studied at 25 °C and 35 °C, the thermodynamic parameters such as adsorption heat (ΔH⁰) and adsorption free energy (ΔG⁰) were calculated. In the same conditions, a comparative study of corrosion inhibition of molybdate and tungstate indicated that molybdate was the better inhibitor in 0.1 M HCl. However, the value of percentage inhibition efficiency (IE) was dependent on the concentration of inhibitors in 0.2-0.5 M HCl. It seemed that molybdate did not have the strong inhibitive effect compared to tungstate with relatively small concentration of inhibitors, but molybdate was a better inhibitor over a wide concentration range of inhibitors. A kinetic study of cold rolling steel in uninhibited and inhibited acid was also discussed. Various parameters such as rate constant k and the kinetic parameter B were calculated for the reactions of corrosion. Polarization curves showed that both molybdate and tungstate are mixed-type inhibitors in acidic media.