Benevolent behavior of Kleinia grandiflora leaf extract as a green corrosion inhibitor for mild steel in sulfuric acid solution

The ethanolic extract of Kleinia grandiflora leaves was characterized and tested for its potential anticorrosion properties on mild steel in 1 M H2SO4 medium using mass-loss analysis, potentiodynamic polarization measurements, electrochemical impedance spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, UV–visible spectroscopy, and X-ray diffraction analysis. The effect of temperature on the corrosion behavior of mild steel was studied in the range of 308 to 328 K. The inhibition efficiency was observed to increase with increasing concentration of the extract. Polarization curves revealed that the Kleinia grandiflora leaf extract is a mixed inhibitor. Impedance diagrams revealed that an increase of Kleinia grandiflora leaf extract concentration increased the charge transfer resistance and decreased the double-layer capacitance. The adsorption process obeys Langmuir＇s model, with a standard free energy of adsorption（ΔGads） of-18.62 k J/mol. The obtained results indicate that the Kleinia grandiflora leaf extract can serve as an effective inhibitor for the corrosion of mild steel in a sulfuric acid medium.

Concentration Boundary Layer Model of Mortar Corrosion by Sulfuric Acid

A long time immersion experiment of mortar specimens is carried out to investigate their degradation mechanism by sulfuric acid.Water-cement ratios of mortar are ranging from 0.5 to 0.7 and the pH value of sulfuric acid is 3.5 and 4.0 respectively.The pH meter is used to monitor the soak solution and the titration sulfuric acid with given concentration is added to maintain original pH value,through which the acid consumption of mortar is recorded.A theoretical reaction rate model is also proposed based on concentration boundary layer model.The results show that theoretical model fits the experimental results well and the corrosion mechanism can be modeled by a diffusion process accompanied with an irreversible chemical reaction when pH value of soak solution is no less than 3.5.

Atmospheric Corrosion of Steel A3 Deposited with Ammonium Sulfate and in the Presence of Sulfur Dioxide

A laboratory study of the atmospheric corrosion of carbon steel deposited with (NH4)2SO4 in the presence of SO2 is reported. The different levels of (NH4)2SO4 (0, 15, 30, 45, 60 μg·cm-2) were added on the surface of the samples before the exposure. The corrosion was investigated by a combination of gravimetry, Fourier transform infrared spectroscope and scanning electron microscopy. A detailed knowledge about the corrosion products was acquired, both quantitatively and qualitatively. The results show that the metal loss increased and the increasing tendency of corrosion rates slowed down with the increasing exposure time. The phase constituents of the corrosion products are mainly α-FeO(OH), γ-FeO(OH), and δ-FeO(OH).

Corrosion Caused by Sulfur Dioxide in Reinforced Concrete

The burning of fuel oil with high sulfur content in diverse industrial segments results in the generation of oxidized sulfur compounds (SOx). These emissions, directly or indirectly, lead to the deterioration of air quality with consequences including the development of lung diseases in the surrounding population, the generation of acid rain and damage to civil constructions, such as public buildings, public squares, historic monuments, bridges, etc. This article describes the mechanisms of corrosion that occur in reinforced concrete deterioration observed in an industrial plant by the action of direct emissions of sulfur dioxide. SO2 in this case study is from the burning of fuel oil high sulfur content from chimney of an industrial boiler. The deterioration of concrete was evaluated in the laboratory showing the formation of calcium sulfate and calcium sulfate hydrate associated with aluminum oxide (Al2O3) and calcium oxide (CaO).

Red tetrazolium as an effective inhibitor for the corrosion of cold rolled steel in 7.0 mol·L^(-1) H_2SO_4 solution

The corrosion inhibition of cold rolled steel(CRS) in 7.0 mol·L^(-1) H_2 SO_4 solution by red tetrazolium(RTZ) was carefully investigated using both experimental procedures and theoretical techniques. The results show that RTZ acts as an effective inhibitor for the corrosion of CRS in 7.0 mol·L^(-1) H_2SO_4, and the maximum inhibition efficiency is higher than 95% with a RTZ concentration of 2.0 mmol·L^(-1). The adsorption of RTZ on CRS surface follows Langmuir isotherm. RTZ effectively retards both cathodic and anodic reactions, and acts as a mixed-type inhibitor. EIS exhibits two capacitive loops, and their resistances increase drastically in the presence of RTZ. SEM and AFM confirm that the addition of RTZ could significantly retard the corrosion of CRS surface. A series of characterizations like FTIR, RS, XRD and XPS reveal that the corrosion CRS surface is composed of the corrosion products of iron sulfates, iron oxides and iron hydroxide, as well as inhibitor. Theoretical results of quantum chemical calculation and molecular dynamics(MD) indicate that the adsorption center of RTZ+(organic cationic part of RTZ) mainly relies on its tetrazole ring,and the adsorption of RTZ+on Fe(001) surface is in a nearly flat orientation mode.

CORROSION RESISTANCE OF HOT DIP GALVANIZED STEEL PRETREATED WITH BIS-FUNCTIONAL SILANES MODIFIED WITH NANOALUMINA

The corrosion behavior of hot dip galvanized steel pretrvated with bis-[triethoxysilylpropyl] tetrasulfide （BTESPT） modified with alumina particles was studied. The corrosion resistance of the passiving films was evaluated by Tafel polarization curve and electrochemical impedance spectroscopy. The films formed on the galvanized steel substrate were characterized by Fourier transform infrared spectroscopy and energy dispersive X-ray spectrometry. The surface morphology of the treated hot dip galvanized steel samples was observed by Field Emission Scanning Electron Microscope. The results show that the pretrvatments on the basis of silane films modified with nanoalumina particles have reduced both anodic and cathodic current densities, and increased total impedance in the measured frequency, consequently, improving corrosion protection for hot dip galvanized steel during immersion in NaCl solutions compared to chromate films and silane films.

Study on Corrosion Protection Method of Reinjection Water Treatment System in a Natural Gas Processing Plant

The research investigated the corrosion of the reinjection water system to ensure the safe production of the system.By analyzing the composition of the methanol-containing wastewater,the corrosion status of the injection water system was studied by the on-site materials 20#steel,Q235B steel and L316 steel for that the methanol-containing wastewater of a natural gas processing plant in northern Shaanxi had high acidity,Cl-and sulfide contents,salinity and corrosion.Then the grey system theory modeling software 3.0 was used to study the influence degree of various corrosion factors on the corrosion rate and depth of Q235B steel.The most important factors were determined,and countermeasures against corrosion were proposed.The results showed that L316 steel was more resistant to corrosion,and the corrosion rate was 0.0015 mm/a,which was less than the national standard(0.0760 mm/a).The maximum corrosion depth was 47.63μm,which was the lowest among the three materials.The corrosion rate and depth were the parent factors.Among the four factors of sulfide,Cl-,salinity and pH,grey relational degrees of sulfide were 0.75 and 0.80,respectively,which was the most important factor causing corrosion;using sulfur corrosion inhibitor protection method,TS-792C was selected by electrochemical method from three corrosion inhibitors.The impedance data simulation software ZSimpWin was used to simulate the equivalent circuit diagram,and the impedance of Q235B steel was the largest.The corrosion inhibition rate was up to 90.26%when corrosion rate was 0.0130 mm/a under the fitting of Tafel polarization curve,with the best anti-sulfur effect.At 80℃and a sulfide content of 300 mg/L,the corrosion rate of Q235B steel was less than 0.0760 mm/a.When the added amount was 100 mg/L,the corrosion current density and corrosion rate of the reinjection sewage was 0.462 mA/cm 2 and 0.0505 mm/a,both at the lowest values and with good temperature and sulfur resistance.

Corrosion of carbon steel,zinc and copper by air pollution in Chongqing

This paper presents the research on the atmospheric corrosion rates of carbon steel, zinc and copper in Chongqing, which was a corrosion subprogram of an international project, Regional Air Pollution in Developing Countries. We performed field exposure tests of carbon steel, zinc and copper at an urban site Guanyinqiao and a rural site Tieshanping inChongqing, then used grey relational analysis, based on the database of the whole corrosion project, to determine the order of the effect of environmental factors on corrosion rates of tested metals, and established dose-response functions for these three metals. The results showed that the two crucial agents of acidic environment, SO2 and H+, were common factors that contributed most to the corrosion of the tested metals. The established dose-response functions for outdoor carbon steel and zinc are proved applicable to use in Chongqing, but the function for copper needs further modifying. We employed these dose- response functions and general environmental data to elaborate the maps of corrosion rate respectively of carbon steel and zinc by geological information system (GIS) technique which help to identify areas of high corrosion damage risk. An acceptable annual average SO2 level of 21 μg/m3 for carbon steel and that of 61 μg/m3 for zinc are also put forward to control the air pollution impact on atmospheric corrosion in Chongqing urban areas.

Corrosion of Basic Refractories for Glass Tanks Using Petrol Coke and Countermeasures

Replacing heavy oil with petrol coke can greatly reduce the cost of glass production,but obviously shorten the service life of refractories used in the regenerator checker body of glass tanks.To prolong the service life of the regenerator checker body,the slag chemical composition and alkali-sulfur ratio of glass tanks after using petrol coke and the damage mechanism of the residual magnesia bricks in the regenerator checker body were studied,as well as the corrosion resistance of three magnesia based bricks(direct bonded magnesia chrome bricks,fused rebonded magnesia chrome bricks,and fused rebonded high-purity magnesium aluminate spinel bricks).On this basis,a series of targeted countermeasures were adopted to optimize the configuration of refractories,significantly improving the service life of checker bricks and meeting the requirements of glass industry development.

Investigation of Aloe lateritia Gel as Corrosion Inhibitor for Mild Steel in 2 M HNO3 and 1 M H2SO4 Media

Corrsion inhibition of Aloe lateritia gel for Mild steel in 2 M HNO3 and 1 M H2SO4 solutions was investigated by potentiodynamic polarization, Scanning electron microscopy (SEM) and Foutier transform infrared (FT-IR). Inhibition efficiency increased with the increase of the concentration of the gel. The optimal concentration of the gel gives maximum inhibition efficiency of 77.4% and 70.3% in 1 M H2SO4 and 2 M HNO3 respectively. Polarization plots shows that, the gel works as a mixed type inhibitor altering both cathodic and anodic reaction. SEM proves the uniform and pitting corrosion at the surface of Mild steel in 1 M H2SO4 and 2 M HNO3 respectively. Using FT-IR potential function groups from pure gel and some stretch shift was observed from corrosion product and some stretch shift from corrosion products was observed.

Hot Corrosion Behaviors of Ni-14%Cr Alloys in Molten Sulfate

The corrosion behaviors and mechanism of Ni-14%Cr alloys in molten salt with Na2SO4 at 1000℃ was investigated by means of XRD analysis and SEM observation. Results show that the alloys were subjected to the accelerated corrosion in molten salt and the corrosion kinetic of the alloy obeys the parabolic law. On the other hand, the corrosion-resistance of the alloy could be improved significantly by increasing of chromium content. Corrosion products may be divided into three layers, i. e. NiCr2O4, CoCr2O4, CoNi2S4, AlWO3 and Al2O3 granule are included in the outside of the scales, the continuous Al2O3 layer is localed in intermediate layer, and the sulfides is in the internal layer. The Cr2S3 phase in Ni-14Cr prevents the S and O from the matrix of the alloy. The morphology examinations tend to support the sulphidization-basic dissolution model previously proposed for hot corrosion mechanism.

Investigation of mortar corrosion by an acidophilic sulfur-oxidizing microorganism A.thiooxidans

The corrosion behavior of the acidophilic sulfur-oxidizing microorganism(ASOM)Acidithiobacillusthiooxidans(A.thiooxidans)on mortar was investigated for changes of medium and mortar,as well as for weight lossand surface morphology of mortar specimens.Weight loss analysis showed that mortar weight was reduced by(15.1±2.2)%after 56 d.Morphological surface analysis of mortar specimens showed weakly structured fibrous substances with2−100μm in size.The pH variations of the mortar surface and medium indicated that biogenic sulfuric acid had beenproduced by A.thiooxidans.The results prove that A.thiooxidans accelerated concrete corrosion and caused concretefailure.

Electrochemical behaviors of anode materials and their performance for bauxite desulfurization

Pyrite inside bauxite could be oxidized into soluble S-containing ions by electrolysis, and thus achieving bauxite desulfurization by using filtration. However, S-containing ions in electrolyte had some corrosion effects on electrode, especially for anode. In this work, six kinds of traditional materials were selected as anode, and their corrosion behaviors were examined by using electrochemistry characterization. Tafel and CV curves from simulating electrolyte suggested that their corrosion potentials were in the following order: Ni﹥C﹥SS﹥Fe﹥Cu﹥Pb–Ag. As expected, the desulfurization ratio and cell voltage from bauxite electrolysis were in the following order respectively: Cu﹥Ni﹥Fe﹥SS﹥C﹥Pb–Ag and Ni﹥Fe﹥SS﹥Cu﹥C﹥Pb–Ag. Finally, Ni was proposed a kind of excellent electrode material for bauxite desulfurization from electrolysis.

高含硫天然气净化装置腐蚀特征与典型腐蚀案例分析

相关高含硫天然气净化装置的工程建设、设备制造、材料选型等标准规范较少,多采用或借鉴石油炼制行业标准。普光气田天然气净化厂自2009年投产至今,因高酸性气体腐蚀,以及酸性气体、制造缺欠、材料缺陷等多因素耦合腐蚀,引发装置设备或设施多次泄漏,成为制约工厂安全、高效、长周期运行的主要问题。通过统计分析历年异常事件、设备检维修台账、压力容器管道检测台账等,归纳了高含硫净化装置重点腐蚀区域、影响因素、腐蚀机理,得出湿硫化氢腐蚀、高温硫腐蚀、二氧化硫腐蚀、垢下腐蚀为主要腐蚀形式;从区域、类别、诱因等不同角度归纳了腐蚀分布规律,脱硫、硫磺回收系统腐蚀占比达80%以上;重点剖析了基于硫化氢、液硫、制造缺欠等因素的典型腐蚀案例,提出了高含硫天然气净化装置腐蚀防控措施,为同类酸性气田装置、设备腐蚀监检测和防控提供了借鉴。

825合金在含单质硫高温高酸性环境中的局部腐蚀行为

在132℃、H_(2)S分压4.8MPa、CO_(2)分压1.6MPa、氯离子质量浓度42750mg·L^(-1)的气田模拟地层水中,通过腐蚀挂片试验研究了825合金在含单质硫(每升地层水中包裹合金的单质硫质量为10g)与不含单质硫条件下的局部腐蚀行为。结果表明:在不含单质硫条件下825合金几乎不发生腐蚀,腐蚀6d时的腐蚀速率仅为0.0077mm·a^(-1);添加单质硫腐蚀3d时腐蚀速率达到0.0552mm·a^(-1),合金发生了严重的局部腐蚀,随腐蚀时间的延长,合金表面局部腐蚀坑面积、腐蚀坑最大深度和腐蚀速率增大。在不含单质硫条件下合金表面腐蚀产物极少,主要为FeCO_(3),在含单质硫条件下,随着腐蚀时间的延长,表面腐蚀产物增多,主要为FeCO_(3)与FeS;单质硫在高温下发生歧化反应产生H^(+)和S^(2-),使825合金表面腐蚀产物膜破裂,从而加剧了局部腐蚀。

硫磺回收装置尾气焚烧炉异常分析与对策

某硫磺回收装置尾气焚烧流程出现尾气加热器泄漏、频繁熄炉及尾气管线积硫等问题,造成尾气硫排放超标。深入分析问题发生的原因,制定了一系列针对性措施:对尾气加热器泄漏问题,切换尾气处理部分跨线流程,建立尾气加氢系统氮气循环,同时升级材质;对频繁熄炉问题,控制尾气提标净化单元氧化反应器顶部含硫废气杂质含量;对尾气管线积硫问题,采取开工烟气线加盲板、尾气焚烧炉跨线增设氮气密封或停用、氧化反应器顶部废气水洗后排放等措施。尾气焚烧炉异常得到解决,其SO2排放浓度满足工艺加热炉大气污染物特别排放限值(不高于50 mg/m^(3))的要求。硫磺回收装置尾气焚烧炉实现长周期运行。

硫黄回收装置三级硫冷凝器泄漏原因分析与防护措施

硫黄回收装置的设备腐蚀问题是影响装置长周期安全运行的重要因素之一。多年来,装置三级硫冷凝器由于设备制造质量问题、汽包水质量差、装置负荷大幅波动及开停工期间腐蚀等多方面的原因,导致腐蚀泄漏频繁发生。近年来通过做好设备制造质量监控、严格控制炉水质量、做好工艺防腐、平稳生产、减少负荷大幅波动和开停工期间设备的保护等方面工作,三级硫冷凝器的腐蚀问题得到了充分解决。

硫酸介质中咪唑-4-甲基亚胺基硫脲对碳钢的缓蚀作用

目的碳钢因其优异的性能被广泛应用于工农业中,为解决碳钢在酸性介质中的腐蚀问题。方法以氨基硫脲和咪唑-4-甲醛为原料合成了Schiff碱化合物咪唑-4-甲基亚胺基硫脲(MIT),采用傅里叶红外光谱(FT-IR)、核磁共振谱(NMR)及质谱(EI-MS)表征了其分子结构。将MIT化合物作为H_(2)SO_(4)介质中碳钢的缓蚀剂,分别采用静态失重法、电化学测试及腐蚀形貌分析研究了其在0.5 mol/L H_(2)SO_(4)溶液中对碳钢的缓蚀性能,通过吸附模型、X-射线光电子能谱(XPS)等方法研究了MIT分子在碳钢表面的吸附行为,采用密度泛函理论(DFT)和分子动力学模拟(MD)方法进行了理论计算研究。结果MIT在H_(2)SO_(4)溶液中对碳钢的缓蚀效率随其添加量的增大而提高,随腐蚀环境温度的提高而下降,293 K下其在0.5 mol/L H_(2)SO_(4)溶液中的最佳质量浓度为240 mg/L,对应的缓蚀效率可达95.4%。MIT是一种混合型缓蚀剂,电化学缓蚀机理可解释为“几何覆盖效应”。在碳钢表面的MIT分子吸附属于化学和物理混合吸附(△G_(ads)^(°)=-31.62 kJ/mol,293K),且服从Langmuir吸附定律。结论MIT可有效抑制碳钢在H_(2)SO_(4)溶液中的腐蚀,MIT的合成既为H_(2)SO_(4)溶液中碳钢的腐蚀防护开发了一种有效方法,也为其他酸性介质中碳钢缓蚀剂的开发提供了新思路。

噻唑化合物对铜在硫酸中的缓蚀行为研究

利用失重法、极化曲线和电化学阻抗谱等方法研究2,5-二巯基-1,3,4-噻唑(DMTD)对纯铜在0.5 M的硫酸中的缓蚀作用。通过失重法研究缓蚀效果,并以其实验数据探讨吸附模型;采用极化曲线和电化学阻抗图谱研究缓蚀剂性能及机理。失重结果表明四种实验温度下DMTD均可明显减缓纯铜在硫酸溶液中的腐蚀,DMTD分子吸附满足Langmuir等温线;电化学分析可知DMTD抑制纯铜阴阳极腐蚀反应;随着DMTD浓度的增大,吸附膜层缓蚀性能增强;表面形貌观察分别证实了DMTD的缓蚀作用。2,5-二巯基-1,3,4-噻唑(DMTD)可有效抑制纯铜在0.5 mol·L^(-1)的硫酸中的腐蚀。

硫酸和柠檬酸溶液对水泥硬化浆体的腐蚀及机理

通过分析砂浆的外观、质量损失率和耐蚀系数,结合X射线衍射(XRD)、扫描电镜(SEM)和元素能谱分析(EDS)等微观测试手段,对比研究了硅酸盐水泥、铝酸盐水泥浆体在硫酸、柠檬酸溶液中的腐蚀规律与机理.结果表明:与硫酸溶液相比,柠檬酸溶液对两种水泥砂浆的腐蚀能力更强;与硅酸盐水泥相比,铝酸盐水泥表现出了较好的耐酸腐蚀性能,主要原因在于铝酸盐水泥硬化浆体中含有大量铝胶,在硫酸溶液中能够中和更多H+,在柠檬酸溶液中能够延缓H+向硬化浆体内部扩散的速率.