ANISALIDINE DERIVATIVES AS CORROSION INHIBITORS OF MILD STEEL IN ACIDIC MEDIA. 1

The corrosion inhibitory properties on mild steel in acidic media by nitrogen-containing ligands N-(4-nitro phenyl) p-anisalidine (SB1), N-(4-chloro phenyl) p-anisalidine (SB2), N-(4-phenyl) p-anisalidine (SB3), N-(4-methoxy phenyl) p-anisalidine (SB4), and N-(4-hydroxy phenyl) p-anisalidine (SB5) have been studied using mass loss, thermometric, and potentiostatic polarization techniques. Due to adsorption of the additive molecules on the metal surface the inhibition efficiency increases up to 98.85% with increasing additive concentration. A synergistic effect exists between the Schiff base additives and mild steel. The mechanistic effect of corrosion inhibition has been investigated by the potentiostatic polarization technique. The impact of temperature on the performance of these compounds clearly shows the effect of the decomposition and desorption of these compounds at higher temperatures.     

CHAMOMILE (Matricaria recutita) EXTRACT AS A CORROSION INHIBITOR FOR MILD STEEL IN HYDROCHLORIC ACID SOLUTION

The corrosion inhibition of mild steel in hydrochloric acid solution by chamomile (Matricaria recutita) extract (CE) was investigated through electrochemical (polarization, EIS) and surface analysis (optical microscopy/AFM/SEM) techniques. The effects of inhibitor concentration, temperature, and pH were evaluated. Thermodynamic parameters were calculated and adsorption studies were carried out. Finally, the surface morphology was investigated. The electrochemical studies showed that CE acts as a mixed-type corrosion inhibitor with predominantly anodic behavior. CE was adsorbed physically on the metal surface and obeyed the Langmuir adsorption isotherm. It impeded the corrosion processes by changing the activation energy. In the presence of CE, the metal surface was more uniform than the surface in the absence of inhibitor. Maximum inhibition efficiency (IE) was 93.28%, which was obtained at 22°C in 7.2 g/L of inhibitor in 1 M HCl solution.     

LOW MOLECULAR WEIGHT STRAIGHT-CHAIN DIAMINES AS CORROSION INHIBITORS FOR SS TYPE 304 IN HCL SOLUTION

The effect of some low molecular weight straight-chain diamines to inhibit the corrosion of SS type 304 in 1 M HCl solution is examined by weight loss and galvanostatic polarization techniques. The inhibition efficiency increases with increasing the number of carbon atoms in the chain up to 8 carbons, but at higher than 8 carbon atoms (12 carbons) it decreases again. These diamine compounds act as mixed-type inhibitors, but the cathode is more polarized than the anode when an external current was applied. The corrosion rate in the presence of the investigated diamine compounds was found to increase with increasing the temperature and decrease with increasing the concentration of these compounds. Activation parameters for the corrosion of SS in 1 M HCl were calculated and showed that corrosion was much reduced in the presence of inhibitors. The adsorption of these compounds on SS from 1 M HCl solution obeys the Langmuir adsorption isotherm. The synergistic effect of KI on the inhibitive efficiency of the investigated diamine compounds was also studied.     

LOW MOLECULAR WEIGHT STRAIGHT-CHAIN DIAMINES AS CORROSION INHIBITORS FOR SS TYPE 304 IN HCL SOLUTION

The effect of some low molecular weight straight-chain diamines to inhibit the corrosion of SS type 304 in 1 M HCl solution is examined by weight loss and galvanostatic polarization techniques. The inhibition efficiency increases with increasing the number of carbon atoms in the chain up to 8 carbons, but at higher than 8 carbon atoms (12 carbons) it decreases again. These diamine compounds act as mixed-type inhibitors, but the cathode is more polarized than the anode when an external current was applied. The corrosion rate in the presence of the investigated diamine compounds was found to increase with increasing the temperature and decrease with increasing the concentration of these compounds. Activation parameters for the corrosion of SS in 1 M HCl were calculated and showed that corrosion was much reduced in the presence of inhibitors. The adsorption of these compounds on SS from 1 M HCl solution obeys the Langmuir adsorption isotherm. The synergistic effect of KI on the inhibitive efficiency of the investigated diamine compounds was also studied.     

SYNTHESIS,CHARACTERIZATION, AND COMPARATIVE STUDY OF PYRIDINE DERIVATIVES AS CORROSION INHIBITORS OF MILD STEEL IN HCl MEDIUM

Radical catalysis has been used to achieve addition of dodecanethiol and mercaptoacetic acid to 4-vinylpyridine (4VP), giving 4-(dodecylthiaethyl)pyridine (DTEP) and 4-pyridylethylthia-acetic acid (PETAA). The purified monoadducts have been characterized using ¹H NMR and ¹³C NMR spectroscopy. Inhibition of the corrosion of mild steel in 1 M HCl by 4VP, DTEP, and PETAA has been investigated at 308 K using weight loss measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) methods. The results obtained show that PETAA is the best inhibitor and its inhibition efficiency (E %) increases with the inhibitor concentration, reaching up to 93% for DTEP at 10^?3 M. Potentiodynamic polarization studies clearly revealed that the inhibitors changed the mechanism of hydrogen evolution and that they acted as mixed inhibitors but most effectively in the cathodic range.     

INVESTIGATION OF ADSORPTION AND INHIBITIVE PROPERTIES OF SOME DIAMINE COMPOUNDS ON MILD STEEL CORROSION IN HYDROCHLORIC ACID SOLUTION

In this work, the adsorption and corrosion inhibition effect of two new synthesized compounds on mild steel in 6 M hydrochloric acid was studied by electrochemical impedance spectroscopy, Tafel polarization, weight loss, quantum, and atomic force microscopy methods. The obtained results show that these compounds are efficient corrosion inhibitors for mild steel in hydrochloric acid media. Electrochemical impedance spectroscopy shows that inhibition efficiency increases with increase of concentration of both inhibitors. These molecules obey the Langmuir adsorption isotherm. Some samples of mild steel were examined by atomic force microscopy. Quantum chemical calculations were further applied to reveal the adsorption structure and explain the experimental results.     

TERTIARY KETONIC MANNICH BASES AS CORROSION INHIBITORS FOR ALUMINUM DISSOLUTION IN ACIDIC SOLUTIONS

Aluminum corrosion rate was studied in the absence and presence of some tertiary ketonic Mannich bases in 2 M HCl solution, using weight loss and galvanostatic polarization techniques. The two methods gave similar results. The results showed that the inhibitor efficiency increases with increasing inhibitor concentration and decreases with increasing the temperature of the system. The adsorption of these Mannich bases on Al surface is found to obey Temkin's adsorption isotherm. Galvanostatic polarization studies showed that these compounds are mixed-type inhibitors. Some thermodynamic parameters were computed and discussed. Finally, the influence of the chemical structure of the tertiary ketonic Mannich bases on their inhibition efficiencies is discussed.     

BIOMASS EXTRACTS FOR MATERIALS PROTECTION: CORROSION INHIBITION OF MILD STEEL IN ACIDIC MEDIA BY Terminalia chebula EXTRACTS

The inhibiting action of the fruit extract of Terminalia chebula (TC) on mild steel corrosion in 1 M HCl solution was studied using gravimetric, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. The experimental results showed that TC functioned as an inhibitor in the acidic corrodent and that corrosion inhibition efficiency increased with extract concentration. Cathodic and anodic polarization curves show that TC functioned as a mixed-type inhibitor, while impedance results show that the extract organic matter was adsorbed at the metal/corrodent interphase. A computational study of the adsorption behavior of some of the organic constituents of the extracts was carried out using density functional theory (DFT). The computations were used to theoretically ascertain the individual contributions of the constituents to the observed corrosion-inhibiting effect of the extract.     

迁移性阻锈剂——钢筋混凝土阻锈剂的新发展

介绍了钢筋混凝土阻锈剂的基本概念和发展背景，比较讨论了新发展起来的迁移性阻锈剂与传统的亚硝酸盐阻锈剂性能特点，根据作者对迁移性阻锈剂的电化学测试和文献资料中的研究结果，着重分析了迁移性阻锈剂对钢筋电化学性能的影响和阻锈机理，最后提出了迁移性阻锈剂应用技术的发展前景和有待深入研究的课题。     

THE EFFECT OF ENVIRONMENTALLY BENIGN FRUIT EXTRACT OF SHAHJAN (MORINGA OLEIFERA) ON THE CORROSION OF MILD STEEL IN HYDROCHLORIC ACID SOLUTION

The inhibition of the corrosion of mild steel in hydrochloric acid solution by the fruit extract of shahjan (Moringa oleifera) was studied using weight loss, electrochemical impedance spectroscopy (EIS), linear polarization, and potentiodynamic polarization techniques (Tafel). Inhibition was found to increase with increasing concentration of the extract. The effect of temperature, immersion time, and acid concentration on the corrosion behavior of mild steel in hydrochloric acid solutions with addition of extract was also studied. The inhibition occurred via adsorption of the inhibitor molecules on the mild steel surface obeying the Langmuir adsorption isotherm. Thermodynamic activation parameters such as activation energy, enthalpy (ΔH*), and entropy (ΔS*) of activation for corrosion process were calculated and discussed. The results obtained show that both chemical and physical adsorption of inhibitor molecules occur simultaneously and the fruit extract of shahjan (Moringa oleifera) could serve as an effective inhibitor of the corrosion of mild steel in hydrochloric acid media.     

Electrochemical and quantum chemical study of purines as corrosion inhibitors for mild steel in 1 M HCl solution

The purines and its derivatives, such as, guanine, adenine, 2,6-diaminopurine, 6-thioguanine and 2,6-dithiopurine, were investigated as corrosion inhibitors for mild steel in 1 M HCl solution by weight loss measurements, electrochemical tests and quantum chemical calculations. The polarization curves of mild steel in the hydrochloric acid solutions of the purines showed that both cathodic and anodic processes of steel corrosion were suppressed. The Nyquist plots of impedance expressed mainly as a depressed capacitive loop with different compounds and concentrations. For all these purines, the inhibition efficiency increased by increasing the inhibitor concentration, and the inhibition efficiency orders are 2,6-dithiopurine > 6-thioguanine > 2,6-diaminopurine > adenine > guanine with the highest inhibiting efficiency of 88.0% for 10⁻³ M 2,6-dithiopurine.The optimized structures of purines, the Mulliken charges, molecular orbital densities and relevant parameters were calculated by quantum chemical calculations. The quantum chemical calculation results inferred that the adsorption belong to physical adsorption, which might arise from the π stacking between the π electron of the purines and the metal surface.     

低碳钢在NaCl水溶液中闭塞区内化学状态的变化

用模拟闭塞电池恒电流实验研究了低碳钢(A3钢)在0.o1mo·L~(-1)NaCl溶液中闭塞区内化学状态的变化.对内试件通入阳极电流后,闭塞区内溶液pH值随时间的延长和电量的增加而迅速下降,当pH值约为6之后下降缓慢,pH值与电量的对数呈直线关系.CI~-向闭塞区内电迁移,每迁入Cl~-1 mol需要电量1.5～1.6F(法拉第),该关系不随时间长短和电流密度大小而变化.     

TAURINE AS A GREEN CORROSION INHIBITOR FOR AISI 4130 STEEL ALLOY IN HYDROCHLORIC ACID SOLUTION

The inhibition ability of 2-aminoethanesulfonic acid (taurine) against the corrosion of AISI steel 4130 in 1 M HCl solution was evaluated by polarization, impedance (EIS), and chronoamperometry. Polarization studies indicated that taurine retards both cathodic and anodic reactions through chemical adsorption and blocking the active corrosion sites. The adsorption of this compound obeyed the modified Langmuir adsorption isotherm. EIS data shows that as the inhibitor concentration increased, the charge transfer resistance of steel increased, while double layer capacitance decreased. Kinetic and thermodynamic parameters such as activation energy, enthalpy, entropy, and free energy of activation and adsorption were calculated. Gibbs free energy indicated that the adsorption process is spontaneous. Atomic force microscopy (AFM) and optical microscopy were used to study the steel surface. Surface studies show that the surface of a sample in solution with inhibitor molecules looks more uniform, with less roughness, than that in the uninhibited solution. Results obtained from quantum chemical studies show excellent correlations between quantum chemical parameters and experimental inhibition efficiencies using density functional theory (DFT).     

INHIBITION OF MILD STEEL CORROSION IN SULFURIC ACID MEDIUM BY HYDROXYETHYL CELLULOSE

The inhibitive effect of hydroxyethyl cellulose (HEC) on mild steel corrosion in aerated 0.5 M H₂SO₄ solution was studied using gravimetric and electrochemical techniques. The effect of temperature on corrosion and inhibition was also investigated. The results show that hydroxyethyl cellulose functioned as a good inhibitor in the studied environment and inhibition efficiency increased with concentration of inhibitor. Potentiodynamic polarization measurements revealed that HEC inhibited both the cathodic and anodic partial reactions of the corrosion processes. Impedance results clearly show that HEC inhibited the corrosion reaction by adsorption onto the metal/solution interface by significantly decreasing the double layer capacitance (C _dl ). This result was greatly pronounced in the presence of the inhibitor system (HEC + KI) that contains halide additive. Temperature studies revealed an increase in inhibition efficiency with rise in temperature. The adsorption behavior was found to obey the Freundlich isotherm. The values of activation energy, heat of adsorption, and standard free energy suggest that there was transition from physical to chemical adsorption mechanism of HEC on the mild steel surface. Quantum chemical calculations using the density functional theory (DFT) was employed to determine the relationship between molecular structure and inhibition efficiency.     

Effect of Forced Periodical Perturbation on Stability of Hydrodynamic States and Gas-Liquid Mass Transfer in a Trickle Bed

The stability of the hydrodynamic states corresponding to the operation on two branches of the hysteresis loop of pressure drop was examined for a trickle bed. The effect of nonsteady operation on the pressure drop and the gas-liquid mass transfer rate was investigated with several types of periodical perturbation on gas flow rate. It is found that the pressure drop and mass transfer coefficient obtained during operation under the conditions of the lower branch can be increased up to or even beyond those obtained by following the upper branch of the loop without necessarily traversing along the loop to pass through the pulsing point. These results shed light on the mechanism of performance enhancement by periodical operation of trickle beds and might provide a possible way to improve the operation of trickle bed reactors.     

Molecular simulation, quantum chemical calculations and electrochemical studies for inhibition of mild steel by triazoles

The inhibition performance of three triazole derivatives on mild steel in 1 M HCl were tested by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The adsorption behavior of these molecules at the Fe surface was studied by the molecular dynamics simulation method and the quantum chemical calculations. Results showed that these compounds inhibit the corrosion of mild steel in 1 M HCl solution significantly. Molecular simulation studies were applied to optimize the adsorption structures of triazole derivatives. The iron/inhibitor/solvent interfaces were simulated and the charges on the inhibitor molecules as well as their structural parameters were calculated in presence of solvent effects. Aminotriazole was the best inhibitor among the three triazole derivatives (triazole, aminotriazole and benzotriazole). The adsorption of the inhibitors on the mild steel surface in the acid solution was found to obey Langmuir's adsorption isotherm.     

BENEFICIAL ROLE OF SURFACTANTS AS CORROSION INHIBITORS IN PETROLEUM INDUSTRY: A REVIEW ARTICLE

The objective of this review is to outline the beneficial role of surfactants as corrosion inhibitors in the petroleum field. After an introduction and brief notes on fundamentals of surfactants, the article shows the most important corrosion problems in the oil industry and the effective role of surfactants to solve these problems. The reported mechanisms of corrosion inhibition by surfactants are also considered. Key results are extracted from publications covering the past 50 years.     

工业纯铁/盐酸体系中聚丙烯酸的缓蚀作用机理

利用稳态极化曲线测量和恒电位方波测极化阻力Rp 的方法研究了聚丙烯酸 (PAAC)在工业纯铁 / 0 .5mol·L-1HCl中的缓蚀行为及其吸附特征 .结果表明 ,PAAC作为阻滞剂参与并阻滞了铁在盐酸溶液中的阳极溶解过程 ,但对阴极过程几乎无作用 .推导了PAAC参与并阻滞铁的阳极溶解过程的动力学方程 ,提出了相应的缓蚀机理 .     

CORROSION INHIBITION OF STEEL PIPELINES IN OIL WELL FORMATION WATER BY A NEW FAMILY OF NONIONIC SURFACTANTS

A new family of nonionic surfactants was synthesized and evaluated as corrosion inhibitors for steel pipelines in oil well formation water. Polarization data show that the selected surfactants act as mixed-type inhibitors. EIS results show that the change in impedance parameters (R_t and C_dl) with the concentration of the surfactants studied is indicative of the adsorption of surfactant molecules on carbon steel surface, leading to formation of a good protective film. The properties of this film were studied by various surface analysis tools. Finally, the relation between the surface properties of the inhibitor molecules and corrosion inhibition efficiency is discussed.