Thermodynamic,adsorption and electrochemical studies for corrosion inhibition of carbon steel by henna extract in acid medium

Corrosion inhibition of carbon steel in the presence of different concentrations of aqueous extract from henna leaves in 1 M HCl solution has been studied using the weight loss and potentiodynamic polarization techniques. The effect of temperature on the corrosion behavior of carbon steel was studied in the temperature range 293–333 K. The inhibition efficiency increases with increasing inhibitor concentration but decreases with increasing temperature. The activation and free energies for the inhibition reactions support the mechanism of physical adsorption. The adsorption of henna extract on C-steel surface is endothermic, spontaneous and consistent with the Langmuir adsorption isotherm. The potentiodynamic polarization measurements indicate that henna extract acts as a mixed inhibitor. Surface and protective film analysis have been carried out using; energy dispersive X-ray (EDX), scanning electron microscopy (SEM), Fourier transforms infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) analysis.     

Novel naphthenate surfactants based on petroleum acids and nitrogenous bases as corrosion inhibitors for C1018-type mild steel in CO2-saturated brine

The efficiency of two natural naphthenate surfactants (Naphthenic-dimethylamine and Naphthenic-diethylamine complexes), as corrosion inhibitors for mild steel in CO₂-saturated 1% NaCl solution, has been determined by linear polarization resistance corrosion rate and potentiodynamic polarization measurements. These compounds inhibit corrosion even at very low concentrations (25 ppm), and Naphthenic-diethylamine complex is the best inhibitor giving maximum inhibition efficiency (99.76) at 100 ppm. Polarization curves indicate that, the two investigated compounds are mixed inhibitors, affecting both cathodic and anodic corrosion currents. Adsorption of naphthenate surfactants on the mild steel surface is in good agreement with the Langmuir adsorption isotherm model, and the calculated Gibbs free energy values confirm the chemical nature of the adsorption. Energy dispersive X-ray fluorescence microscopy (EDRF) and scanning electron microscope (SEM) observations confirmed the existence of such an adsorbed film on the mild steel surface.     

A3钢在海洋环境腐蚀行为的电偶法研究

在海洋腐蚀模拟试验机中测定了A3钢分别挂片和电连接挂片处于大气区、飞溅区、潮差区和全浸区的腐蚀速度以及在介质不同运动状况（海浪）下试片的电偶电位、电偶电流、自腐蚀电位。试验结果与用宏腐蚀电池理论对电连接挂片和分别挂片在海洋环境中不同的腐蚀规律的阐释相吻合，为海洋环境中碳素结构钢的腐蚀与防护提供参考。     

Adsorption and inhibition behavior of a novel Schiff base on carbon steel corrosion in acid media

In this study, the inhibition effect of 2,2′-(heptane-1,7-diylbis(azanylylidene)bis-(methanylylidene))diphenol (HAMD) on carbon steel corrosion in 0.5 mol L⁻¹ H₂SO₄ solution was studied. Weight loss and electrochemical techniques such as open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to inspect the efficiency of HAMD as corrosion inhibitor. Scanning electron microscopy (SEM) and energy dispersion X-ray (EDAX) were used to characterize the steel surface. Polarization measurements indicated that, the studied inhibitor acts as mixed-type inhibitor. The adsorption of HAMD molecules on the carbon steel surface obeys Langmuir adsorption isotherm.     

Corrosion protection of mild steel by a new phosphonate inhibitor system in aqueous solution

A protective film has been developed on the surface of the mild steel in low chloride aqueous environment using a synergistic mixture of an eco friendly inhibitor, imino dimethyl phosphonic acid (IDMPA) and Zn²⁺. The synergistic effect of IDMPA in controlling corrosion of the mild steel has been investigated by gravimetric and electrochemical studies in the presence of Zn²⁺. The formulation consisting of IDMPA and Zn²⁺ has excellent inhibition efficiency. The mixed mode of inhibition studied by potentiodynamic polarization and electrochemical impedance spectroscopy has shown that the changes in the impedance parameters like charge transfer resistance (R_ct) and constant phase element (CPE) confirm the strong adsorption on the mild steel. Surface characterization inspection using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) is used to ascertain the nature of the protective film. The mechanistic aspects of corrosion inhibition are proposed.     

The performance of hydrophobic and hydrophilic moieties in synthesized thiol cationic surfactants on corrosion inhibition of carbon steel in HCl

Here in, cationic surfactants namely (1-octyl, decyl, and dodecyl-4-mercaptopyridine-1-ium bromide) I, II and III, respectively, were synthesized. The inhibition effect of these surfactants on the corrosion of carbon steel in 1 M HCl was studied by polarization, electrochemical impedance spectroscopy (EIS) and weight loss measurements. Polarization curves revealed that the used inhibitors represent mixed-type inhibitors. Adsorption of used inhibitors led to a reduction in the double layer capacitance and an increase in the charge transfer resistance. Adsorption of used compounds was found to obey Langmuir isotherm.     

Inhibition of mild steel corrosion and calcium sulfate formation in highly saline synthetic water by a newly synthesized anionic carboxylated surfactant

A newly anionic surfactant; namely (2Z,2′Z)-4,4′-(ethane-1,2-diylbis((2-((4-dodecylphenyl)sulfonamido)ethyl)azanedinyl)bis(4-oxobut-2enoate), desined as Tetra-anionic surfactant was synthesized. Its chemical structure was confirmed by FTIR and ¹HNMR spectroscopic techniques. The corrosion mitigation behavior of the prepared surfactant for mild steel (MS) in high saline synthetic water was monitoring by chemical technique (weight loss), electrochemical techniques (Tafel and EIS). The obtained results showed that the corrosion resistance has been improved after the addition of the surfactant molecules. The inhibition efficiency grown up with the inhibitor concentration reaching the maximum at concentration 120?ppm, where the IE% values were 84, 82, and 79.5% in cases of weight loss, Tafel and EIS techniques, respectively. The mixed-type inhibitor with permanent anodic effect can be inferred from polarization data of mild steel in the presence of different concentration of Tetra- compound. The corrosion protection performance of the used inhibitor was related to its adsorption ability on the MS surface. The adsorption of Tetra-molecules increased the charge transfer resistance of MS. The adsorption process of the tested corrosion inhibitor obeyed Langmuir adsorption isotherm. The corrosion and scale produced layer formed on the mild steel surface in absence and presence of the insight anionic surfactant was depicted by SEM. The chemical analysis of this layer was examined by EDX, and show the corrosion and Ca- scale inhibition performance of Tetra- molecules. Quantum chemical calculations were compatible with the experimental results.     

Effects of alternating current interference on corrosion of X60 pipeline steel

With rapid economic development in China, demand for energy and transportation is growing. Due to the limitations of factors such as terrain and traffic, a large number of buried oil and gas pipelines are parallel to highvoltage transmission lines and electrified railways over long distances. Alternating current (AC) corrosion of pipelines is very serious in such cases. In this work, laboratory experiments were carried out with an electrochemical method in a simulated soil solution at various AC current densities from 0 to 200 A/m2 and AC frequencies from 10 to 200 Hz. Experimental results indicated that with an increase in the AC current density, the corrosion potential of an X60 steel electrode shifted negatively, the anodic current density increased significantly, and the corrosion rate increased. Moreover, with an increase in the AC frequency, the corrosion potential of the X60 electrode shifted positively and the anodic current density decreased, which led to a decrease in the corrosion rate. Furthermore, the morphology of X60 electrodes indicated that uniform corrosion occurred at a low AC current density; while corrosion pits were found on the X60 electrode surface at a high AC current density, and deep corrosion pits seriously damaged the pipelines and might lead to leakage.     

High-temperature hydrogen sulfide corrosion on the heat-affected zone of the AISI 444 stainless steel caused by Venezuelan heavy petroleum

The aim of this study was to evaluate the effect of welding on the corrosion resistance of the heat-affected zone (HAZ) of the AISI 444 ferritic stainless steel in medium containing Venezuelan heavy oil. AISI 444 steel plates were welded through the use of three levels of welding heat input (4, 6 and 8 kJ/cm). Samples were extracted from the welded plates and thermally treated in three different temperatures (200, 300 e 400 °C), while immerged in petroleum for a period of 4 h. Optical microscopy (OM), scanning electronic microscopy (SEM) and energy dispersive X-ray analysis (EDX) techniques were used for the analysis of the surface and transversal section of the joint. Electrochemical trials of cyclic potentiokinetic reactivation of double loop (EPR-DL) were also carried out. It has been concluded that the temperature of treatment has direct influence on the level of material corrosion and that the increase in the welding heat input contributes to a higher level of corrosion.     

X90管道钢在NS4溶液中的电化学腐蚀行为

由于油气管道敷设于地下,在敷设过程中管道会经过不同的地区,从而遭受不同程度的腐蚀,严重的可能导致管道开裂,造成巨大的人员伤亡和经济损失。因此,开展管道钢在模拟土壤环境中的电化学腐蚀行为研究,对于保证油气管道的安全运行具有重要的意义。为此,采用电化学阻抗技术(EIS)和动电位极化测试技术,研究了X90管道钢直缝焊管母材和焊缝在近中性模拟土壤溶液(NS4)中的电化学腐蚀行为。结果表明:1在NS4溶液中,X90管道钢具有典型的阳极溶解特征,没有钝化现象;2母材的热力学稳定性高于焊缝的热力学稳定性;3在-850 m V极化电位下对母材和焊缝试样进行不同时间的极化,随着极化时间的延长,材料的极化电阻增加,腐蚀电流密度下降,材料的耐蚀性增加且母材的耐蚀性优于焊缝。     

高酸性条件下元素硫对碳钢腐蚀的影响

天然气中硫含量超过一定温度、压力条件下的溶解度会导致气井中发生硫沉积,当元素硫大量沉积时,会堵塞流体通道.导致关井停产以及采输系统的严重腐蚀。为此,采用电化学极化测试、电化学阻抗测试和失重腐蚀及应力腐蚀测试的组合体系,全面系统地开展了元素硫存在条件下碳钢的腐蚀性能试验,进而模拟了元素硫在现场可能出现的沉积方式,弄清了元素硫沉积量、沉积方式对碳钢腐蚀性能的影响及腐蚀垢物的组成。结果表明:①元素硫与试样的接触程度和堆积形式对碳钢的腐蚀行为有重要影响;②元素硫的存在促进了碳钢的阴极反应;③硫的加入会改变腐蚀产物膜的结构,降低膜的电阻,增大腐蚀速率。最后结合电化学及失重腐蚀测试结果,明确了碳钢在含氯化物湿硫化氢环境中的腐蚀机理,为元素硫沉积工况下的材质选择、缓蚀剂应用、腐蚀监测及控制提供了技术支撑。     

Magnetite nanoparticles/polyvinyl pyrrolidone stabilized system for corrosion inhibition of carbon steel

The corrosion inhibitive effects of new polyvinylpyrrolidone stabilized crystalline super-paramagnetic nanoparticles (5–20?nm) were investigated. Several characterization techniques confirmed the high stability of the prepared stabilized nanoparticles in solution. The polarization and EIS measurements showed that the inhibition efficiency increased with increasing concentration of the magnetite nanoparticles. The results obtained from EIS and electrochemical polarization curves are in reasonably good agreement. The obtained results suggest that the prepared stabilized system is an excellent inhibitor for carbon steel corrosion in 1?M HCl solution.     

Investigation of a few oxazolone molecules as corrosion inhibitor for API5LX60 steel in 1N H2SO4 solution

Corrosion is recognized as a notable problem in oil sector where API5LX60 steel transmission pipelines are in frequent use. In this report, three oxazolone derivatives as potential corrosion inhibitors were investigated on API5LX60 graded carbon steel in 1N H₂SO₄ solution in stagnant conditions at concentrations 50–200 ppm. Gravimetric weight loss coupons and electrical resistance corrosion monitoring techniques performed on test samples showed inhibitory properties with best at 200 ppm inhibitor concentration. The results further revealed that the degree of inhibition was concentration dependent. Inhibitor I exhibited the highest inhibition efficiency of 90.70% at 200 ppm concentration. Statistical analysis using multiple linear regression model procreated high R² value of 0.998 and p-value < 0.0001 asserting a smooth linear dependence of inhibitor efficiency on oxazolone concentration and weight loss of the steel. Again, surface analysis affirmed the formation of protective coating of inhibitor on steel surface. Furthermore, the oxazolone inhibitor adsorbed physically on the steel surface and obeyed the Langmuir isotherm which is evident from the linear correlation coefficient value of 0.9992.     

13Cr不锈钢的CO_2腐蚀行为研究

试验研究了在模拟现场环境下 ,13Cr不锈钢中 1Cr13、2Cr13、HP13Cr在高温高压下的CO2 腐蚀行为。结果表明 ,3种材料平均腐蚀速率的对比结果为 2Cr13>1Cr13>HP13Cr。当温度为 15 0℃时 ,3种材料的平均腐蚀速率达到最大。CO2 分压和流速增大 ,材料的平均腐蚀速率随之增大。当Cl-浓度为 10× 10 -6～ 10 0 0 0× 10 -6时 ,平均腐蚀速率随着Cl-浓度的增大而增大 ,当Cl-浓度超过 10 0 0 0× 10 -6后 ,平均腐蚀速率随着Cl-浓度的增大而稍有下降。     

Phytochemical screening and corrosion inhibitive behavior of Pterolobium hexapetalum and Celosia argentea plant extracts on mild steel in industrial water medium

Preliminary phytochemical screening was carried out for methanolic extracts of Pterolobium hexapetalum (PH) and Celosia argentea (CA). Methanolic extracts of PH and CA were studied as corrosion inhibitors for mild steel in industrial water medium using mass loss and electrochemical techniques. The adsorption of both PH and CA extracts on mild steel surface followed Langmuir isotherm. The electrochemical impedance spectroscopy (EIS) measurements showed that the charge transfer resistance increases with increasing concentration of extracts. Various thermodynamic parameters were evaluated and discussed. Scanning electron microscopy (SEM) was used to analyze the surface adsorbed film. Further, antioxidant activity of the plant extracts was determined and correlated with the results obtained with inhibition efficiency.     

Comparative studies on the electrochemical and physicochemical behaviour of three different benzimidazole motifs as corrosion inhibitor for mild steel in hydrochloric acid

This paper examines the anticorrosion characteristics of three different benzimidazole derivatives towards mild steel in 0.5?M hydrochloric acid at temperature ranges from 303 to 323?K. The benzimidazole derivatives used for the screening studies are 2-(2-methyl-1H-benzimidazol-1-yl) acethydrazide (EMBAH), 2-(2-ethyl-1H-benzimidazol-1-yl) acethydrazide (EEBAH) and 2-(2-propyl-1H-benzimidazol-1-yl) acethydrazide (EPBAH). The corrosion inhibition was investigated by weight loss, electrochemical impedance spectroscopy and potentiodynamic polarization studies. The adsorption interaction between metal and inhibitor followed Langmuir adsorption isotherm. The Gibb’s free energy values clarify the spontaneous nature of adsorption process. The temperature dependence of inhibition efficiency was explained by considering thermodynamic parameters of adsorption and kinetic parameters of corrosion. These inhibitors showed good efficiency at lower as well as moderately higher temperatures. Quantum chemical calculations were done using DFT at the B3LYP/6-31G¹ level to study the electronic properties of the molecules for correlating the inhibitive effect and molecular structure.     

沉积物下碳钢的腐蚀试验研究

针对油田集输管线经常发生的腐蚀穿孔现象，通过室内模拟试验，探讨管道内壁沉积物对管道腐蚀的影响，测定了表面有、无沉积物时碳钢电极的自腐蚀电位与时间的关系，采用电偶法和静态挂片法，测定了有、天沉积物时碳钢的腐蚀速率。试验表明：表面有沉积物时，碳钢自腐蚀电位负移、自腐蚀速率减小；表面有沉积物的电极与没有沉积物的电极短接将形成氧浓差腐蚀电池，加速表面有沉积物电极的腐蚀。