Schiff bases of ethylenediamine as corrosion inhibitors of zinc in sulphuric acid

The work described here deals with the performance of ethylenediamine N,N^′-dibenzylidene, ethylenediamine N,N^′-di(p-methoxybenzylidene), ethylenediamine N,N^′-disalicylidene as corrosion inhibitors for zinc in sulphuric acid. The effect of various parameters on the efficiency of these inhibitors has been studied. Ethylenediamine N,N^′-di(p-methoxybenzylidene) and ethylenediamine N,N^′-disalicylidene give 99% protection under a variety of conditions. Activation energies in the presence and absence of inhibitors have been calculated. It appears that an efficient inhibitor is characterized by a relatively greater decrease in free energy of adsorption, relatively lower entropy of adsorption and relatively lower heat of adsorption. Galvanostatic polarisation studies indicate that these are basically cathodic inhibitors. Cathodic protection in the presence of these inhibitors has been studied. With an efficient inhibitor, cathodic protection is achieved at potentials much less negative than that required for plain acid. The difference between protective potential and corrosion potential appears to be less for an effective inhibitor. Mechanism of the action of inhibitors has been provided.     

Electrochemical behaviour of carbon steel in acid chloride solution in the presence of dodecyl cysteine hydrochloride self-assembled on gold nanoparticles

In this work, the dodecyl cysteine hydrochloride surfactant was synthesized. The surface properties of this surfactant were studied using surface tension technique. The nanostructure of this surfactant with the prepared gold nanoparticles was investigated using TEM technique. The synthesized surfactant and its nanostructure with the prepared gold nanoparticles were examined as non-toxic corrosion inhibitors for carbon steel in 2 M HCl solution using potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The results show that the percentage inhibition efficiency (η%) for each inhibitor increases with increasing concentration until critical micelle concentration (CMC) is reached. The maximum inhibition efficiency approached 76.6% in the presence of 175 ppm of dodecyl cysteine and 90.8% in the presence of the same concentration of dodecyl cysteine hydrochloride self-assembled on gold nanoparticles. Polarization data indicate that the selected additives act as mixed type inhibitors. The slopes of the cathodic and anodic Tafel lines (β_c and β_a) are approximately constant and independent of the inhibitor concentration. Analysis of the impedance spectra indicates that the charge transfer process mainly controls the corrosion process of carbon steel in 2 M HCl solution both in the absence and presence of the inhibitors. Adsorption of these inhibitors on carbon steel surface is found to obey the Langmuir adsorption isotherm. From the adsorption isotherms the values of adsorption equilibrium constants (K_ads) were calculated. The relatively high value of (K_ads) in case of dodecyl cysteine hydrochloride self-assembled on gold nanoparticles reveals a strong interaction between the inhibitor molecules and the metal surface.     

The corrosion inhibitory property of N,N‐bis(2‐benzimidazolylmethyl)amine for Q235 steel

The main purpose of this paper is to systematically evaluate the anti‐corrosion property of N,N‐bis(2‐benzimidazolylmethyl)amine (IDB), which is a novel good thermal stabilized inhibitor in acidic medium. Results obtained from electrochemical tests and corrosion surface morphology analyses reveal that IDB performs excellently as corrosion inhibitor for Q235 steel in 1 mol/L hydrochloric acid corrosive solution. Potentiodynamic polarization measurements show that IDB inhibits both the anodic and cathodic processes of corrosion and exhibits as a mixed‐type inhibitor. Besides, the inhibiting efficiency (IE%) and consequently the degree of surface coverage (θ) increase with the inhibitor concentration rising. And when the concentration is 20 × 10^?5 mol/L, the corrosion inhibition effect is best to reach 96.39%. The adsorption of inhibitor on Q235 steel is found to obey the Langmuir adsorption isotherm, and the calculated Gibbs free energy demonstrates that IDB spontaneously adsorbs and forms a protective chemisorbed film on Q235 steel to restrain its corrosion. Hereby, IDB will become a promising corrosion inhibitor in further.     

Curcumin Derivatives as Green Corrosion Inhibitors for α-Brass in Nitric Acid Solution

1,7-Bis-(4-hydroxy-3-methoxy-phenyl)-hepta-1,6-diene-4-arylazo-3,5-dione I-V have been investigated as corrosion inhibitors for ??-brass in 2?M nitric acid solution using weight-loss and galvanostatic polarization techniques. The efficiency of the inhibitors increases with the increase in the inhibitor concentration but decreases with a rise in temperature. The conjoint effect of the curcumin derivatives and KSCN has also been studied. The apparent activation energy (E _a*) and other thermodynamic parameters for the corrosion process have also been calculated. The galvanostatic polarization data indicated that the inhibitors were of mixed-type, but the cathode is more polarized than the anode. The slopes of the cathodic and anodic Tafel lines (b _c and b _a) are maintained approximately equal for various inhibitor concentrations. However, the value of the Tafel slopes increases together as inhibitor concentration increases. The adsorption of these compounds on ??-brass surface has been found to obey the Frumkin??s adsorption isotherm. The mechanism of inhibition was discussed in the light of the chemical structure of the undertaken inhibitors.     

Corrosion inhibition and adsorption behavior of <Emphasis Type="Italic">Murraya koenigii</Emphasis> extract for corrosion control of aluminum in hydrochloric acid medium

The corrosion behavior of aluminum in the hydrochloric acid medium of pH 3 was studied using Tafel polarization and electrochemical impedance spectroscopy techniques in the presence or the absence of the Murraya koenigii (commonly known as curry) leaves extract at 303 K to 323 K. The concentration of the inhibitor used was in a range of 0.05–0.4 gL^?1. The inhibition efficiency was found to increase with increasing the inhibitor concentration and decreasing temperature. Polarization data showed that the curry leaves extract (CLE) acted as anodic type of inhibitor at lower concentrations of the inhibitor and as mixed type at higher concentrations of the inhibitor. The maximal inhibition efficiency of 91.79% was obtained with the CLE at its optimum concentration of 0.4 gL^?1. Adsorption of the CLE was found to obey the Langmuir adsorption isotherm and underwent both physisorption and chemisorption process. The kinetic and thermodynamic parameters were calculated and discussed in detail. The results obtained by both methods were in good agreement with each other. The protective film formed on the surface of aluminum by the adsorption of inhibitor molecules present in the CLE in the hydrochloric acid medium of pH 3 was confirmed by the scanning electron microscopy and energy-dispersive X-ray spectroscopy. So, the CLE emerged as a potential, cost-effective and eco-friendly natural inhibitor for the corrosion control of aluminum in the hydrochloric acid medium.     

Co‐effect of bis(cyclohexanone) oxalyldihydrazone and copper(II) ion on the corrosion of cold rolled steel in 0.5 M hydrochloric acid solution

Effects of bis(cyclohexanone) oxalyldihydrazone (BCO) and copper(II) ion (Cu²⁺) on the corrosion of cold rolled steel (CRS) in 0.5 M hydrochloric acid (HCl) solution were investigated using Tafel polarization curve and electrochemical impedance spectroscopy (EIS) at 20 °C. Results elucidate that the inhibition efficiency increases with increase in BCO concentration, and the addition of 10^?5 M Cu²⁺ significantly enhances the inhibition efficiency of BCO. Polarization curve results elucidate that the single BCO acts as a mixed‐type inhibitor while the combination of Cu²⁺ and BCO acts as cathodic inhibitor. Ultraviolet and visible spectrophotometer (UV–Vis) results show that BCO molecules do not interact with Cu²⁺ and Fe²⁺ in 0.5 M HCl solution. Atomic force microscope (AFM) result indicates that a protective layer forms on CRS surface after immersion in 0.5 M HCl containing BCO in the absence and presence of Cu²⁺. The adsorption of BCO is found to follow the Langmuir adsorption isotherm in the presence and absence of Cu²⁺. The mechanism of typically chemical adsorption is proposed via the value of free energy of adsorption (ΔG) in the presence of BCO and Cu²⁺.     

The inhibition effect of 2,4,6-tris (2-pyridyl)-1,3,5-triazine on corrosion of tin, indium and tin-indium alloys in hydrochloric acid solution

The influence of 2,4,6-tris (2-pyridyl)-1,3,5-triazine (TPTZ) on the corrosion of tin, indium and tin-indium alloys in 0.5 M HCl solution at different temperatures was studied. Potentiodynamic cathodic polarization and extrapolation of cathodic and anodic Tafel lines techniques were used to obtained experimental data. In the case of tin, the percent inhibition efficiency (IE%) increases as both concentration of TPTZ and temperature are increased. The value of activation energy (E_a) is smaller in the presence of TPTZ than that in uninhibited solution, and decreases with increasing the concentration. However, the effect of TPTZ on indium and the investigated alloys exhibited similar behavior; so, the maximum inhibition efficiency is observed at lowest concentration (10⁻⁶ M) of TPTZ. Then, the value of inhibition efficiency starts to decrease gradually with increasing TPTZ concentration than that of 10⁻⁶ M. But at higher concentration (10⁻³ M) the corrosion current density (I_corr) is still lower than that in uninhibited solution. SEM photographs support that the higher inhibition efficiency is observed at 10⁻⁶ M of TPTZ.The plots of ln K versus 1/T in the presence of the TPTZ in the case of tin, the inhibitor showed linear behavior. The standard enthalpy, ΔH°_ads., entropy, ΔS°_ads. and free energy changes of adsorption ΔG°_ads. were evaluated using Frumkin adsorption isotherm.     

Electrochemical and theoretical investigation on the corrosion inhibition of mild steel by thiosalicylaldehyde derivatives in hydrochloric acid solution

Inhibitory effect of three Schiff bases 2-{[(2-sulfanylphenyl)imino]methyl}]phenol (A), 2-{[(2)-1-(4-methylphenyl)methylidene]amino}-1-benznethiol (B), and 2-[(2-sulfanylphen-yl)ethanimidoyl)]phenol (C) on corrosion of mild steel in 15% HCl solution has been studied using weight loss measurements, polarization and electrochemical impedance spectroscopy (EIS) methods. The results of the investigation show that the compounds A and B with mean efficiency of 99% at 200 mg/L additive concentration have fairly good inhibiting properties for mild steel corrosion in hydrochloric acid, and they are as mixed inhibitor. All measurements show that inhibition efficiencies increase with increase in inhibitor concentration. This reveals that inhibitive actions of inhibitors were mainly due to adsorption on mild steel surface. Adsorption of these inhibitors follows the Langmuir adsorption isotherm. Thermodynamic adsorption parameters (K_ads, ΔG_ads) of studied Schiff bases were calculated using the Langmuir adsorption isotherm. Activation parameters of the corrosion process such as activation energies, E_a, activation enthalpies, ΔH^∗, and activation entropies, ΔS^∗, were calculated by the obtained corrosion currents at different temperatures. Obvious correlation was found between the corrosion inhibition efficiency and the calculated parameters. The obtained theoretical results have been adapted with the experimental data.     

Synergistic inhibition effect of rare earth cerium(IV) ion and sodium oleate on the corrosion of cold rolled steel in phosphoric acid solution

The synergistic inhibition effect of rare earth cerium(IV) ion (Ce⁴⁺) and sodium oleate (SO) on the corrosion of cold rolled steel (CRS) in 3.0 M phosphoric acid (H₃PO₄) has been investigated by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscope (SEM) methods. The results reveal that SO has a moderate inhibitive effect and its adsorption obeys Temkin adsorption isotherm. Ce⁴⁺ has a poor effect. However, incorporation of Ce⁴⁺ with SO improves the inhibition performance significantly, and exhibits synergistic inhibition effect. SO acts as a cathodic inhibitor, while SO/Ce⁴⁺ mixture acts as a mixed-type inhibitor.     

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.     

Kinetic and thermodynamic studies of AISI 4130 steel alloy corrosion in ethylene glycol-water mixture in presence of inhibitors

The electrochemical behavior of steel alloy in ethylene glycol-water mixture was investigated by electrochemical methods. The results obtained showed that corrosion rate was decreased with increasing ethylene glycol concentration. The effect of inorganic inhibitors including NO₃ ^?, NO₂ ^?, Cr₂O₇ ^2? and CrO₄ ^2? were studied using electrochemical techniques where the highest inhibition efficiency was obtained for CrO₄ ^2?. In the presence of chromate the inhibitor efficiency increased with its concentration. The inhibiting effect of the chromate was explained on the basis of the competitive adsorption between the inorganic anions and the aggressive Cl^? ions, and the adsorption isotherm basically obeys the Langmuir adsorption isotherm. Thermodynamic parameters for steel corrosion and inhibitor adsorption were determined and reveal that the adsorption process is spontaneous. Also, a phenomenon of both physical and chemical adsorption is proposed.     

Defect characterization of highly emissive para-phenylene-type molecular films by photoluminescence-detected magnetic resonance and thermally stimulated charge transport

A new combined photoluminescence-detected magnetic resonance (PLDMR) and thermally stimulated current (TSC) study of defects in wide bandgap amorphous methyl-substituted ladder-type poly(para-phenylene) (m-LPPP) and polycrystalline para-hexaphenyl (PHP) films, both with PL quantum yields of ∼30%, is described. As TSC probes the density of mobile charge carriers after detrapping and PLDMR reveals the influence of trapped charges on the PL, their combination yields the concentration of traps, their energetic position, and their contribution to PL quenching. The TSC measurements reveal trap densities≥1.6×10¹⁶ and 1.4×10¹⁴ cm⁻³ for m-LPPP and PHP, respectively. From a comparison of the PLDMR and TSC results one finds that the interaction and hence the nonradiative quenching of singlet excitons at polarons is stronger in PHP than in m-LPPP due to a higher diffusivity of singlet excitons in PHP. Furthermore we show that PLDMR results are in agreement with photoinduced absorption results of pristine and photo-oxidized m-LPPP.     

Electrochemical investigation of inhibitory of new synthesized 3-(4-iodophenyl)-2-imino-2,3-dihydrobenzo[<Emphasis Type="Italic">d</Emphasis>]oxazol-5-yl 4-methylbenzenesulfonate on corrosion of al in acidic medium

3-(4-Iodophenyl)-2-imino-2,3-dihydrobenzo[d]oxazol-5-yl 4-methylbenzenesulfonate (4-IPhOXTs) was synthesized and its inhibiting action on the corrosion of Aluminum 1005 in sulfuric acid was investigated by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results of the investigation show that this compound has excellent inhibiting properties for Al corrosion in sulfuric acid. Inhibition efficiency increases with increase in the concentration of the inhibitor. The adsorption of 4-IPhOXTs onto the Al surface followed the Langmuir adsorption model with the free energy of adsorption ΔG_ads⁰ of?9.18 kJ mol^–1. Quantum chemical calculations were employed to give further insight into the mechanism of inhibition action of 4-IPhOXTs.     

O,O'-二(2-苯乙基)二硫代磷酸二乙铵在HCl溶液中对Q235钢的缓蚀性研究

合成了一种新型缓蚀剂O,O'-二(2-苯乙基)二硫代磷酸二乙铵(EPP),并用元素分析和红外光谱对其进行了表征。采用静态失重法、极化曲线法和电化学阻抗法研究了EPP在HCl溶液中对Q235钢的缓蚀性能,探讨了其在Q235钢表面的吸附行为,考察了HCl浓度、腐蚀体系温度等因素对其缓蚀率的影响。结果表明:EPP是一种高效的混合型缓蚀剂,其缓蚀率随缓蚀剂浓度增加而增大,随腐蚀系统温度升高而缓慢减小。在30℃,1.0 mol·L-1的HCl溶液中,EPP浓度为60 mg·L-1时,其缓蚀率高达98.48%。EPP在Q235钢表面的吸附符合Langmuir吸附等温式,属于自发进行的化学吸附。量子化学计算结果表明,EPP通过配位键和反馈键与金属Fe形成了多中心、稳定的化学吸附。     

The inhibitive effect of 5‐amino‐indole on the corrosion of mild steel in acidic media

The inhibitor performance of 5‐aminoindole (5‐AI) on mild steel corrosion in 0.5 M HCl was investigated in relation to the inhibitor concentration using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and linear polarization (LPR) methods. The effect of immersion time on the corrosion behavior of mild steel was also studied. The impedance data obtained were fitted and modeled using an equivalent circuit model. The results show that 5‐AI is an effective inhibitor and has an inhibition efficiency of 90% at 1 × 10^?2 M additive concentration. The adsorption behavior of 5‐AI was also investigated. For this purpose, the adsorption equilibrium constant (K_ads), and the free energy of adsorption (ΔG_ads) were calculated and discussed. It was found that 5‐AI acts as mixed‐type inhibitor and obeys Langmuir adsorption isotherm with a free energy of adsorption of ?27.71 kJ/mol.     

Synergism between protocatechualdehyde and rare earth cerium(IV) ion on the corrosion of cold rolled steel in hydrochloric acid solution

The synergism between protocatechualdehyde (PAL, 3,4‐dihydroxy‐benzaldehye) and rare earth cerium(IV) ion (Ce⁴⁺) on the corrosion of cold rolled steel (CRS) in 1.0 M hydrochloric acid (HCl) solution has been investigated by weight loss and potentiodynamic polarization methods. The results reveal that PAL has a moderate inhibitive effect, while Ce⁴⁺ has a poor effect. Incorporation of PAL with Ce⁴⁺ improves the inhibition performance significantly, and exhibits synergistic inhibition effect. The adsorption of individual PAL obeys the Temkin adsorption isotherm, and the adsorption of the complex of PAL and Ce⁴⁺ accords with the Temkin adsorption isotherm too. The thermodynamic parameters of adsorption heat (ΔH⁰), adsorption free energy (ΔG⁰), and adsorption entropy (ΔS⁰) are calculated and discussed. Polarization curves show that individual PAL acts as a mixed‐type inhibitor, while Ce⁴⁺ slightly inhibits the corrosion reaction. The complex of PAL and Ce⁴⁺ acts as a mixed‐type inhibitor, which drastically inhibits both anodic and cathodic reactions. Depending on the results, the synergism mechanism is proposed from the viewpoint of adsorption theory.     

Corrosion inhibition of mild steel by polyhydric alcohol phosphate ester (PAPE) in natural sea water

Abstract

The corrosion inhibition of mild steel by polyhydric alcohol phosphate ester (PAPE) in natural sea water has been investigated by polarisation curves, electrochemical impedance spectroscopy (EIS) and surface analytical techniques. The results have shown that PAPE acts as a mixed type (anodic and cathodic) negative catalytic effect interface inhibitor and that the adsorption is of the Langmuir type. The inhibitor can adsorb immediately and compactly on the steel surface, the thickness of the film increasing with time. The adsorption behaviour involves the formation of complexes between the R1 functional group of the PAPE molecular structure and metal ions on the steel surface, such as Fe²⁺, Mg²⁺, Ca²⁺, etc.     

Inhibitory action of aqueous coffee ground extracts on the corrosion of carbon steel in HCl solution

The effects of aqueous extracts of spent coffee grounds on the corrosion of carbon steel in a 1 mol L⁻¹ HCl were examined. Two methods of extraction were studied: decoction and infusion. The inhibition efficiency of C-steel in 1 mol L⁻¹ HCl increased as the extract concentration and temperature increased. The coffee extracts acted as a mixed-type inhibitor with predominant cathodic effectiveness. In this study, the adsorption process of components of spent coffee grounds extracts obeyed the Langmuir adsorption isotherm. The chlorogenic acids isolated do not seem to explain the corrosion inhibition observed during the use of the coffee extracts.     

Inhibition of pure iron by new synthesized tripyrazole derivatives in HCl solution

Inhibitory effect of some new synthesized tripyrazole compounds on corrosion of pure iron in 1 M HCl solution has been studied using weight-loss measurements and various electrochemical techniques polarization and impedance spectroscopy methods. The inhibiting action is more pronounced with N,N,N-tris[(3,5-dimethyl-1H-pyrazol-1-yl)methyl] amine (P1), and its inhibition efficiency increases with its concentration and attains the maximum value of 94% at the 2.5 × 10⁻⁴ M. The effect of temperature on the corrosion behaviour of iron was studied in the range from 298 to 353 K with and without P1 at 2.5 × 10⁻⁴ M. We note a good agreement between gravimetric and electrochemical methods potentiodynamic polarization and impedance spectroscopy (EIS). Polarization measurements show also that the compound acts mixed inhibitor. The catholic curves indicate that the reduction of proton at the pure iron surface happens within a pure activating mechanism. EIS measurements show the increase of the transfer resistance with the inhibitor concentration. The presence of the N,N,N-tris[(3,5-dimethyl-1H-pyrazol-1-yl)methyl] amine increases the inhibition efficiency and not caused a drastic change in its adsorption mechanism. The adsorption of P1 on the surface of iron in 1 M HCl obeys a Langmuir isotherm adsorption.     

氨基硫脲对锌在氯化铵介质中的缓蚀作用及其吸附行为

采用失重，腐蚀电位测试，交流阻抗等方法研究了氨基硫脲对锌在２６％氯化铵介质中的缓蚀作用机理，研究结果表明，ＴＳＣ对锌在氯化铵中的腐蚀有较好的抑制作用，其作用机制为几何覆盖效应。ＴＳＣ在锌表面的吸附近似符合Ｌａｎｇｍｕｉｒ等温式。