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To produce effective, less expensive molecules with minimum impact on the environment, the study aims to develop green corrosion inhibitors, which can significantly protect mild steel during its pickling and descaling treatment Therefore, the present study describes the corrosion inhibition performance of two thiazole derivatives, namely thiazolidine-2,4-diones and its amino derivative 2-aminothiazolidin-4-one designated as TZD, and AT, respectively mild steel in 5%HCI solution through gravimetric measurement, electrochemical measurement (open circuit potential, electrochemical Impedance Spectroscopy, and potentiodynamic polarization). The spectroscopic measurement like FT-IR, UV-vis, X-ray photoelectron spectroscopy (XPS) along with surface morphological analysis like scanning electron microscopy-energy dispersive spectroscopy (SEMEDS) and atomic force microscopy (AFM) was also carried out. Gravimetric studies suggested that the inhibitory effects of the proposed compounds improves with an increase in the concentration of TZD and AT and solution temperature, having the most significant efficiencies of 98.0% and 99.7%, respectively, at 5 x 10-4 M at 60 °C. According to electrochemical tests, the analyzed inhibitor molecules function as mixed-type corrosion inhibitors and improve corrosion charge transfer resistance. AFM, SEM, and EDS investigations indicated that TZD and AT molecules adhere and construct a surface protective layer. [ABSTRACT FROM AUTHOR]

The 2,2′-bipyridine-3,3′-dicarboxylic acid (bpda) and its transition metal complexes including Ni(bpda)2, Zn(bpda)2 and Mn(bpda)2, were synthesized and tested as corrosion inhibitors for a carbon steel in 0.5 M HCl solution by electrochemical tests and surface analyses. The electrochemical results indicate that the inhibition efficiencies increase with the concentration of corrosion inhibitors. The complexes exhibit higher inhibition efficiencies compared to the bpda ligand, among which Ni(bpda)2 is the most effective for inhibiting corrosion. The corrosion morphology observation further evidences the superior corrosion inhibition performance of the three complexes. Fourier transform infrared and X-ray photoelectron spectroscopy analyses confirm the spontaneous adsorption of all four inhibitors on the steel surface, and the adsorption analysis suggests a combined physisorption and chemisorption mechanism. Accordingly, the superior corrosion inhibition performance of the three complexes could be attributed to their good adsorption abilities. [ABSTRACT FROM AUTHOR]

Because of the long-term interaction with polluted groundwater, the physicomechanical characteristics of rock have deteriorated. In this paper, experimental investigations were conducted to shed light on the effects of acid types, pH values, and immersion periods on physicomechanical properties, microstructure change, and energy characteristics of sandstone. Besides, the essence of mechanical deterioration of corroded sandstone was revealed based on the energy evolution law, and the chemical damage mechanism of sandstone subjected to acid solutions was concluded in the theoretical context of chemical kinetics. The results showed that acid corrosion would cause the increase of P-wave velocity, porosity, peak strain, the decrease of characteristic stresses, elastic modulus, strain energy, and the change of internal microstructure and mineral content. The same exponential function could express the relationship between damage variables based on P-wave velocity or porosity and corrosion time. Moreover, the effects became evident as pH values declined and immersion periods extended, especially for HCl solution. [ABSTRACT FROM AUTHOR]

Corrosion of low-carbon steel St3 in 2 M H2SO4 containing Fe2(SO4)3 was studied by measuring mass loss of the metal samples and using voltammetric measurements on a rotating disk electrode. Corrosion of steel in this medium involves anodic ionization of steel proceeding in the kinetic region and two cathodic partial reactions: hydrogen evolution and reduction of Fe(III) to Fe(II) cations characterized by kinetic and diffusion control, respectively. The potentiometric data measured on a platinum electrode in 2 M H2SO4 containing Fe2(SO4)3 and FeSO4 made it possible to establish that Fe(III) cations are bound in complexes with sulfate anions in these media. The oxidizing ability of a corrosive medium, characterized by the Fe(III)/Fe(II) redox pair potential, depends on the Fe(III) content in it and is well described by the Nernst equation. The diffusion coefficients of Fe(III) cations were determined by cyclic voltammetry on a platinum electrode in 2 M H2SO4 in the presence of Fe(III) and by evaluating the response of the cathodic current of a steel electrode to the convective factor in the same medium. The apparent diffusion coefficient of Fe(III) cations measured on a steel electrode in inhibited media may be significantly lower than that in uninhibited media because the penetration of Fe(III) cation through the protective layer of inhibitor to the metal surface is hindered. The weak inhibition of corrosion of low-carbon steel in H2SO4 solutions containing Fe2(SO4)3 by the composite inhibitors under study is the result of the accelerating action of Fe(III) cations on three partial electrode reactions on the metal surface: reduction of Fe(III) and H+ characterized by diffusion and kinetic control and anodic ionization of iron. [ABSTRACT FROM AUTHOR]

Synergistic effect of KI on the corrosion inhibition efficiency of methylene bis [(2-hydroxy-5, 1-phenylene) bismethylene] tetraphosphonic acid (TPA) on corrosion of copper in 0.5 M HCl have been tested using weight loss, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. The study show that copper is more efficiently inhibited by decreasing the concentration of TPA, and enhancement in inhibition efficiency was observed with an addition of 0.02 M potassium iodide due to synergism. The highest inhibition efficiency of 91% was observed for10−8 M TPA while an addition of 0.02 M KI to 10−8 M TPA improved the inhibition efficiency to 98%. Electrochemical test data prove that they are cathodic inhibitor and exhibit remarkable corrosion inhibition ability. The morphology confirms that the synergistic effect is due to coadsorption of iodide ions and TPA is co-operative in nature. Furthermore, the inhibition efficiency of (TPA + KI) does not depend on temperature. The adsorption of TPA alone or with iodide ions on the metal surface followed Frumkin adsorption isotherm. Thermodynamic parameters (Kads, ΔG°ads, ΔS°ads) were calculated using the adsorption isotherms from temperatures ranging from 25 to 55 °C. The experimental results were confirmed by density functional theory (DFT) and molecular dynamic simulation (MDS) calculation. [ABSTRACT FROM AUTHOR]

The deterioration process and corrosion protective effect of 7B04 aluminum alloy/anodic film/epoxy primer system in acidic NaCl solution for 3024 h were investigated by optical/electron microscopes, electrochemical impedance spectroscopy (EIS), scanning Kelvin probe (SKP), and pull‐off adhesion test. The results showed that the protective system of anodic film and epoxy primer can protect aluminum alloy from pitting corrosion after immersion for 2352 h. According to the response characteristics of EIS and SKP, different stages of the failure process could be identified. During the first 100 h of immersion, the water transport in the coating followed Fickian law, and the water diffusion coefficient was 2.03 × 10−11 cm2/s, which demonstrated that the coating has good impermeability. Anodizing and coating treatment improved the open circuit potential and impedance of 7B04 aluminum alloy and made the distribution of Volta potential more uniform. The decreasing rate of wet adhesion strength was first fast and then slow, which was similar to the variation rule of coating resistance. The anodic film enhanced the adhesion between epoxy primer and substrate so that the failure nature of the adhesion test was mainly the cohesive failure of the epoxy primer. [ABSTRACT FROM AUTHOR]

The inhibition of (3ar,6ar)-3a,6a-di-p-tolyltetrahydroimidazo[4,5-d]imidazole-2,5(1 h,3h)-dithione (TTHIIDT) for carbon steel was full characterized in a 1 M hydrochloride acid environment at various inhibitor concentrations and temperatures by the gravimetric, electrochemical, surface and quantum chemical analyses. The obtained results confirmed that the inhibition efficiency of TTHIIDT was over 95–97% and nearly stable in the rise of temperature and concentration; TTHIIDT was mixed type inhibitor and effectively influenced both anodic and cathodic corrosion reactions; a protective hydrophobic thin layer of this inhibitor on the carbon steel surface is more stable and non soluble in 1 M HCl medium; this inhibitor adsorbed endothermically on the carbon steel surface by the chemical and physical adsorption processes. The quantum chemical calculations supported the experimental results and showed that the inhibition efficiency is depends on the structure of inhibitor.

A combined experimental and theoretical approach has been used to evaluate the corrosion inhibition potential of an ecofriendly, cost effective and benign compound (Aspirin) on mild steel in acidic media using hydrogen evolution technique within a temperature range 303 K–333 K in sulphuric acid solution. The results show that Aspirin inhibits the corrosion of mild steel in acidic media. The inhibition efficiency of Aspirin was found to increase with inhibitor concentration and decreased with rise in temperature. The maximum inhibition efficiency was 79.2 % with 800 mg/L of Aspirin at 333 K. The corrosion reaction kinetics in the presence of Aspirin shows a transition from first order to second order kinetics on going on elevating the temperature of the system. The trend in activation energy, Ea and the enthalpy of activation, ΔH indicate that the corrosion process is endothermic, the entropy of activation, ΔS shows that the process is spontaneous. The experimental results were in consonance with Langmuir isotherm and a physical adsorption mechanism is proposed for the adsorption of inhibitor on the mild steel surface. Complementary information was obtained from theoretical computations which show that the EHOMO and ELUMO for Aspirin are −7.33 eV and −2.06 eV, respectively. Molecular dynamics simulation reveals a strong binding affinity between inhibitor and the steel surface with a binding energy of −117.2 kcal/mol at the most stable adsorption configuration.

Imidazoline obtained from the essential oil contained in Pouteria sapota seed was tested as an environmentally-friendly corrosion inhibitor of 1018 carbon steel in CO2 saturated 3.5 % NaCl solution using electrochemical techniques. This imidazoline contains fatty acids with the presence of long hydrophobic chains, with 52.73 % of unsaturated (oleic and linolenic acids) and 40 % of saturated (palmitic and myristic acids) compounds. Polarization curves revealed that this inhibitor is highly efficient mixed-type of inhibitor with the inhibitor efficiency of 99.9 % reached at 25 ppm. Also, the lowest pitting potential value was observed at 25 ppm of inhibitor, making the carbon steel highly susceptible to the pitting type of corrosion. Corrosion current density value decreased by nearly four orders of magnitude, and a passive film formation was induced for inhibitor concen­tra­tions higher than 5 ppm. Accordingly, polarization resistance values were increased from 100 W cm2 up to about 106 W cm2 at 25 ppm of inhibitor. The inhibitor forms a protective film of corrosion products adsorbed on the metal surface in a very strong chemical way, following a Langmuir type of adsorption isotherm. This was supported by electrochemical impedance spectra that showed two relaxation processes ascribed to electrode interface and film regions. In agre­ement with polarization resistance data, the total electrode resistance determined by inter­facial charge transfer and film resistance, increased up to 8.2 ´ 105 W cm2 in presence of 25 ppm of inhibitor. SEM images additionally showed that type of corrosion was fully changed from uniform to a localized type when 25 ppm of inhibitor was added into the solution.

Underground rock is often subjected to the coupled action of acid sulfate, chloride ion corrosion, and external dynamic disturbance: the degree of corrosion and dynamic load can significantly affect the pore structure and mechanical behavior of rock. To quantify the microscopic pore structure changes and macro-dynamic behavior characteristics of acidified corroded sandstone, first, a mixed acidic solution of NaHSO4 and HCl with different pH values was used for immersion corrosion of sandstone; second, the pore structure of sandstone before and after corrosion was quantitatively evaluated by nuclear magnetic resonance (NMR), dynamic loading tests of corroded sandstone were conducted on an SHPB experimental system and scanning electron microscopy (SEM) was used to observe the morphology of corroded sandstone section; and finally, the mechanism of water–rock interaction and damage and fracture of acid-corroded sandstone were analyzed. The results show that, after acidizing corrosion of sandstone, the macropores increase significantly in number and volume, the boundary of the pore structure tends to be fuzzy; the effective porosity, the number of effective pores, and the total porosity increase significantly; the residual porosity, the number of residual pores, and T2 cut-off value decrease. The proportion accounted for by the elastic stage in stress–strain curves of corroded sandstone is lowered; the proportion accounted for by the plastic yield stage is increased; and post-peak rebound is diminished. With the decrease of pH value, the peak stress on acid-corroded sandstone decreases and the peak strain increases. The peak stress on corroded sandstone is negatively correlated with effective porosity and the number of effective pores, but positively correlated with residual porosity, the number of residual pores, and the T2 cut-off value. The reaction of acidic solution with sandstone minerals causes the free fluid space to increase, the bound fluid space decreases, and the number of pores increases, resulting in a decrease in the dynamic strength of acidified sandstone. The fracture of original sandstone after impact failure has no obvious directionality, and the failure mode of grain is the coexistence of intergranular fracture and trans-granular fracture. The fracture of sandstone after acidizing corrosion is obviously directional after impact damage, and the fracture form is single, which is intergranular fracture. The research results can provide a certain reference for the protection of rock engineering under acidic water chemical environment. [ABSTRACT FROM AUTHOR]

Impedance spectroscopy was used to study the adsorption of the IFKhAN-92 inhibitor, a triazole derivative, on cathodically polarized chromium–nickel steel from 1 M HCl and 2 M H2SO4 solutions (22 ± 1°C). The free energy of the IFKhAN-92 adsorption from the HCl and H2SO4 solutions was found to be (‒ΔGads) = 55 ± 1 and 61 ± 1 kJ/mol, respectively, which made it possible to assume the chemosorption nature of the interaction between the inhibitor and steel surface. The joint adsorption of IFKhAN-92 and anionic additives (KNCS, KI, and KBr) on chromium–nickel steel from the H2SO4 solutions was accompanied by their competition, which reduced the free energy of adsorption of these compounds. Nevertheless, the obtained values of free energy of the components of these mixtures indicated the preservation of their chemosorption interactions with the metal. [ABSTRACT FROM AUTHOR]

The importance of mild steel lies in its industrial applications, and the fight against corrosion is very important from an ecological, economic, technical, and aesthetic view. The current study involves the use of pharmaceutical drugs namely GTN towards corrosion inhibiting reaction was examined by gravimetric and electrochemical approaches. From weight loss studies, maximum I. E (%) 94.04% reached for 60 mg/L concentration of GTN for 6 h immersion time. The Polarization measurements showed that the behaviour of GTN as mixed nature and surface assimilation of GTN at the superficial, such that water molecules are substituted at the solution-metal boundary. The corrosion resistance property of the studied inhibitor as coating was also evaluated in NaCl which shows better progress corrosion retardation property of coating in the saline medium. Theoretical calculations were employed using DFT to correlate with the experimental observations. [ABSTRACT FROM AUTHOR]

The focus of recent research has been the development of organic films on the metal surface to achieve a desirable degree of metal protection. In this respect, more attention has been drawn to environmentally friendly compounds. Pigeon pea seed (PPS) extract is one of the natural and biodegradable compounds with a promising potency for corrosion inhibition. In this work, pigeon pea seed extract inhibited mild steel corrosion in strong acid electrolyte. To evaluate the efficiency and provide well-defined mass transfer operations, electro-kinetics, Tafel polarization, weight loss and molecular dynamics were applied. FTIR, SEM and AFM were employed to characterize the structure and nature of the organic film-based complexes formed on the steel plates. For the statistical analysis, particle swarm optimization (PSO) and response surface methodology (RSM) were used to evaluate the interactive effects between the independent variables and the expected responses. The result from electro-kinetics shows that pigeon pea seed extract is a practical protocol for the improvement of reliable steel corrosion resistance. Polarization measurement showed that due to the formation of the pigeon pea seed extract-based film on the mild steel, a successful corrosion inhibition of steel by a mixed-mode mechanism occurred. PPS exhibited good inhibition nature, and its inhibition efficiency can be as high as 94% when the concentration is 0.9 g/L−1 at temperature of 300 K. The adsorption kinetics adheres strictly to Langmuir model. The DFT studies complement with the experimental data. The MIMO model via RSM gave better prediction than PSO. Results from SEM/AFM photographs and FTIR confirmed that complexes based on the pigeon pea seed extract precipitated a protective film on the steel sample. [ABSTRACT FROM AUTHOR]

Aiming at the acid-etched freeze-thaw rock for geotechnical engineering in cold regions, chemical damage variables, freeze-thaw damage variables, and force damage variables were introduced to define the degree of degradation of rock materials, the law of damage evolution, the total damage variable of acid-corroded rock under the coupling action of freeze-thaw and confining pressure was deduced. The continuous damage mechanics theory was adopted to derive the damage evolution equation and constitutive model of acid-eroded rock under the coupling action of freeze-thaw and confining pressure. The theoretical derivation method was used to obtain the required model parameter expressions. Finally, the model's rationality and accuracy were verified by the triaxial compression test data of frozen-thawed rocks. Comparing the test curve's peak point with the peak point of the model theoretical curve, the results show that the two are in suitable agreement. The damage constitutive model can better reflect the stress-strain peak characteristics of rock during triaxial compression, verifying the rationality and reliability of the model and the method for determining the model parameters. The model extends the damage model of rock under the coupling action of freeze-thaw and confining pressure in the chemical environment and further reveals the damage mechanism and failure law of acid-corroded rock under the coupling action of freeze-thaw and confining pressure. [ABSTRACT FROM AUTHOR]

Corrosion inhibitive action of glutathione reduced (Gth), an eco-friendly inhibitor of aluminium alloy 6061 (AA6061) was investigated in a 0.5 M HCl medium. Experiments were conducted using weight loss and potentiodynamic polarization (PDP) methods. The inhibition efficiency of Gth increases with increasing its concentration and decreases with increasing temperature. Gth demonstrated reasonably good inhibition performance (87 % at 0.7 mM at 303 K) by acting as a mixed inhibitor. The measurement of activation and thermodynamic parameters regulating the inhibition behavior of Gth shows the mixed adsorption of Gth on the alloy surface, which follows the Langmuir isotherm model. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) was used to conduct the surface morphological examination of corroded and inhibited alloy specimens.

The present study aims to explore the effect of 2-nitroacridone, an antimicrobial compound, on low carbon steel (LCS) corrosion in acid solution (1 M HCl). The compound was tested at various concentrations (0.001−10 mM) and five temperatures (25, 35, 45, 55, and 65 °C) to determine the optimal concentration and temperature range for the best corrosion inhibiting effect. In evaluating the inhibition efficiency, weight loss measurement, potentiodynamic polarization measurement, electrochemical impedance spectroscopy, SEM/EDAX/AFM and DFT measurements were used. The inhibition efficiency increases with the increase in concentration and decreases with temperature. The maximum inhibition efficiency was found (94.96%) at 25 °C in the presence of 5 mM concentration of the studied compound. The various adsorption isotherms were also explored to find the best fit, which was found to obey the Langmuir adsorption isotherm. The thermodynamic parameters (Ea, Kads, ΔG°ads) have also been calculated and discussed. The potentiodynamic polarization study revealed that 2-nitroacridone behaved as a mix-type of inhibitor that predominantly inhibited the anodic reaction. Moreover, a correlation between the inhibition efficiency of the studied compound and certain molecular parameters were determined by quantum chemical computations.

Alumina ceramics are widely used because of chemical corrosion resistance. Although alumina ceramics can resist many strong acids and organic acids, be corroded easily by HF due to silicon components in raw materials. This work aimed to reveal the effect of La2O3 on HF/HCl resistance of the alumina ceramic containing SiO2. The X-ray diffractometer (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), were used to study the microstructure and mechanism, acid solubility and bulk density were tested. It was discovered that La caused the enrichment of Ca and Si, and the enrichment degree of Si was higher, which led to generation more CaAl2Si2O8 in the ceramic. Moreover, La3+ could replace Ca2+ to form solid solutions with CaAl2Si2O8. The acid solubility of the solid solutions and La0.85Al11.55O18.6 and the effect of them on the corrosion resistance of this alumina ceramic were studied. Results showed that a proper addition of La2O3 was beneficial to the acid resistance of alumina ceramic for long time corrosion, while bulk density increased. The mechanism of corrosion resistance has been discussed.

Background: The environmental and economic benefits have been the driving force in search of efficient corrosion inhibitors for iron/steel used in industrial acidic medium. This study reports on berberine isolated from methanol extract of high-altitude (1347 m) shrub Mahonia nepalensis as a highly efficient and thermally stable corrosion inhibitor for mild steel (MS) in 1.0 M H2SO4 simulating acid pickling condition. Methods: The weight-loss and electrochemical methods revealed the fast adsorption of berberine.Significant Findings: It achieved above 91% inhibition efficiency (IE) in 0.25 h and reached 94% in 6 h for 1000 ppm berberine. The IE increased with concentration and temperature, giving an IE of 97.2% at 328 K, which makes it a promising candidate for industrial application. It behaved as a mixed type of inhibitor as revealed by open circuit potential and polarization curves. The results indicated suppression of the corrosion by effectively forming an adsorbed berberine layer on the MS surface. Adsorption of the berberine followed a Langmuir adsorption isotherm. The thermodynamic parameters such as activation energy (43.19 kJ/mol), free energy (−35.05 kJ/mol), enthalpy (40.55 kJ/mol), and entropy (−97.83 J/molK) of adsorption supported both physical and chemical interactions of berberine with MS surface. The obtained results also revealed that the adsorption process was endothermic and spontaneous in nature.

The treatment of low-carbon steel items with hydrochloric acid solutions is used in many industrial technologies. This process is accompanied not only by metal corrosion losses, but also by hydrogen absorption by the metal. In this study, the kinetics of hydrogen cathodic reduction on low-carbon steel in 2 M HCl containing corrosion inhibitors, namely, quaternary ammonium salts and a 3-substituted 1,2,4-triazole, have been studied. Adsorption isotherms of corrosion inhibitors on cathodically polarized steel surface have been obtained. XPS data provide valuable information on the composition and structure of protective layers formed on steel in HCl solutions containing inhibitors. The main rate constants of the stages of gaseous hydrogen evolution and incorporation of hydrogen atoms into the metal have been determined. The addition of quaternary ammonium salts or 3-substituted 1,2,4-triazole inhibits the cathodic reduction of hydrogen and its penetration into steel in the HCl solution. 3-substituted 1,2,4-triazole is the most efficient inhibitor of hydrogen absorption. The inhibitory effect of this compound is caused by a decrease in the ratio of the hydrogen concentration in the metal phase to the degree of surface coverage with hydrogen. The maximum decrease in hydrogen concentration in the metal bulk in the presence of the 3-substituted 1,2,4-triazole is 8.2-fold, which determines the preservation of the plastic properties of steel as it corrodes in HCl solutions. The high efficiency of the 3-substituted 1,2,4-triazole as an inhibitor of hydrogen cathodic reduction and absorption results from strong (chemical) adsorption of this compound on the steel surface and the formation of a polymolecular protective layer.

The effect of an aromatic hydrazide derivative 4-hydroxyl-N′-[(3-hydroxy-4-methoxyphenyl) methylidene] benzohydrazide] (HMBH) as inhibitor for the corrosion of carbon steel in 0.5 M H2SO4 solution was investigated in the temperature range of 303 K to 323 K using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). The concentration of HMBH used was in the range of 0.1 to 1 mM. Inhibition efficiency (% IE) increased with increase in concentration of HMBH and decreased with increase in temperature. Maximum % IE obtained was around 71 with 1 × 10-3 M HMBH in 0.5 M H2SO4 at 303 K. The Tafel polarization results indicate that HMBH acted as a mixed type of inhibitor. The results of evaluation of thermodynamic and activation parameters suggest the mixed adsorption of HMBH took place by physisorption, and it obeyed Freundlich's isotherm. Scanning electron microscope (SEM) and atomic force spectroscopy (AFM) images were also recorded to supplement the results of electrochemical studies, and mechanism for corrosion inhibition was suggested. [ABSTRACT FROM AUTHOR]

The effect of an aromatic hydrazide derivative 4-hydroxyl-N′-[(3-hydroxy-4-methoxyphenyl) methylidene] benzohydrazide] (HMBH) as inhibitor for the corrosion of carbon steel in 0.5 M H2SO4 solution was investigated in the temperature range of 303 K to 323 K using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). The concentration of HMBH used was in the range of 0.1 to 1 mM. Inhibition efficiency (% IE) increased with increase in concentration of HMBH and decreased with increase in temperature. Maximum % IE obtained was around 71 with 1 × 10-3 M HMBH in 0.5 M H2SO4 at 303 K. The Tafel polarization results indicate that HMBH acted as a mixed type of inhibitor. The results of evaluation of thermodynamic and activation parameters suggest the mixed adsorption of HMBH took place by physisorption, and it obeyed Freundlich's isotherm. Scanning electron microscope (SEM) and atomic force spectroscopy (AFM) images were also recorded to supplement the results of electrochemical studies, and mechanism for corrosion inhibition was suggested. [ABSTRACT FROM AUTHOR]

This work is a continuation of a series of studies on the preparation of acid corrosion inhibitors derived from carboxylic acids. A synthesis was developed for acid corrosion inhibitors derived from oleic acid amides. Several syntheses were carried out in an attempt to obtain compounds with improved corrosion inhibition properties. Aminoalcohols were added to oleic acid in the first step and the resultant products were sulfated with sulfuric acid. Reactions with bases were carried out with the aim of expanding the range of such inhibitors. Salts of sulfated oleic acid amides were synthesized by reaction with aminoalcohols, sulfuric acid, and bases in aqueous solution. The protective action in dilute hydrochloric acid was evaluated in order to establish the inhibition efficiency of these compounds, some of which appear to have suitable corrosion inhibition properties. The ammonium salt of the sulfated diethanolamide of oleic acid was found to be the most efficient corrosion inhibitor among these products. [ABSTRACT FROM AUTHOR]

Plant-based material, namely bitter kola leaf, as an additive for surface modification of mild steel in H2SO4 solution was thoroughly scrutinized using electrochemical, theoretical and optimization techniques. The functional groups, of the biomolecules of the bitter kola leaf extract, were examined using Fourier transforminfrared spectrometry (FTIR) and gas chromatography-mass spectrophotometry (GC-MS). For clarification purpose, scanning electron microscopy (SEM) was used to inspect the texture of the degraded and inhibited steel after 21 h of immersion. For the response surface methodology (RSM), central composite design of Design-Expert Software was used to optimize the inhibition efficiency as a function of acid concentration, inhibitor concentration, temperature and time. The optimum inhibition efficiency of 93%was obtained at 0.9 g L-1 bitter kola leaf. The mutual correlation between the considered variables and expected response was adequately interpreted by a quadratic model. The fitness of the model was justified by the following standards which include P-value (<0.0001), adjusted R2 (0.9843), R2 (0.991), adequate precision (43.14) and coefficient of variation (2.59). Bitter kola leaf extract behaved as a mixed-type inhibitor and adequately satisfied Langmuir adsorption isotherm. Furthermore, the theoretical modelling revealed the most active molecule of bitter kola leaf responsible for the overall inhibition. The experimental and theoretical results are in agreement that bitter kola leaf extract is a viable corrosion inhibitor of mild steel in H2SO4 solution. [ABSTRACT FROM AUTHOR]

There has been an urgent demand for novel neutron shielding materials (NSMs) with high mechanical strength and low acid corrosion rate to be used in compact shielding design. In this contribution, BPO4 ceramics (BPCs), one of the candidates for such materials, was successfully fabricated by a two-step method using H3BO3 and H3PO4 as raw materials. The evolution of the microstructures was then investigated, followed by testing of mechanical/thermal properties, acid corrosion resistance, and neutron shielding performance. The experimental results indicated that the calcination temperature as well as H3BO3 content in raw materials intuitively affected the densification process of the BPCs. The as-pared BPCs showed reliable mechanical properties with maximum CMOR, compressive strength and elastic modulus of 26.99 MPa, 86.89 MPa and 28.42 GPa, respectively, which also showed a high neutron shielding rate and low acid corrosion rate of 65.11% and 0.016%. The obtained results imply that the BPCs was a promising NSM for use in compact shielding design.

In order to study the weakening mechanism and mechanical behaviors of hard lamprophyre of Carboniferous Permian coal-bearing strata in China’s mining area, lamprophyre samples were subjected to static rock dissolution experiments with pH values of 0, 2, and 4. The acid corrosion mechanism of lamprophyre was revealed from the weight changes of samples, characteristics of solution ion concentration, and macro-mechanical properties. The experimental results show that reaction occurred between lamprophyre and acid solution. With the increasing concentration of H+, the reaction was more intense, the degree of acid etching was higher, and the weight loss was greater. The internal damage induced by acid etching results in the slow extension of the compaction stage of stress–strain curve of uniaxial compression, and the obvious deterioration of mechanical properties of the lamprophyre. The uniaxial compressive strength of the lamprophyre in the dry state is 132 MPa, which decreased to 39 MPa under the acid etching condition, showing significant mudding characteristics. Dolomite (CaMg(CO3)2 with 19.63%) and orthoclase (KAlSi3O8 with 31.4%) in lamprophyre are the major minerals constituents involved in acidification reaction. Photomicrograph recorded from SEM studies reveals that the dissolution effect was directly related to the concentration of H+ in the solution. The dissolution effect was from the surface to the inside. The small dissolution pores became larger and continuously expanded, then finally formed a skeleton structure dominated by quartz. The content of K+, Ca2+, and Mg2+ in the solution after acid etching reaction indicates that the acidified product of orthoclase is colloidal H2SiO3, which adhered to the surface of samples during acid etching and hinders the further acidification of minerals. The dissolution of dolomite and orthoclase under acidic conditions directly leads to the damage of their structure and further promotes the water–rock interaction, which is the fundamental reason for the weakening of the mechanical properties of lamprophyre.

Pomelo peel extract (PPE) was evaluated as green and renewable corrosion inhibitor for mild steel in 1.0 mol/L H3PO4 solution. The inhibition behaviour was studied using mass loss, potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) measurements. The chemical structure of PPE was investigated using Fourier transform infrared (FT-IR) and ultraviolet-visible (UV–vis) spectroscopy. The corrosion morphology of mild steel was analysed via scanning electron microscopy (SEM). The adsorption thermodynamics and kinetics was discussed. The results show that PPE confers an acceptable long-term effect (inhibition efficiency of 95.0% and 92.8% for corroding 23 h and 224 h in the presence of 5.0 g/L PPE inhibitor) and functions as a mixed inhibitor. The adsorption of PPE on mild steel simultaneously follows the Langmuir, El-Awady and Temkin isotherms at 35, 45 and 55 °C. PPE is mixed adsorption dominated with physical adsorption at room temperature or with higher PPE concentrations. PPE possesses many polar functional groups such as hydroxyl, carbonyl and hetero-aromatic rings. The inhibition mechanism is closely related to these polar groups, as is the surface coverage of steel.

We have synthesized a ternary glycine-functionalized graphene/Fe3O4 nanocomposite referred as Gr/Fe@Gly NC which was characterized by fourier transform infrared spectroscopy analysis (FT-IR), X-ray diffraction, high-resolution scanning electron microscopy/energy-dispersive X-ray spectroscopy (HR-SEM/EDS) and the transmission electron microscopy. The effectiveness of synthesized nanocomposite as anticorrosive material for mild steel in the acid medium was assessed using weight loss, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) complemented with FT-IR and SEM studies. The results of weight loss study depicted its effectiveness and stability up to 60 °C at very low concentrations. FT-IR and SEM studies supported the existence of a protective film on the inhibited steel surface. The adsorption followed the Langmuir adsorption isotherm; as such, it approximated and defined the thermodynamic and kinetic parameters governing the adsorption process. ANOVA statistical check confirmed that there is statistically no significant difference between the inhibition efficiencies obtained through weight loss, PDP and EIS techniques. [ABSTRACT FROM AUTHOR]

Benzyl isothiocyanate (BITC) was used as anticorrosive agent for the corrosion mitigation of stainless steel in 0.5 M hydrochloric acid medium. The corrosion inhibition study of (BITC) was investigated by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques in the temperature range of 303–323 K. The study was done to get optimum inhibition efficiency. The surface morphology was studied using scanning electron microscopy (SEM). Elemental mapping was done by energy dispersive X-ray (EDX) studies. Suitable mechanism was proposed for corrosion and inhibition process. Quantum chemical calculations were done and discussed in detail using density functional theory (DFT). Maximum inhibition efficiency of 86% was achieved for the addition of 0.025 g L−1 of the inhibitor at 308 K. BITC acted as mixed inhibitor and obeyed Langmuir adsorption. Surface morphology studies reaffirmed the adsorption of BITC onto the surface of steel. Quantum chemical calculations supported experimental observations. [ABSTRACT FROM AUTHOR]

A new eutectic high-entropy alloy (EHEA) of Cr 41 CoFeNi was prepared by arc melting technique. The microstructure and corrosion resistance of the Cr 41 CoFeNi EHEA were systematically investigated by EBSD, TEM, EIS and XPS analyses. The results revealed that the Cr 41 CoFeNi EHEA showed a dual-phase structure consisting of BCC phase and FCC phase, and the morphologies displayed the lamellar eutectic and network-shaped eutectic. Compared with 316 L stainless steel, the Cr 41 CoFeNi EHEA exhibited a better anti-corrosion property in 0.5 M H 2 SO 4 solution. This was mainly attributed to the formation of a dense and stable Cr-oxide layer on the surface of Cr 41 CoFeNi EHEA, which retarded further dissolution of the matrix. Moreover, bound water could adsorb metal ions to form a new protective film, which played an important role in improving the corrosion resistance of the Cr 41 CoFeNi EHEA. However, the elemental segregation and chemical potential difference between phases increased the defects in the passive film and accelerated its pitting corrosion of low potential phase. Moreover, the (Co, Fe, and Ni)-enriched FCC structured phase was preferentially eroded. • A novel eutectic high-entropy alloy of Cr 41 CoFeNi(EHEA) was designed and fabricated • The corrosion mechanisms of EHEA and 316 L stainless steel(316 L SS) were clarified • The passive film thickness of EHEA was about 5.3 times greater than that of 316 L SS • The main constituents of passive film on EHEA were Cr-oxide and bound water [ABSTRACT FROM AUTHOR]

Sodium dimethyl dithiocarbamate (SDD) is commonly applied to mitigate the release of heavy metals (HMs) into the environment from municipal solid waste incineration fly ash (IFA). Despite this common application, limited research has been conducted on the impact of environmental conditions on chelate destabilization during long-term landfilling. In this study, a batch leaching test was performed on chelated IFA buried for 10 years, revealing that the leaching concentrations of Pb and Cd exceeded landfill standards by 51.7% and 26.0%, respectively, indicating the chelate destabilization occurrence. To elucidate this phenomenon, various physicochemical experiments were conducted to unveil the underlying mechanisms emphasizing changes in HMs fractions (Pb, Cd, Cr, Ni, Zn, Cu) under acidic corrosion, and exploring the microscopic perspective of the chelate destabilization process. The key findings were summarized as follows: (I) The immobilization effect of SDD on Zn and Cd was not highly effective, with most of these metals being fixed on IFA through inorganic complexes. Theses HMs destabilization showed a negative correlation with the pH levels, indicating that higher acidity facilitated the release of HMs (59.0 mg/kg for Zn and 5.8 mg/kg for Cd). (II) After exposure to acid corrosion, the stable fraction of HMs decreased, because HM-SDD complexes decomposed into inorganic salts and carbon disulfide. This process further exacerbates the transporting effect of HMs on chelated IFA, thereby increasing the long-term leaching risk. (Ⅲ) A leaching equilibrium of HMs existed at the IFA surface, primarily influenced by the types and concentrations of anions in the leachate. This study contributes to a deeper understanding of the factors influencing the stability of chelated IFA and provides valuable insights into the long-term environmental implications of such materials in landfill settings. • Acid corrosion led to an increase in leaching risk through changes in heavy metals fractions. • Dissolved SDD had a transporting effect on heavy metals. • A leaching equilibrium of heavy metals was observed at the surface of fly ash. • Chelate destabilization mechanisms were discussed based on microscopic insights. [ABSTRACT FROM AUTHOR]

• The inhibition of S235JR steel in HCl by poly(2-ethyl-2-oxazoline)(PO) is studied. • Myristyltrimethylammonium bromide (MTAB) and KI effect on PO is examined. • PO average inhibition efficiency (η) is 80 % at 1000 mg/L. • The additives synergistically enhanced the performance of PO. • PO + MTAB + KI can offer ∼ 99 % inhibition and corrosion rate of 0.09 mm/y after 72 h. Organic compounds that exhibit little or no toxicity, have high solubility properties, and are affordable are highly sought after as metal corrosion inhibitors. The key to formulating an effective and economically viable corrosion inhibitor is the identification of compounds with strong synergistic effects. The synergistic inhibition of S235JR carbon steel in 1 M HCl by poly(2-ethyl-2-oxazoline) (PO), KI, and myristyl trimethylammonium bromide (MTAB) is studied. The durability of the PO + KI + MTAB blend is examined for up to 72 h. Results reveal an average inhibition efficiency (η) of 80 % for PO at 1000 mg/L. Adding 5 mg/L KI or MTAB to 1000 mg/L PO raised η to 97 % or 94 % from EIS measurements. PO(1000 mg/L) + KI(5 mg/L) + MTAB(5 mg/L) produced ∼ 99 % inhibition and kept the corrosion rate at 0.09 mm/y for up to 72 h. Spectroscopic and computational studies reveal PO interacted with the steel surface making use of the carbonyl functional group. The DFT calculations and MD simulations confirm the favorable tendency of the PO molecule to adsorb on the metal surface and the synergistic adsorption with KI and MTAB. Furthermore, SEM and AFM results confirm the high inhibitive performance of the blend. PO + KI + MTAB blend is highly recommended for long-term acid pickling of a metal surface and acid cleaning of plants. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effectiveness of Phenobarbitone (5-Ethyl-5-phenyl-1,3-diazinane-2,4,6-trione), for mitigating the deterioration of mild steel (MS) in 1 M HCl by using an expired drug. • Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) studies were performed to measure the -efficiency and to explain the adsorption isotherm. • To analyze thermodynamic and kinetic parameters at higher temperatures. • Surface morphology studies were conducted using scanning electron microscopy (SEM), electron-dispersive X-ray (EDAX), atomic force microscopy (AFM) techniques and contact angle measurements (CA). The research undertaken highlights the effectiveness of pharmaceutical drug Phenobarbitone (5-Ethyl-5-phenyl-1,3-diazinane-2,4,6-trione) (PB) as inhibitor to mitigate corrosion of mild steel (MS) in 1 M HCl. Corrosion studies were done by electrochemical techniques including potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) in the absence and presence of the Phenobarbitone (PB) drug. Kinetic parameters were calculated by studying the corrosion rate at different temperatures. Results were fitted into suitable adsorption isotherm and from the adsorption data thermodynamic parameters were computed and discussed in detail. Surface morphology studies were conducted using scanning electron microscopy (SEM), electron-dispersive X-ray (EDAX), and atomic force microscopy (AFM) techniques. The nature of the protective layer formed over the metal was studied by measuring the contact angle (CA), which demonstrated the formation of the adsorbed inhibitor layer. Inhibition efficiency increased with increase in concentration of inhibitor and with increase in temperature. For the addition of 0.04 gL-1, the maximum corrosion inhibition efficiency of 78.3 % was achieved at 313 K. Inhibitor acted as a mixed inhibitor with more control over the anodic reaction. Increase in efficiency with increase in temperature suggested the possibility of chemical adsorption. Inhibitor obeyed Langmuir adsorption isotherm, supporting chemical adsorption. Surface morphology clearly demonstrated the formation of barrier film on the surface of metal which prevented further dissolution of metal thereby decreasing the corrosion rate. [ABSTRACT FROM AUTHOR]

This study investigated synergistic effect of temperature, solution velocity, and sulphuric acid concentration on corrosion behaviour of carbon steel using response surface methodology. Electrochemical and surface characterisation techniques were employed. A statistically significant mathematical model was obtained, correlating corrosion rate to the environmental parameters. Temperature affected anodic reactions, while solution velocity influenced cathodic reactions. Acid concentration profoundly influenced corrosion mechanisms by altering deposition, dissolution, and properties of FeSO 4 surface layer. The lowest corrosion rate was 0.546 mm/year at 35 ° C , 98.5 wt%, 0 rpm, and the highest was 368.223 mm/year under 70 ° C , 49 wt% and 500 rpm. • Corrosion behaviour of carbon steel using response surface methodology was studied. • Synergistic effect of temperature, solution velocity, and acid concentration was investigated. • A statistically significant mathematical model for corrosion rate was obtained. • Temperature affected anodic reactions, while solution velocity influenced cathodic reactions. • Acid concentration influenced corrosion mechanisms by altering FeSO 4 surface layer. [ABSTRACT FROM AUTHOR]

In the realm of oil and natural gas, material durability is compromised by sand particle abrasion, corrosive media, and hydrogen-induced cracking. This study investigates the impact of PTFE on wear and corrosion resistance of Ni-P coatings in a CO 2 environment. Hydrogen barrier properties of the substrate, Ni-P, and PTFE are evaluated using the Devanathan-Stachursky cell. Results show that incorporating PTFE enhances the coating's wear and corrosion resistance, and hydrogen barrier performance compared to substrate and Ni-P alone. The coating effectively hinders corrosive media transmission. A comprehensive analysis of the Ni-P-PTFE corrosion mechanism is provided, along with a robust corrosion model. • Examined the influence of varied PTFE levels on morphology and wear traits of chemically deposited Ni-P coatings. PTFE's innate hydrophobicity reduces grain size. A minor PTFE addition enhances hardness via dispersion strengthening. Simultaneously, PTFE's self-lubrication reduces direct material-wear debris contact, bolstering wear resistance. • Examined PTFE's hydrogen barrier in the petroleum sector. PTFE notably fortified hydrogen resistance, curbing coating's hydrogen-induced cracking susceptibility. This, ascribed to enhanced coating integrity, curtails hydrogen ingress, thus minimizing cracking. • Conducted an extensive study on Ni-P-PTFE coating's corrosion resistance in CO2-saturation. PTFE improved surface integrity, functioning as a corrosion inhibitor via stable C-F bonds. The "maze effect" by PTFE and Ni-P thwarted corrosive media. • An in-depth analysis of the corrosion mechanism of Ni-P-PTFE in a saturated CO2 environment yielded a robust corrosion model, offering a thorough elucidation of the excellent CO2 saturation corrosion resistance of Ni-P-PTFE coatings. [ABSTRACT FROM AUTHOR]

Preventing the corrosion of iron in inaccessible structures requires a coating method that reaches all surface areas and creates a uniform protective layer. An ages old practice to protect iron artefacts is to coat them with animal fat, that is, a mixture of lipids. This “method” is accidentally ingenious: some natural phospholipids found in animal fat have the potential to form a tightly packed self-assembled monolayer on metal oxide surfaces, similar to the surfactant monolayers that have attracted increasing attention lately. Thus, the most primitive corrosion prevention method may point at a way to coat complex iron structures in an industrial environment. Here the ability of phosphatidic acid, a natural lipid, to coat and protect iron surfaces was examined. Iron coated quartz crystal microbalance (QCM) sensors were used for the experiments, to monitor the deposition of the lipid as well as the acidic corrosion (dissolution) of iron in situ, in real time. The sensors were coated by self-assembled monolayers of di-myristoyl phosphatidic acid using the liposome deposition method. In this process, 50-100 nm vesicles formed by the lipid are delivered in an aqueous solution and spontaneously coat the iron surfaces upon contact. QCM and ellipsometry measurements confirmed that continuous bilayer and monolayer surface coatings can be achieved by this method. QCM measurements also confirmed that the layers were corrosion resistant in 0.01M acetic acid solution that would dissolve the thin iron layer in minutes in the absence of the protective coating. XPS results suggested a chemisorption-based mechanism of phosphatidic acid attachment to the iron surface. Hence, liposome deposition of phosphatidic acid offers a suitable solution to coat iron surfaces in inaccessible structures in situ.

New Mannich bases, 3-morpholino-1-phenylpropan-1-one (MPO) and 3-morpholino-1-phenyl-3-(pyridin-4-yl) propan-1-one (MPPO), were synthesized, characterized, and studied as corrosion inhibitors for N80 steel in 1 M hydrochloric acid (HCl) solution using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and FT-IR spectroscopy. The inhibition efficiency increases with increasing inhibitor concentrations, and the corrosion inhibition efficiency of the MPO and MPPO could reach 90.3% and 91.4%, respectively, at a concentration of 300 ppm at 305 K. The effect of the temperature on the corrosion inhibition behavior of inhibitors was discussed. Electrochemical tests showed that the synthesized inhibitors are mixed. The EIS test results showed that the presence of MPO and MPPO reduced the double-layer capacitance in the corrosion process, thereby reducing the charge transfer resistance. The SEM and EDX results showed that the MPO and MPPO formed a uniform adsorption film on the surface of the N80 steel. The adsorption mechanism of the inhibitors was simulated with different adsorption models and the results showed that the inhibitors were the chemisorbed type. The results of the FT-IR spectroscopy proved that the inhibitor interacted with metal atoms on the steel surface.

In the present work, SnO2 was successfully coated on mild steel (MS) by the sol–gel method at different times (15,30,45 min). These coatings were developed to improve the performance of corrosion protection of MS in a 0.5 M HCl solution. The morphological and structural characterization of obtained electrodes was investigated with the help of characterized by Field-emission scanning electron microscopy (FE-SEM) and the contact angle. The corrosion behavior of uncoated and at 15,30,45 min SnO2-coated MS electrodes were investigated by open circuit potential (OCP)–time, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques in 0.5 M HCl solution at 20–50 °C. Moreover, the potential of zero charges (pzc) of MS was determined using the EIS technique. EIS results indicated that the maximum inhibition efficiency (85%) during the coating time of 30 min at 30 °C. As a result, the SnO2 film effectively protected on the MS against corrosion and reduced its corrosion rate in the HCl solution. The SnO2 was coated on MS electrode at 15, 30, 45 minutes by a simple sol-gel method. The surface morphologies were characterized by FE-SEM and the contact angle. The corrosion behaviors of samples were investigated by electrochemical techniques. The SnO2 provides good corrosion protection against the attack of corrosive media. [ABSTRACT FROM AUTHOR]

Interaction of metal surfaces with organic molecules has a significant role in corrosion inhibition of metals and alloys. More clarification, from both experimental and computa­tional view is needed in describing the application of inhibitors for protection of metal surfaces. In this study, the surface adsorption and corrosion inhibition behavior of metol­azone, a quinazoline derivative, on mild steel in 0.02, 0.04, 0.06, and 0.08 M HCl solutions were investigated. Weight loss, potentiodynamic polarization and electrochemical impe­dance spectroscopy techniques were used. The optimum inhibition efficiencies of 75, 82 and 83 % were found by these three techniques at the optimum inhibitor concentration of 500 mg/L and 303 K. Scanning electron microscopy (SEM) was used to confirm adsorption of quinazoline derivative on the surface of the mild steel. Computational simulations were additionally used to give insights into the interaction between quinazoline inhibitor and mild steel surface. Thermodynamic parameters of mild steel corrosion showed that quinazoline derivative functions as an effective anti-corrosive agent that slows down corrosion process. Potentiodynamic polarization results revealed a mixed-type inhibitor, while the result of the adsorption study suggests that adsorption of the inhibitor on the mild steel surface obeys the physical adsorption mechanism and follows Langmuir adsorption isotherm model.

The efficiency of corrosion inhibition for waterborne polyurethane based on N-tert-butyl diethanolamine (tB-WPU) is investigated using different techniques. Corrosion weight loss, open circuit potential experiments, electrochemical impedance spectroscopy, and potentiodynamic polarization measurements show that both a commercial reagent and a polyurethane-based inhibitor prevent corrosion at increasing temperature to 50 °C. At 75 °C, the activity of both reagents is reduced. In stirring conditions, the effectiveness of acid corrosion inhibition (25 °C, 500 ppm) drops abruptly from 89.5% to 60.7%, which is related presumably to the complexity of binding the polymer molecules to the metal surface. As follows from thermodynamic calculations, the adsorption of tB-WPU on the metal surface in 2M HCl can be treated as a physisorption. Model quantum–chemical calculations support the experimental studies and elucidate the nature of steel surface–inhibitor molecule chemical bond, which is realized mainly by carboxyl and amino groups. It is concluded that WPUs can be considered as a perspective alternative to commercial oilfield reagents due to their versatility.

The scrutiny of the impeding properties of vigna radiata (VR) on mild steel corrosion in sour environs (1 M HCl and 0.5 M H2SO4) was done by means of gravimetric, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods (PDP). Polarization findings revealed that VR retarded the corrosion process in a mixed‐mode manner. Adsorption of the active components of VR was found to be in line with Langmuir adsorption isotherm. The obtained PDP result was complemented by the EIS findings. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and the theoretical technique was used to complement the results. [ABSTRACT FROM AUTHOR]

The method of electrochemical impedance spectroscopy was used to study the adsorption of an IFKhAN-92 inhibitor, 3-substituted 1,2,4-triazole, on low-carbon steel from 2.0 M H2SO4 (22°C). It was shown that the Temkin isotherm with a relatively high value of free energy of adsorption (−ΔGads) = 49 kJ/mol described its adsorption. It was suggested that the inhibitor adsorption has a chemisorption nature, which is testified both by the description of the kinetics of adsorption by the Roginsky–Zeldovich equation and a high protective aftereffect of the inhibitor adsorbed on the steel surface. [ABSTRACT FROM AUTHOR]

It is shown that the multimolecular protective layer of an organic inhibitor formed on the surface of chromium–nickel steel in an HCl solution containing a triazole derivative, the inhibitor IFKhAN-92, has a protective aftereffect in background solutions of the same acid. Such a protective layer is chemically bonded to the Fe, Cr, and Ni oxide and hydroxide phase adjacent to the metal phase. The lower part of the polymolecular protective layer of the organic inhibitor consists of a polymer complex formed by IFKhAN-92 molecules, metal cations (Fe, Cr, and Ni), and chloride anions, and the outer part consists of physically adsorbed IFKhAN-92 molecules, which are easily removed from the metal surface during ultrasonic washing of samples. [ABSTRACT FROM AUTHOR]

The performance of 1‐vinyl‐3‐allyl imidazolium bromide ([VAIM][Br]) for inhibiting the corrosion of carbon steel in 1 M HCl solution from 298 K to 338 K was assessed. Electrochemical impedance spectroscopy (EIS) measurements proved that the inhibition efficiency (η) of [VAIM][Br] was as high as 95 %, and after immersion of 144 h, η still kept more than 90 %. Polarization curve verified that [VAIM][Br] acted as a mixed‐type inhibitor and adsorption of [VAIM][Br] was found to obey Langmuir adsorption isotherm. Molecular dynamic simulations suggested that the addition of vinyl group increased interaction energy between [VAIM]+ and (0 0 1) plane of Fe from 43.92 kcal mol−1 to 71.98 kcal mol−1. Liquid chromatography‐mass spectrometry (LC‐MS) and UV‐vis spectrum demonstrated that [VAIM][Br] and Fe atom can form stable complex (Fe2(VAIM)2Br4), which hindered the corrosion of carbon steel. [ABSTRACT FROM AUTHOR]

The inhibition performance of ionic liquids, abbreviated as [(CH 2)COOHMIm][HSO 4 , [(CH 2) 2 COOHMIm][HSO 4 , and [(CH 2) 3 SO 3 HMIm][HSO 4 was investigated for carbon steel in 0.5 M HCl solution. Results indicated that these ionic liquids could act as effective inhibitors by adsorption onto the steel surface, and the inhibition efficiency increases with cation alkyl chain length and concentration up to a limit. The inhibition efficiency of a sulfonate-type ionic liquid with a longer alkyl chain is higher than those of the carboxylate-type ionic liquids. Besides, the order of inhibition efficiency was verified by both computational calculation and electrochemical experimental observations. [ABSTRACT FROM AUTHOR]