Environmental boundary and formation mechanism of different types of H_2S corrosion products on pipeline steel

To establish an adequate thermodynamic model for the mechanism of formation of hydrogen sulfide(H_2S) corrosion products,theoretical and experimental studies were combined in this work. The corrosion products of API X60 pipeline steel formed under different H_2S corrosion conditions were analyzed by scanning electron microscopy,energy-dispersive X-ray spectroscopy,and X-ray diffraction. A thermodynamic model was developed to clarify the environmental boundaries for the formation and transformation of different products. Presumably,a dividing line with a negative slope existed between mackinawite and pyrrhotite. Using experimental data presented in this study combined with previously published results,we validated the model to predict the formation of mackinawite and pyrrhotite on the basis of the laws of thermodynamics. The established relationship is expected to support the investigation of the H_2S corrosion mechanism in the oil and gas industry.     

大牛地奥陶系马五段硫化氢腐蚀机理与影响因素

为了解决大牛地气田硫化氢腐蚀严重问题,分析了硫化氢腐蚀机理以及影响腐蚀程度的因素。结合大牛地奥陶系马家沟组马五段地质条件以及硫化氢赋存条件确定该区域硫化氢形成的机理,为硫酸盐热化学还原反应;且该区域存在的大量石膏层为含硫化氢气体提供了良好的圈闭条件。硫化氢腐蚀模拟试验模拟了马五段地层水环境对N80钢和P110钢的腐蚀程度,P110钢的腐蚀程度较N80钢轻微,两者均属于极严重腐蚀。结合腐蚀表面微观形貌观测与腐蚀产物能谱分析得出:大牛地奥陶系马家沟组马五段硫化氢腐蚀机理为高温高压下CO2/H2S电化学腐蚀为主;并伴随有高Cl-破坏腐蚀产物膜加速腐蚀。硫化氢腐蚀影响因素分析得出温度和CO2含量增加会加速硫化氢腐蚀。     

X65MS钢在饱和H2S/CO2环境下的腐蚀产物研究

利用高温高压反应釜模拟酸性油气输送环境,研究X65MS管线钢在饱和H₂S/CO₂环境下的腐蚀行为.采用加速腐蚀实验法评测不同浸泡周期下的平均腐蚀速率.借助X射线衍射(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)和电子探针(EPMA)等测试技术,分析了不同实验周期下氧化产物膜层的物相组成、表面形貌和截面形貌.结果表明,根据平均腐蚀速率随时间变化曲线的走势与氧化膜层的结构特征,腐蚀过程分为三个阶段.腐蚀过程以H₂S腐蚀为主,氧化产物主要为硫铁化合物(Fe_○xS_○y).随着浸泡时间的增加,铁元素比例减小,富S相比例增大,腐蚀产物膜层厚度增加,结构由疏松逐渐变为均匀、致密,腐蚀产物顺序为马基诺矿(Mackinawite)→过渡相陨硫铁(Troilite)→磁黄铁矿(Pyrrhotite),稳定的磁黄铁矿对X65MS管线钢基体的耐蚀性起到保护作用.     

Effects of silty sand on CO<Subscript>2</Subscript> corrosion behavior of low-Cr tubing steel

An experimental study was carried out to assess the effects of silty sand on the CO 2 corrosion behavior of 1 wt% Cr (1Cr) and 3 wt% Cr (3Cr) tubing steel under 0.5 MPa CO 2 at 100°C and 1.5 m/s flow velocity.The 1Cr and 3Cr specimens both suffered general corrosion,but the surface was coarser in the pure CO 2 corrosion environment.Under silty sand conditions,severe pitting corrosion occurred on the 1Cr specimens and some acicular pitting appeared on the 3Cr specimens.The average corrosion rates of 1Cr and 3Cr steels increased by factors of 3 and 1.6,respectively.The corrosion products were analyzed by scanning electron microscopy (SEM),energy dispersive spectroscopy (EDS),X-ray diffraction (XRD),and electrical impedance spectroscopy (EIS).The results show that silty sand acts as an inclusion in corrosion product films and reduces the homogeneity and density of the products,rather than abrading the corrosion film.Ion-diffusion channels may build up around the irregular silty sand;this would degrade the protective capabilities of the product films and aggravate corrosion.     

硫化氢质量浓度和温度对碳钢在NACE溶液中腐蚀行为的影响

采用动电位极化曲线和电化学阻抗谱等电化学实验方法以及扫描电镜和能谱等表面分析技术对20#碳钢在不同H2S质量浓度(0,95.61,103.22,224.16 mg.L-1)、不同温度(25,35,45℃)下的NACE溶液(含CO2)中腐蚀行为进行了研究,同时对该环境下腐蚀产物的形成机制进行了探讨.发现在含有CO2的NACE溶液中,加入少量H2S,能加剧碳钢腐蚀,加速阳极铁的溶解和阴极氢气的析出.随着H2S质量浓度的增加,腐蚀电流密度增大,碳钢腐蚀加剧.温度升高,腐蚀极化电阻变小,腐蚀也会加剧.腐蚀试样外层絮状腐蚀产物主要是铁碳化物,接近基体表面的腐蚀产物主要是铁硫化物.     

Effect of Al2O3 and Y2O3 on the corrosion behavior of ZrO2-benzotriazole nanostructured coatings applied on AA2024 via a sol-gel method

zirconia-based nanostructured coatings were deposited on AA2024 to improve the corrosion resistance properties. Three different nanostructured coatings, namely, zirconia-benzotriazole, zirconia-alumina-benzotriazole, and zirconia-yttria-benzotriazole, were applied on AA2024 via a sol-gel method using the dip-coating technique. Next, the coatings were annealed at 150℃ after each dipping period. The phases and morphologies of the coatings were investigated using grazing incidence X-ray diffraction (GIXRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), and atomic force microscopy (AFM). The corrosion properties were evaluated using electrochemical methods, including polarization and electrochemical impedance techniques in 3.5wt% NaCl solution. The obtained results confirm the formation of homogeneous and crack free zirconia-benzotriazole-based nanostructured coatings. The average roughness values for zirconia-benzotriazole, zirconia-alumina-benzotriazole, and zirconia-yttria-benzotriazole nanostructured coatings were 30, 8, and 6 nm, respectively. The presence of alumina as a stabilizer on zirconia coating was found to have a beneficial impact on the stability of the corrosion resistance for different immersion times. In fact, the addition of alumina resulted in the dominance of the healing behavior in competition with the corrosion process of zirconia-benzotriazole nanostructured coating.     

硫酸盐还原菌的腐蚀机理

采用硫酸盐还原菌 ( SRB)培养技术 ,研究了 SRB的生长特性 ,结果表明 :在 SRB的整个生长过程中 ,培养液中 SO2 -4 浓度逐渐减小 ;但当 SRB处于繁殖期时 ,H2 S释放量逐渐增大 ;处于衰亡期时 ,H2 S释放量逐渐减小。同时 ,对三种油田管材进行浸泡试验 ,采用扫描电镜对试样腐蚀产物形貌及组成进行分析 ,发现腐蚀产物主要为 Fe S和 Fe1-x S。着重研究了 SRB的腐蚀机理 ,结果表明 :SRB的代谢产物 ,特别是 H2 S,是加快腐蚀的主要原因 ,它们对腐蚀反应即有阴极去极化作用 ,又有阳极去极化作用。     

Investigation of the deterioration of passive films in H<Subscript>2</Subscript>S-containing solutions

The effect of H₂S on the corrosion behavior of 316L stainless steel was investigated using electrochemical methods by changing the gas condition from CO₂ to H₂S and then back to CO₂. The presence of H₂S showed an acceleration effect on the corrosion of 316L stainless steel in comparison with CO₂. The acceleration effect remained even after the complete removal of H₂S by CO₂, indicating that the passive film was irreversibly damaged. X-ray photoelectron spectroscopy (XPS) analysis indicated that the passive film was composed of Cr₂O₃, Fe₂O₃, and FeS₂ after being immersed in H₂S-containing solutions. The semiconducting property of the passive film was then investigated by using the Mott-Schottky approach. The presence of sulfides resulted in higher acceptor and donor densities and thus was responsible for the deterioration of passive films.     

Intense laser induced field ionization of C<Subscript>2</Subscript>H<Subscript>2</Subscript>, C<Subscript>2</Subscript>H<Subscript>4</Subscript>, and C<Subscript>2</Subscript>H<Subscript>6</Subscript>

Using HOMO Field Ionization Model, the tunneling probabilities and the theoretical threshold intensities of the field ionizations of acetylene, ethylene, and ethane in intense laser field are calculated. C2H2, C2H4, and C2H6 were irradiated by 800 nm, 100 fs laser pulses with the intensity range of 10^13-10^14 W/cm^2. A TOF-mass spectrometer was coupled to the laser system and used to experimentally investigate the field ionization of these molecules. The experimental ionization threshold intensities are obtained. The calculating results of the three molecules agree well with the experimental results, indicating that HOMO Field Ionization Model is valid for the ionization of polyatomic molecules in intense laser field.     

海砂型氯离子与水泥胶体的结合和机理

为了研究海砂中氯离子对钢筋混凝土结构耐久性影响,分析氯离子对结构中钢筋的腐蚀作用,将海砂引入氯离子的形式从传统的内掺型中剥离出来,采用NaCl溶液浸泡河砂模拟海砂,研究氯离子与水泥胶体的结合机理,并结合SEM微观实验和EDS的元素扫描结果,对氯离子在砂子周围的发布、结合规律作了描述.实验表明:水泥稳定后与氯离子的结合率在60%左右,海砂型与内掺型氯离子结合、传播方式有所不同,海砂型引入的氯离子存在一个从海砂表面到水泥凝胶内部的渗透过程,在此基础上提出海砂型氯盐侵蚀的概念,基于微观试验结果讨论了其结合和传播机理.     

Effect of NaNO<Subscript>3</Subscript> concentration on anodic electrochemical behavior on the Sb surface in NaOH solution

The effect of NaNO₃ concentration on the anodic electrochemical behavior of antimony in 4 M NaOH solution was investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analyses. The mechanism of NO₃- concentration effect on the anodic electrochemical behavior of antimony was proposed, and its availability was confirmed by experimental results. The effect of NaNO₃ on the anodic behavior of antimony in NaOH solution can be interpreted as a stepwise formation of different antimony compounds with different NaNO₃ concentrations. Metallic antimony is apt to be oxidized into Sb₂O₃ within the NaNO₃ concentration range of 0-0.48 M. NaSbO₃ can be found on the antimony surface when the NaNO₃ concentration increases gradually. Insoluable NaSbO₃ inhibits the anodic oxidation of antimony due to its shielding effect on the mass transport of the reactants and products. Surface morphology and composition were analyzed by X-ray photoelectron spectroscopy (XPS), scanning electronic microscopy (SEM), and electron dispersion spectroscopy (EDS) analyses. Results indicate that the anodic oxidation layer is composed of Sb₂O₃, NaSbO₃, and Sb. The atomic proportion of antimony in the form of NaSbO₃ increases with increasing NaNO₃ concentration due to the powerful oxidizing property of NaNO₃.     

Microstructure and corrosion behavior of Al<Subscript>3</Subscript>Ti/ADC12 composite modified with Sr

In this study, we investigated the effect of the addition of Sr (0wt%, 0.1wt%, 0.2wt%, and 0.3wt%) on the microstructure and corrosion behavior of Al₃Ti/ADC12 composite by optical microscopy, X-ray diffraction, scanning electron microscopy, and energy diffraction spectroscopy. The results reveal that the α-Al phases were nearly spherical and 40 μm in size and that the eutectic Si phases became round in the composite when the Sr content reached 0.2wt%. The Al₃Ti particles were distributed uniformly at the grain boundary. The results of the corrosion examination reveal that the Al₃Ti/ADC12 composite exhibited a minimum corrosion rate of 0.081 g·m–2·h–1 for an Sr content of 0.2wt%, which is two thirds of that of unmodified composite (0.134 g·m–2·h–1). This improved corrosion resistance was due to galvanic corrosion, which resulted from the low area ratio of the cathode to anode regions. This caused a low-density corrosion current in the composite, thereby yielding optimum corrosion resistance.     

塔河油田某侧钻深井油管断裂失效原因

 塔河油田某稠油区高含CO₂及H₂S,某侧钻井在井下P110S 油管发生典型的断裂失效。为查明油管断裂原因,结合油管服役的井下工况条件,对断裂油管的化学成分、力学性能、金相组织、微观形貌进行测试及分析,对油管断裂部位的腐蚀产物进行了能谱分析。通过对断裂油管进行详细观测及试验分析,认为腐蚀是导致该井油管断裂的主要原因。通过对该侧钻井油管二种典型腐蚀特征的分析可知油管内壁以点状腐蚀为主,腐蚀机理为典型的CO₂电化学腐蚀;外壁主要为一侧分布的沟槽状腐蚀及坑蚀,腐蚀机理为低pH 值酸液条件下的电化学腐蚀及缝隙腐蚀。针对上述典型腐蚀问题,提出了针对性预防油管腐蚀穿孔的措施。     

Shape evolution of antimony oxychloride from sheaf-like to quasi-wafer structures

Antimony oxychloride Sb8O11Cl2(H2O)6 products with various morphologies including sheaf-like,rhombic-plate,oval leaf-like and quasi-wafer have been successfully synthesized via a mild and facile solution route at room temperature.The morphologies and structures of the as-prepared samples were characterized by X-ray powder diffraction(XRD),scanning electron microscopy(SEM) and transmission electron microscopy(TEM).A possible formation mechanism of these structures is proposed according to the experimental results and analysis.     

Bio-oxidation of pyrite, chalcopyrite and pyrrhotite by Acidithiobacillus ferrooxidans

This paper deals with the bio-oxidation processes by Acidithiobacillus ferrooxidans of pyrite, chalcopyrite and pyrrhotite. Our experimental results show distinctive bio-oxidation characteristics for the three sulfide minerals. In the presence of A. ferrooxidans, the sulfide oxidation rates generally decrease in the order of pyrrhotite, chalcopyrite and pyrite. The pH during bio-oxidation of pyrite tends to decrease as a whole, whereas a rise-fall pattern was recorded for both chalcopyrite and pyrrhotite in their pH variations. No deposition was observed during the bio-oxidation of pyrite, suggesting a possible link to lower pH value in the process. However, large amounts of jarosite and element sulfur were determined in the bio-oxidation processes of chalcopyrite and pyrrhotite. A. ferrooxidans individuals were found directly as attachments to erosion pits on the smooth surface of pyrite. The erosion pits are similar to the bacterium in shape and length, and thus are probably products of dissolution of organic acid secreted by the cells on the mineral surface. More complicatedly, biofilm exists on the surfaces of chalcopyrite and pyrrhotite. This type of structured community of A. ferrooxidans is enclosed in the extracellular polymeric substances (EPS), and covered with the deposition generated in the bio-oxidation processes of chalcopyrite and pyrrhotite. Different bio-oxidation processes of pyrite, chalcopyrite and pyrrhotite may be linked mainly to characteristics of individual minerals and the pH in the reaction solution of the bio-oxidation system.     

Influence of chromium on the initial corrosion behavior of low alloy steels in the CO2-O2-H2S-SO2 wet-dry corrosion environment of cargo oil tankers

The influence of Cr on the initial corrosion behavior of low-alloy steels exposed to a CO2–O2–H2S–SO2wet–dry corrosion envi-ronment was investigated using weight-loss measurements, scanning electron microscopy, N2 adsorption tests, X-ray diffraction analysis, and electrochemical impedance spectroscopy. The results show that the corrosion rate increases with increasing Cr content in samples subjected to corrosion for 21 d. However, the rust grain size decreases, its specific surface area increases, and it becomes more compact and denser with increasing Cr content, which indicates the enhanced protectivity of the rust. The results of charge transfer resistance (Rct) calculations indicate that higher Cr contents can accelerate the corrosion during the first 7 d and promote the formation of the enhanced protective inner rust after 14 d; the formed protective inner rust is responsible for the greater corrosion resistance during long-term exposure.     

Study on reduction of MoS<Subscript>2</Subscript> powders with activated carbon to produce Mo<Subscript>2</Subscript>C under vacuum conditions

A method of preparing Mo₂C via vacuum carbothermic reduction of MoS₂ in the temperature range of 1350-1550℃ was proposed. The effects of MoS₂-to-C molar ratio (α, α=1:1, 1:1.5, and 1:2.5) and reaction temperature (1350 to 1550℃) on the reaction were studied in detail. The phase transition, morphological evolution, and residual sulfur content of the products were analyzed by X-ray diffraction, field-emission scanning electron microscopy, and carbon-sulfur analysis, respectively. The results showed that the complete decomposition of MoS₂ under vacuum is difficult, whereas activated carbon can react with MoS₂ under vacuum to generate Mo₂C. Meanwhile, higher temperatures and the addition of more carbon accelerated the rate of carbothermic reduction reaction and further decreased the residual sulfur content. From the experimental results, the optimum molar ratio α was concluded to be 1:1.5.     

Improved hydrogen desorption properties of Co-doped Li<Subscript>2</Subscript>BNH<Subscript>6</Subscript>

The hydrogen desorption properties of Li 2 BNH 6 were improved by doping with cobalt. With the addition of CoCl 2 (7 wt%), more than 8 wt% of hydrogen was released from Li 2 BNH 6 at temperatures below 210°C, which is approximately 90°C lower than that of pristine Li 2 BNH 6 . X-ray diffraction, Fourier transform-infrared and Raman characterizations revealed that the dehydrogenation was a stepwise process with the formation of intermediates Li 4 BN 3 H 10 and LiBH 4 and final products of Li 3 BN 2 and LiH. The introduction of Co greatly accelerated the dehydrogenation of Li 4 BN 3 H 10 . X-ray absorption near-edge structure measurements revealed that Co and CoB species formed during ball milling of CoCl 2 with LiBH 4 and LiNH 2 , which may function as catalyst in the subsequent dehydrogenation.     

铁基金属玻璃涂层在无铅钎料中的耐腐蚀性及机理

选用Fe基非晶合金粉末(含有Cr、Mo、Ni、P、B、Si),采用等离子喷涂方法在Q235基体上制备了金属玻璃涂层.在自行设计的腐蚀实验装置中将Q235钢、1Cr18Ni9Ti不锈钢和覆有Fe基金属玻璃涂层的Q235钢浸入450,℃的高温液态无铅钎料Sn-3.5,Ag-0.5,Cu中进行腐蚀,利用扫描电子显微镜微观分析了腐蚀后的微观形貌及腐蚀产物.研究结果表明:相同实验条件下,Q235钢和1Cr18Ni9Ti不锈钢表面均腐蚀严重,断面微观组织分为钎料层、腐蚀层和基体层.其中Q235钢的腐蚀剧烈,腐蚀层成分为FeSn2;1Cr18Ni9Ti不锈钢腐蚀较严重,腐蚀层成分为(Fe,Cr)Sn2.Q235基体表面的Fe基金属玻璃涂层腐蚀前后断面微观形貌变化不大,没有出现明显的腐蚀分层,表现出了非常好的耐高温无铅钎料腐蚀的能力.     

Synthesis and characterization of high density and high aspect ratio Ag<Subscript>2</Subscript>S nanoparticle nanowires from a paired cell method

Ag₂S nanoparticle nanowires were prepared in a porous anodic aluminum oxide template by a simple paired cell method,and were characterized by XRD,FESEM,HRTEM and EDS.The results showed that the as-prepared nanowires were composed of monoclinic Ag₂S nanoparticles.The nanowire diameters ranged from 165 to 270 nm,and Ag₂S nanoparticles were nearly spherical with diameters of 40 to 60 nm.The paired cell method is simple,low cost and easy to control for the fabrication of high density and high aspect ratio Ag₂S nanoparticle nanowires.A formation mechanism for the nanoparticle nanowires was suggested.