Corrosion inhibition of carbon steel in hydrochloric acid by furan derivatives

The efficiency of three furan derivatives (2-methylfuran, furfuryl alcohol and furfurylamine), as corrosion inhibitors for carbon steel in 1 M HCl, has been determined by gravimetric and electrochemical measurements. These compounds inhibit corrosion even at very low concentrations, and furfuryl alcohol is the best inhibitor. Polarization curves indicate that all compounds are mixed inhibitors, affecting both cathodic and anodic corrosion currents. Adsorption of furan derivatives on the carbon steel surface is in agreement with the Langmuir adsorption isotherm model, and the calculated Gibbs free energy values confirm the chemical nature of the adsorption. The structural and electronic properties of these inhibitors, obtained using AM1, PM3, MNDO and MINDO/3 semi-empirical self-consistence field methods, are correlated with their experimental efficiencies.     

12-Aminododecanoic acid as a corrosion inhibitor for carbon steel

The inhibiting effect of 12-aminododecanoic acid (AA) on corrosion of carbon steel (CS) was investigated in hydrochloric acid of different pH, temperatures and over a prolonged period of time, and also in some other selected corrosive solutions. It was found that AA inhibits both partial corrosion reactions, with a slightly stronger inhibition of the anodic corrosion reaction. The corrosion protection mechanism is by formation of a surface-adsorbed AA monolayer that offers a hydrophobic barrier to transport of solvated corrosive ions to the surface. A maximum inhibition efficiency of 98.8 ± 0.5% was achieved in 0.5 M HCl. The adsorption of AA onto the CS surface was described by the Langmuir adsorption isotherm. The corresponding standard Gibbs energy of adsorption was calculated to be −26 kJ mol⁻¹. Polarization modulation infrared reflection absorption spectroscopy measurements revealed that the adsorbed AA monolayer is amorphous, which is due to the high heterogeneity of the CS surface.     

Synthesis,Surface Properties,and Inhibiting Action of Novel Nonionic Surfactants on Carbon Steel Corrosion in 1 M Hydrochloric Acid Solution

In the present study novel nonionic surfactants were synthesized, characterized, and tested as corrosion inhibitors for carbon steel in 1 M HCl solution. The inhibiting performances of these surfactants were studied by weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). The adsorption of these inhibitors was well described by Langmuir adsorption isotherm, and the kinetic parameters were calculated and discussed. The inhibition efficiency (IE) was found to rise with increasing the concentration of these inhibitors. Polarization measurements revealed that the inhibitors acted as mixed-type inhibitors. The efficiencies obtained from the impedance measurements were in good agreement with those obtained from the weight loss and potentiodynamic polarization techniques which prove the validity of these tools in the measurements of the tested inhibitors. The surface parameters of the synthesized nonionic surfactants were investigated and the results showed that these surfactants have lower values of surface tension and are effective as wetting and emulsifying agents.     

Temperature dependence of the electrochemical corrosion characteristics of carbon steel in a salty soil

The electrochemical corrosion characteristics of carbon steel in a salty soil at different temperatures were studied by measurements and analyses of potentiodynamic polarization curves, linear polarization resistance and electrochemical impedance spectroscopy. The results showed that the mass-transfer of dissolved oxygen plays an essential role in carbon steel corrosion, and the whole corrosion process is mix-controlled by both activation and mass-transfer steps. Passivity can be developed on carbon steel in the soil at low temperatures. With the increase of temperature, the passive current density increases and the passive potential range decreases. When temperature is elevated to a certain value, 50 °C in this system, passivity cannot be maintained and the steel is dominated by an active dissolution status. Anodic Tafel slope decreases continuously with the increase in temperature, which is mainly due to the enhanced electrode reaction rate at an elevated temperature. Simultaneously, cathodic Tafel slope increases with temperature continuously due to the decrease of the solubility of dissolved oxygen in soil. Since the diffusion activation energy is generally much smaller than the reaction activation energy, the effect of temperature on diffusion is far less than that on electrode reaction rate.     

Electrochemical behaviour of passive films on molybdenum-containing austenitic stainless steels in aqueous solutions

Passivation and its breakdown reactions have been studied on Mo-containing stainless steel specimens using different electrochemical techniques. Mo-containing stainless steel specimens were polarized in both naturally aerated NaCl and Na₂SO₄ solutions of different concentrations at 25 ± 0.2 °C between −1000 and 1500 mV versus saturated calomel electrode (SCE). The results of potentiodynamic polarization showed that i_corr and i_c increases with increasing either Cl⁻ or SO₄²⁻ concentration indicating the decrease in passivity of the formed film. EIS measurements under open circuit conditions confirmed that the passivity of the film decrease with increase in either Cl⁻ or SO₄²⁻ concentration.     

Study of the variational patterns for corrosion kinetics of carbon steel as a function of dissolved oxygen and NaCl concentration

The simultaneous occurrences of electrochemical reactions responsible for corrosion of carbon steel in NaCl solutions have been analyzed on the basis of the mixed potential theory in order to determine the combined effect of dissolved oxygen and NaCl concentration on corrosion potential, corrosion current density and hydrogen evolution. This was achieved through the estimation of the functional dependence from both, the dissolved oxygen and the NaCl concentration for each of the kinetic parameters involved in the corrosion process. The main finding is the existence of the critical dissolved oxygen value at which a notorious change in variational pattern for corrosion potential, corrosion current density and hydrogen evolution is observed. The validity of this feature is supported from experimental evidence reported in previous investigations. In this context the role of pitting corrosion, oxide film and diffusional effects are discussed.     

Synthesis and Inhibition Effect of a Novel Tri-cationic Surfactant on Carbon Steel Corrosion in 0.5 M H2SO4 Solution

A novel Tri-cationic surfactant was synthesized, purified and characterized. The critical micelle concentration value of the prepared surfactant was determined by surface tension and conductivity measurements. The surface parameters were calculated by surface tension measurements. The relationship between the surface properties and the corrosion inhibition efficiency of the prepared surfactant was discussed. The inhibition effect of the novel Tri-cationic surfactant on carbon steel corrosion in 0.5 M H₂SO₄ was studied by potentiodynamic polarization, electrochemical impedance spectroscopy and weight loss techniques. Potentiodynamic polarization studies revealed that the inhibitor acted as a mixed-type inhibitor. The high inhibition efficiency was attributed to the blocking of active sites on the steel surface through the adsorption of inhibitor molecules. Inhibitor adsorption on the carbon steel surface was in accordance with the Langmuir adsorption isotherm model. Thermodynamic adsorption and kinetic parameters were obtained from weight losses at different temperatures (20–60 °C).     

缓蚀稳定剂SM2001性能研究

研究了复合型缓蚀剂SM2001对45＃碳钢在模拟工艺水中的缓蚀性能，原子吸收法测定冷却水中溶出Fe^2 量及极化曲线测试结果表明，SM2001对45＃碳钢具有良好的腐蚀性能，在金属表面形成性能良好的缓蚀膜。     

Effects of γ-radiation versus H2O2 on carbon steel corrosion

The effect of ionizing radiation on steel corrosion is an important materials issue in nuclear reactors. In the presence of ionizing radiation water decomposes into both oxidizing and reducing species (e.g., OH, H₂O₂, O₂⁻) whose net interactions with steels are not fully understood. The effect of radiation on the corrosion kinetics of carbon steel has been studied at pH 10.6 and room temperature, using electrochemical and chemical speciation analyses. The present study investigates the effect of γ-radiation on carbon steel corrosion and compares it with that of chemically added H₂O₂, which is considered to be the key radiolytically produced oxidant at room temperature. Various oxide films were pre-grown potentiostatically on carbon steel electrodes, and then exposed to either γ-radiation at a dose rate of ∼6.8 kGy h⁻¹ or to H₂O₂ in a concentration range of 10⁻⁶ to 10⁻² M. The corrosion kinetics were studied by monitoring the corrosion potential (E_CORR), and periodically performing linear polarization (LP) and electrochemical impedance spectroscopy (EIS) measurements.     

Electrochemical behavior of organic and inorganic complexes of Zn(II) as corrosion inhibitors for mild steel: Solution phase study

This work intends to study inhibitive performance of organic and inorganic complexes of Zn(II) using electrochemical techniques along with surface analysis. In this regard, inorganic zinc aluminum polyphosphate pigment as modified zinc phosphate and zinc acetylacetonate and benzimidazole mixture representing organic replacement of zinc phosphate were employed. Through taking advantage of electrochemical impedance spectroscopy and DC polarization, two mentioned approaches were indicated to be efficient. Charge transfer resistance and corrosion current density values exhibited superiority of zinc aluminum polyphosphate and mixture of zinc acetylacetonate and benzimidazole compared to zinc phosphate and also zinc acetylacetonate and benzimidazole as individual inhibitors. Corrosion inhibition efficiencies calculated based on charge transfer resistance in consistent with those calculated from corrosion current density showed the following sequence; zinc aluminum polyphosphate > mixture of zinc acetylacetonate and benzimidazole > zinc acetylacetonate > zinc phosphate > benzimidazole. Showing film formation, surface analysis SEM/EDX confirmed the results obtained by electrochemical methods.     

Inhibiting properties and adsorption of some thioamides on mild steel in sulphuric acid solutions

The inhibiting properties and adsorption behaviour of thioacetamide (TAA), thiobenzamide (TBA) and thiocinnamamide (TCA) on mild steel in sulphuric acid solution were studied by gravimetric, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. TBA and TCA were found to be mixed type inhibitors providing good corrosion inhibition. Different mechanisms of adsorption and corrosion inhibition were observed for the tested thioamides. In the cases of TBA and TCA, the adsorption of the compounds is chemical and the values of the activation energy (Ea) and the pre-exponential factor (A) are lower than the corresponding values observed in inhibitor free solution. The adsorption of TAA is physical and the values of Ea and А are higher than the corresponding values in sulphuric acid solution. The adsorption process of TBA and TCA on the mild steel/sulphuric acid solution interface is described by Langmuir’s isotherm. A correlation between the adsorption capability and the inhibiting efficiency of the molecules and their donor–acceptor properties (E _HOMO and E _LUMO) has been established. It is ascertained that the protection effect of TAA depends on the amount of hydrolysis products.     

Soluble conducting poly(aniline-co-orthotoluidine) copolymer as corrosion inhibitor for carbon steel in 3% NaCl solution

The copolymer poly (aniline-co-o-toluidine) noted poly(ANI-co-OT) is chemically synthesized, and characterized by FT-IR, UV-Vis, TGA and XRD techniques. The results show that this copolymer presents new structures and it is more thermally stable than the corresponding parent homopolymers. It is found that it is soluble in dimethylformamide (DMF), while the homopolymers have a low solubility. Techniques such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) have been employed to study the inhibition effects of this copolymer on the corrosion of carbon steel in 3% NaCl solution. The results show an increase in inhibition efficiency as a function of copolymer concentration to attain an optimum (70%) for a concentration close to 100 ppm. This is due to the higher coverage of the carbon steel electrode surface as shown by the Temkin adsorption isotherm. The Potentiodynamic polarisation studies reveal that this copolymer acts as a mixed-type inhibitor. The results obtained by potentiodynamic and EIS techniques are in good agreement.     

[BMIM]BF4 ionic liquids as effective inhibitor for carbon steel in alkaline chloride solution

The inhibition action of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF₄) ionic liquids towards carbon steel corrosion in alkaline chloride solution was investigated by electrochemical measurements. The morphology of the surface was examined by atomic force microscopy (AFM), and the surface composition was evaluated via X-ray photoelectron spectroscopy (XPS) as well in order to verify the presence of inhibitor on the carbon steel surface. The results showed that the compound effectively suppressed both cathodic and anodic processes of carbon steel corrosion in alkaline solution by multi-center adsorption on carbon steel surface according to Langmuir adsorption isotherm, and acted as a mixed type inhibitor. The inhibition mechanism was proposed based on the viewpoint of complex physic-chemical interactions between the cationic inhibitor molecule and the carbon steel surface.     

Evaluation of some bipyridinium dihalides as inhibitors for low carbon steel corrosion in sulfuric acid solution

Inhibition of low carbon steel (LCS) corrosion in 0.5 M H₂SO₄ solution by three bipyridinium dihalides (TMbPyBr₂, HMbPyBr₂ and MPhbPyCl₂) was evaluated by potentiodynamic polarization curves, EIS and SEM techniques. The effectiveness of the inhibitors is ranked as follows: MPhbPyCl₂ ≅ TMbPyBr₂ > HMbPyBr₂. The compounds behave as mixed-type inhibitors and their adsorption on the steel surface obeys the Langmuir adsorption isotherm. EIS measurements indicate that charge transfer controls the corrosion of steel in the absence and presence of the inhibitors and the equivalent circuit R_e(R_ctQ_dl) represents the electrode/solution interface either at the corrosion potential or at −75 and 30 mV versus E_corr. The compounds show maximum inhibition efficiency at 35 °C. The mechanism of corrosion inhibition was discussed in the light of the molecular structure of the bipyridinium salts.     

Investigation of the corrosion protection of SiOx-like oxide films deposited by plasma-enhanced chemical vapor deposition onto carbon steel

The paper reports on the corrosion behavior of carbon steel coated with thin SiO_x-like oxide films. The SiO_x-like coatings were deposited by plasma-enhanced chemical vapor deposition (PECVD) and their thickness was varied between 20 and 200 nm. The coated carbon steel interfaces were investigated for their corrosion protection efficiency when immersed in an aqueous saline solution of 3% NaCl. FTIR measurements and electrochemical impedance spectroscopy (EIS) experiments revealed that thin SiO_x-like coating layers (20 nm thick) do not prevent the carbon steel from corrosion, while thicker silica layers (d ≥ 100 nm) protect efficiently carbon steel interfaces in highly saline media with a protection efficiency of about 96% for a 200 nm thick coating.     

Corrosion inhibition of mild steel in acidic medium using hydrazide derivatives

The corrosion inhibition characteristics of N′-[(1E)-(4-hydroxy phenyl) methylene] isonicotinohydrazide (HIH) & N′-[(1E)-(4-hydroxyl-3-methoxy phenyl) methylene] isonicotinohydrazide (HMIH) on mild steel corrosion in 1 M hydrochloric acid were investigated by weight loss, potentiodynamic polarization and impedance techniques. The inhibition efficiency increased with increase in inhibitor concentration but decreased with increase in temperature. The thermodynamic functions of dissolution and adsorption processes were evaluated. The polarization measurements indicated that the inhibitors are of mixed type. The adsorption of the compounds was found to obey Langmuir’s adsorption isotherm. Passive film characterization was done by Fourier transform infrared (FTIR) spectra and scanning electron microscopy (SEM).     

Electrochemical frequency modulation as a new technique for monitoring corrosion inhibition of iron in acid media by new thiourea derivative

The electrochemical frequency modulation EFM technique provides a new tool for electrochemical corrosion monitoring. EFM is a non-destructive technique as electrochemical impedance spectroscopy (EIS). EFM technique was used in comparison with the traditional dc and ac techniques. Results obtained by EFM technique were shown to be in agreement with other electrochemical techniques. With EFM technique, a corrosion rate can be obtained instantaneously in very short time which makes this technique ideal in online corrosion monitoring. New synthesized thiourea derivative named 1,3-diarylidenethiourea (DAT) was examined as a new corrosion inhibitor for iron in 1 M hydrochloric acid solution.     

Electrochemical investigations of naphthenic acid corrosion for carbon steel and the inhibitive effect by some ethoxylated fatty acids

The electrochemical behavior and corrosion of carbon steel in various types of naphthenic acid solutions have been studied by using cyclic voltammetry technique. The data reveal that the anodic excursion spans of carbon steel in naphthenic acid solution are characterized by the occurrence of a well-defined anodic peak (peak A), followed by a passive region. The passivation may be related to the formation and precipitation of oxide film on the electrode surface. The data reveal that increasing naphthenic acid concentration enhances the anodic peak current density (I_PA) and shifts its peak potential towards more positive values. The corrosion rate of carbon steel depended critically on the naphthenic acid types. The rate of the corrosion process increased with increasing in molar mass of naphthenic acid, reaching a maximum value in the presence of CHPA acid (C₉), and then decreased.

Potentiodynamic polarization measurements indicated that ethoxylated fatty acid derivatives have a strong effect on the corrosion behavior of the carbon steel in naphthenic acid solutions. The inhibition efficiency of these compounds was found to vary with their nature and concentration. The order of effectiveness of the inhibitors was OL(EO)₈₀ > OL(EO)₄₀ > OL(EO)_20. The adsorption of ethoxylated fatty acid on the carbon steel surface in naphthenic acid solutions was found to obey Frumkin isotherm and kinetic-thermodynamic model.     

Corrosion inhibition of mild steel in 1.0 M hydrochloric acid medium by new photo-cross-linkable polymers

Photo-cross-linkable polymers namely, poly((E)-(1-(5-(4-(3-(4-chlorophenyl)-3-oxoprop-1-enyl)phenoxy)pentyl)-1H-1,2,3-triazol-4-yl)methyl acrylate) (Cl-5) and poly((E)-(1-(5-(4-(3-(4-chlorophenyl)-3-oxoprop-1-enyl)phenoxy)decyl)-1H-1,2,3-triazol-4-yl)methyl acrylate) (Cl-10) were synthesized by click-chemistry. The polymers were characterized by using various spectroscopic techniques and the rate of cross-linking was evaluated by absorption spectroscopy. The inhibitory action of the photo-cross-linkable polymers was evaluated for mild steel (MS) corrosion in 1.0 M hydrochloric acid solution (HCl) by means of electrochemical impedance spectroscopy, potentiodynamic polarization measurements, adsorption isotherms and surface analysis. To the best of our knowledge, these are the most efficient inhibitors (Cl-5 and C-10) for the corrosion of MS in HCl reported so far. Tafel polarization measurements showed that the polymers act as mixed type inhibitors and the adsorption of the inhibitors onto the MS surface followed the Langmuir adsorption isotherm. The values of the Gibbs free energy of adsorption (ΔG_ads) strongly supported spontaneous physicochemical adsorption of inhibitor molecules on the MS surface. The SEM-EDX results confirmed that the cross-linked polymers inhibited the corrosion to a greater extent than the intact polymer.