Water soluble conducting polymer composite of polyvinyl alcohol and leucine: An effective acid corrosion inhibitor for mild steel

A new corrosion inhibitor namely poly(vinyl alcohol‐leucine) composite (PVAL) has been synthesized and its influence on corrosion inhibition of mild steel in 1 M hydrochloric acid solution has been studied by weight loss and potentiodynamic polarization techniques. The composite (PVAL) showed more than 95% inhibition efficiency (IE) at an optimum concentration of 0.6% by weight. The inhibition efficiency of inhibitor has been found to vary with inhibitor concentration, solution temperature, and immersion time. Various kinetic and thermodynamic parameters (E_a, ΔH_o, ΔS_o for corrosion and ΔG_ads, ΔH_ads, ΔS_ads for adsorption) reveal a strong interaction between inhibitor and mild steel surface. The negative values of ΔG_ads indicate the spontaneous adsorption of the inhibitor on mild steel surface. Potentiodynamic polarization studies showed PVAL as mixed type inhibitor. It inhibits mild steel corrosion by blocking the active sites of the metal. Electrochemical impedance spectroscopic (EIS) techniques were also used to investigate the mechanism of corrosion inhibition.     

向日葵盘提取物在0.5mol/L H2SO4溶液中对碳钢的缓蚀作用

以超声辅助法提取得到的向日葵盘提取物(HALE)为缓蚀剂,采用腐蚀浸泡试验、电化学试验研究HALE在0.5mol/L H2SO4溶液中对碳钢的缓蚀作用。结果表明:HALE对碳钢缓蚀效果良好,缓蚀率随HALE加量增加而增大,但随温度升高而降低;HALE在碳钢表面的吸附符合Langmuir吸附模型,是以物理吸附为主的混合吸附;电化学测试结果表明HALE是偏阳极混合抑制型缓蚀剂。     

Inhibition of 304 stainless steel corrosion in acidic solution by Ferula gumosa (galbanum) extract

The inhibition effect of the extract of galbanum (Ferula gummosa Boiss.) on the corrosion of 304 stainless steel in 2 M HCl solution was studied by weight loss measurements, Tafel polarization, and electrochemical impedance spectroscopy (EIS) methods. It was found that the inhibition efficiency (IE) increases as the extract concentration is increased. Tafel polarization method revealed the mixed mode inhibition of galbanum extract (GE) with predominant control of anodic reaction. The effect of temperature on the corrosion behavior of steel indicates that inhibition efficiency of the natural substance increases with the rise in temperature. At all temperatures, the adsorption of the extract components onto the steel surface was found to follow the Temkin adsorption isotherm.     

Effect of Co and W on the corrosion behaviour of 1% Cr steel in flowing synthetic seawater

The aqueous corrosion characteristics of 1% Cr‐steel alloyed with small amounts of Co and W in synthetic seawater was studied by using immersion weight‐loss tests, electrochemical corrosion tests (potentiodynamic tests and electrochemical impedance spectroscopy (EIS) measurements) and analytical techniques. 1% Cr steels containing Co or W from 0.2 to 0.4 wt.% showed higher corrosion resistance than the 1% Cr steel in the immersion and potentiodynamic tests. EIS measurements showed that the Nyquist plot presented one time constant. Furthermore, the Co‐ and W‐bearing steels present higher R_p values than the 1% Cr steel through all the test period. The better corrosion resistance of the Co‐and W‐bearing steels is attributed to the protectiveness of the surface layer. The corrosion products were examined using electron probe microanalysis (EPMA) and X‐ray photoelectron spectroscopy (XPS). The results of EPMA indicated that Cr was concentrated in the inner region of the rust layer, while Co and W were distributed all over the rust layer. XPS results showed that Co existed as a trivalent oxide in the rust layer and W in the rust appeared in the form of a WO₄ compound. These compounds act as a factor for corrosion resistance in aqueous solutions.     

一种二酰胺基吡啶季铵盐的合成及其缓蚀性能

利用2,3-吡啶二甲酸为主体和十二烷基胺进行酰化反应,合成了具有多个活性吸附中心的2,3-N-十二烷基-二甲酰胺吡啶衍生物,再进行季胺化反应增加其水溶性,开发出一种二酰胺基吡啶季铵盐缓蚀剂。利用动态高温高压浸泡试验和电化学试验在含二氧化碳模拟油田水中评价了该缓蚀剂对L245NCS钢的缓蚀性能。结果表明:该缓蚀剂是混合型缓蚀剂,在加量为50mg/L时,缓蚀率达到95%以上,同时对点蚀具有良好的抑制效果。     

几种植物叶提取物在HCl中对锌的缓蚀作用

采用失重法首次研究了钓鱼慈竹(Neosinocalamus affinis)竹叶提取物(NALE),三角枫(Acer buergerianum)叶提取物(ABLE)和滇润楠(Machilus yunnanensis)叶提取物(MYLE)在盐酸中对锌的缓蚀作用。详细考察了缓蚀剂浓度(0.1~1.0g/L)、温度(30~60℃)、腐蚀浸泡时间(6~72 h)和盐酸浓度(0.01~0.05 mol/L)对缓蚀性能的影响。结果表明:三种植物提取物在0.01 mol/L HCl溶液中均对锌具有良好的缓蚀作用,且在锌表面的吸附符合Langmuir吸附等温式。缓蚀率随缓蚀剂浓度的增加而增大,但随温度、盐酸浓度和腐蚀浸泡时间的增加而减小。三种植物提取物的缓蚀率排序为:NALEABLEMYLE。     

Adsorption effect of 1‐((2‐hydroxynaphtalen‐1‐yl) (phenyl)methyl)urea on the carbon steel corrosion in hydrochloric acid media

The adsorption effect of 1‐((2‐hydroxynaphtalen‐1‐yl)(phenyl)methyl)urea (HNPU) on corrosion behavior of carbon steel in 1 M hydrochloric acid solution was investigated using weight loss, potentiostatic polarization, and infrared spectroscopy methods. Surface morphology was studied by scanning electron microscopy (SEM). The experimental results, suggest that HNPU inhibited the corrosion of carbon steel in acid solution and the inhibition efficiencies increased as the concentration of the compound in the solution was increased. The calculated inhibition efficiencies from the two investigated methods were in good agreement. Potentiostatic polarization measurements indicate that HNPU acts as a mixed‐type inhibitor. The adsorption of the inhibitor on the carbon steel surface obeys Langmuir adsorption isotherm. The values of activation energy and the thermodynamic parameters, such as adsorption equilibrium constant (K_ads), adsorption free energy (ΔG_ads), adsorption heat (ΔH_ads), and adsorption entropy (ΔS_ads) values were calculated and discussed. The results obtained from infrared spectra, confirmed the adsorption of inhibitor on the alloy surface after immersion in acidic solution containing HNPU. The SEM analysis indicated that there are more lightly corroded and oxidative steel surface for the specimens after immersion in acidic solution containing HNPU than that in blank.     

Electrochemical behavior of aluminium in acidic media

The inhibitive action of the acid extracts of seeds' leaves and bark from the Ficus virens plant towards hydrochloric and sulfuric acid corrosion of aluminium is tested using mass loss and thermometric techniques. It was found that the extract acts as a good corrosion inhibitor for aluminium corrosion in all concentration of hydrochloric and sulfuric acid solution. The ellagic acid has been used as a representative of the tannin species. The tannins are anodic inhibitors. The inhibition efficiency (IE) increases as the extract concentration is increased. The effect of temperature on the IE was studied. It was found that the presence of extract increases the activation energy of the corrosion reaction. Moreover, the heat of adsorption (Q_ads) was also calculated. It was found that the Ficus virens extract provides a good protection against pitting corrosion in chloride ion containing solution.     

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

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

Synthesis of imidazoline‐based dissymmetric bis‐quaternary ammonium gemini surfactant and its inhibition mechanism on Q235 steel in hydrochloric acid medium

An imidazoline‐based dissymmetric bis‐quaternary ammonium gemini surfactant has been synthesized. Its surface active properties at equilibrium in water at 25 °C were determined. The inhibitive effect of the compound on Q235 steel in 1 M hydrochloric solution was investigated by the weight‐loss method, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) analysis, and quantum chemical calculations. The results indicate that the compound has high surface properties and the inhibition efficiency (IE) increases with the increase in inhibitor concentration, which attain the maximum value around the CMC value. The imidazoline‐based dissymmetric bis‐quaternary ammonium acts as a mixed type inhibitor mainly inhibiting the cathodic processes and does not change the mechanism of either hydrogen evolution reaction or mild steel dissolution. The best IE is obtained at the immersion time of 144 h. The adsorption of the studied inhibitor on Q235 steel can be fitted to a Langmuir isotherm and the adsorption process is a spontaneous chemical adsorption. Quantum chemistry calculation results show that the imidazoline ring and heteroatoms of N, O, are the active sites of the inhibitors.     

Inhibition of aluminum corrosion using Opuntia extract

The inhibitive action of the mucilage extracted from the modified stems of prickly pears, toward acid corrosion of aluminum, is tested using weight loss, thermometry, hydrogen evolution and polarization techniques. It was found that the extract acts as a good corrosion inhibitor for aluminum corrosion in 2.0 M HCl solution. The inhibition action of the extract was discussed in view of Langmuir adsorption isotherm. It was found that the adsorption of the extract on aluminum surface is a spontaneous process. The inhibition efficiency (IE) increases as the extract concentration is increased. The effect of temperature on the IE was studied. It was found that the presence of extract increases the activation energy of the corrosion reaction. Moreover, the thermodynamic parameters of the adsorption process were calculated. It was found also that the Opuntia extract provides a good protection to aluminum against pitting corrosion in chloride ion containing solutions.     

Adsorption rate and protective effect of tributyl(cyclohexyl)ammonium chloride inhibitor on the acidic corrosion of steel

The inhibition of corrosion of a steel surface by an inhibitor, tributyl(cyclohexyl)ammonium chloride (TBCA), was investigated by gravimetric and electrochemical polarization measurements in various aqueous solutions of HCl and H₂SO₄ acids. It is known that the most extensive corrosive destruction proceeds during the initial stage of contact between the metallic surface and the aggressive surroundings. The change from H₂SO₄ to HCl considerably decreases the time for formation of an adsorption layer. The high adsorption of the surface‐active cationic TBCA on the steel electrode surface can be explained by the specific adsorption of Cl^? anions increasing the negative charge on the electrode surface. It was observed that the value of the polarizing current can be increased from time to time by addition of more TBCA inhibitor. This fact can be explained by the low stability of the film‐forming layer on the steel. A similar decrease of the protective effect was also observed in HCl solution. The inhibitor provides at least a slowing of the corrosion process (τ = 21 min). It was found that an increase in H₂SO₄ concentration from 1.0 to 0.2 N did not change the protective action of the inhibitor and had rather high values (θ = 283 ma/h, ψ = 84%, and τ = 14 min at [I] = 3.5 × 10^?4 mol/L). It was shown that the attraction constant has a negative value (A = ?1.5 and K_a = 22.3) for the inhibitor, which relates to a high value for the adsorption ability of TBCA in HCl solution and therefore with the intermolecular repulsive force between adsorption molecules having similar charges. The protective action of TBCA increases with an increase in temperature, which is correlated with the chemical nature of its adsorption on the steel surface.     

Investigation of the inhibition effect of 5-((E)-4-phenylbuta-1,3-dienylideneamino)-1,3,4-thiadiazole-2-thiol Schiff base on mild steel corrosion in hydrochloric acid

The inhibition effect of 5-((E)-4-phenylbuta-1,3-dienylideneamino)-1,3,4-thiadiazole-2-thiol (PDTT) Schiff base on mild steel corrosion in 0.5 M HCl was studied for both short and long immersion time. For this purpose, potentiodynamic polarization, electrochemical impedance spectroscopy, linear polarization resistance, hydrogen gas evolution, the change of open circuit potential as a function of immersion time, SEM and AFM techniques were utilized. The PDTT Schiff base has shown remarkable inhibition on the corrosion of mild steel in 0.5 M HCl solution. The high inhibition efficiency was attributed to the blocking of active sites by adsorption of inhibitor molecules on the steel surface.     

二氧化碳腐蚀缓蚀剂及其缓蚀机理的研究进展

首先分别论述了单组分缓蚀剂和复配型缓蚀剂的缓蚀机理,即不同类型的缓蚀剂在金属表面所具有的不同吸附过程。单组分缓蚀剂中特殊的分子基团在金属表面通过物理吸附、化学吸附或混合吸附过程起到缓蚀作用,复配型缓蚀剂在金属表面通过各组分间协同吸附或竞争吸附过程起到缓蚀作用,并指出了缓蚀机理的研究所存在的问题。然后,主要综述了近几年来国内外对用于二氧化碳腐蚀缓蚀剂的研究进展,包括咪唑啉衍生物、表面活性剂、季铵盐、有机胺和复配型缓蚀剂,结合缓蚀剂的分子结构和缓蚀效率等对其进行了阐述。介绍了几种用于二氧化碳腐蚀的新型缓蚀剂,如多活性位点有机化合物、硫醇、席夫碱和聚合物等。最后针对二氧化碳腐蚀环境的复杂性,对未来缓蚀剂及其缓蚀机理的研究方向进行了展望。     

Effectiveness of Croton cajucara Benth on corrosion inhibition of carbon steel in saline medium

Application of corrosion inhibitors is one of the most common practices for the protection of steel structures and their alloys in industry. Since metallic corrosion is a major cause of economic losses in the oil industry, the use of natural inhibitors is an alternative for sustainable technological development. In the present study the effectiveness of the hydroalcoholic extract of the plant species Croton cajucara Benth (CC) dissolved in a microemulsion system (MES‐CC) as well as in dimethyl sulfoxide (DMSO‐CC) was evaluated as corrosion inhibitor on carbon steel AISI 1020 in saline medium. Surface tension measurements of the MES‐CC confirmed micelle formation, and rheological data showed that viscosity varies with temperature. According to potentiodynamic technique and Tafel extrapolation, maximum inhibition efficiencies were effective (93.84% for MES‐CC and 64.73% for DMSO‐CC) with predominant control of cathodic reaction. The adsorption of MES‐CC on carbon steel surface obeys Langmuir adsorption isotherm, while DMSO‐CC was found to follow the Frumkin isotherm.     

硫酸介质中榕树叶提取液的缓蚀性能及其与 KI 的缓蚀协同效应

通过电化学方法和失重法,研究了榕树叶提取液(FLE)对碳钢在硫酸溶液中的缓蚀性能,同时研究了它与KI的缓蚀协同效应,探讨了缓蚀机理。研究结果表明:在硫酸溶液中,FLE对碳钢属混合抑制型缓蚀剂,缓蚀效率随其浓度的增加而增大;FLE与KI之间存在良好的协同效应,两者复配后,体系的腐蚀电流密度减小,电荷传递电阻增大,双电层电容减小,缓蚀效率增大,表现出更好的缓蚀作用;FLE与KI复配前后,其在碳钢表面的吸附均为自发过程,且符合Langmuir吸附等温方程。     

Electrochemical studies on the effect of (2E)‐3‐amino‐2‐phenylazo‐but‐2‐enenitrile and its derivative on the behaviour of copper in nitric acid

The objective of this work is to provide additional insight on the influence of (2E)‐3‐amino‐2‐phenylazo‐but‐2‐enenitrile and its derivative as corrosion inhibitors for copper in 0.5 M HNO₃. Electrochemical techniques (potentiodynamic polarization, polarization resistance and impedance spectroscopy) as well as weight loss measurements have been employed to study the corrosion inhibition. The investigated compounds have shown inhibition efficiency in 0.5 M HNO₃. Inhibition efficiency of these compounds has been found to vary with the concentrations of the compounds. The adsorption of these compounds on the copper surface from the acid solution has been found to obey Langmuir adsorption isotherm. The results revealed that the compounds are mixed type inhibitors. The effect of temperature on the inhibition efficiency was studied.     

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

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

Copper corrosion inhibition by polyaspartic acid and imidazole

This work reveals the corrosion inhibition effect of polyaspartic acid (PASP) and imidazole (IM) on copper in 3 wt% aminosulfonic acid acting as mixed‐type inhibitor of predominant cathodic effect. Potentiodynamic polarization and electrochemical impedance spectroscopy work prove that at 30 °C, 1.0 g/L PASP alone gave the best inhibitory effect of 89.8%; the inhibition efficiency could reach up to 95.4% when combining PASP and IM at the same ratio in total of 1.0 g/L. The anti‐corrosion mechanism of PASP and IM on copper is proposed from the characteristic molecular structures of these two chemicals.     

2,4-二氨基嘧啶对冷轧钢在HCl溶液中的缓蚀作用

通过浸泡试验、电化学试验和扫描电子显微镜(SEM)观察研究了2,4-二氨基嘧啶(DAP)在1.0mol/L HCl溶液中对冷轧钢的缓蚀作用。结果表明:DAP在HCl溶液中对冷轧钢具有良好的缓蚀作用;缓蚀率随缓蚀剂含量的增大而增大,DAP浓度为10.0mmol/L时缓蚀率最大,可达94.8%;DAP为混合型抑制型缓蚀剂,DAP在冷轧钢表面的吸附符合Langmuir吸附等温式,缓蚀率随温度的升高而下降。