海水中硫酸盐还原菌作用下Q235钢表面腐蚀产物的形成和转化

用扫描电镜、电子探针、透射电镜及能谱仪等分析手段,研究了Q235钢在含有硫酸盐还原菌的海水中表面腐蚀产物的形成和转化。研究表明,硫酸盐还原菌首先在钢表面附着,随着细菌生命代谢活动的进行,最初的腐蚀产物由球形的（水合）氧化铁转化为海绵状的球形铁硫化物。腐蚀产物中存在FeS单晶。     

Mild steel corrosion modelling in presence of hydrogen sulphide in aqueous solutions

Abstract

Corrosion of mild steel in aqueous solutions containing hydrogen sulphide was modelled under the condition that an iron sulphide film was formed on the steel surface. In the present model, the iron sulphide forms on the steel surface as a result of a solid state reaction between iron and hydrogen sulphide which has several steps. First a very thin film of iron sulphide nucleates on the steel surface. Then, due to further growth of the initial thin layer, a more porous layer of iron sulphide forms on the initial film. In the present model, it is assumed that mass transfer through the thin iron sulphide layer (i.e. adjacent to the steel substrate) controls the corrosion rate of steel in H₂S aqueous solutions, and as a result electrochemical reactions were not considered. The model was verified against the published experimental data and effects of some parameters such as hydrogen sulphide partial pressure were investigated. The results show that increase in partial pressure of hydrogen sulphide leads to an increase in the corrosion rate of mild steel at the primary stages of the reaction, but as a consequence of formation of iron sulphide scales on the steel surface, it drops with respect to time.     

ASPS技术制备微纳结构FeS固体润滑渗硫层的研究

利用可移动活性屏低温离子渗流技术(简称ASPS技术),考察了工艺参数对渗硫层形貌、结构等的影响,制备了具有微纳结构的FeS固体润滑渗硫层。研究发现,渗硫温度比保温时间对FeS固体润滑渗硫层的形貌和组成结构影响更大。当渗硫温度230℃、保温2 h时,渗硫层以FeS为主,但含少量的FeS2,渗硫层中S/Fe原子摩尔百分比值接近1。渗硫层由微纳米量级的硫化物颗粒堆积而成,表层为富S层、次表层为FeS层,在渗硫层和基体之间存在厚度约400 nm的扩散层。     

Corrosion and deposition during the exposure of carbon steel to hydrogen sulphide-water solutions

Complex multi-phase corrosion films develop on rotating carbon steel discs exposed to aqueous hydrogen sulphide solutions; their structure and morphology can have a profound effect on the corrosion process. Iron sulphide corrosion products formed on corroding carbon steel discs in titanium autoclaves have been characterized after exposure periods ranging from 1 to 840 h at temperatures of 308, 373 and 433 K and a total initial pressure of 1.5 MPa. These reaction conditions pertain to the Girdler-Sulphide process for separating heavy water. In oxygen-free solutions, the evolution of corrosion products on the discs progresses from iron-rich to sulphur-rich phases according to the sequence, mackinawite (tetragonal FeS_1?x) → ferrous sulphide (cubic FeS) → troilite (hexagonal FeS) → pyrrhotite (hexagonal Fe_1?xS) → pyrite (cubic FeS₂), the latter phase being thermodynamically favoured. All phases except mackinawite appear as characteristic microcrystals of regular geometry, indicating relatively slow solution growth at low supersaturation. Higher temperatures accelerate the sequential transformations while higher speeds of rotation of the disc retard it. Edge turbulence induced at high rotation frequencies prevents the formation of solution-grown phases. Added oxidants promote the formation of the disulphide ion required for FeS₂ formation. Fe²⁺ ions released to the bulk solution by dissolution of the base metal and metastable sulphides are deposited as pyrrhotite or pyrite on the titanium vessel. The S₂^2? ion required for pyrite deposition is thought to arise by electro-oxidation of a sulphide species at the titanium surface.     

Corrosion behaviour of oil well casing steel in H2S saturated NACE solution

Abstract

The corrosion behaviour of oil well casing steel in H₂S saturated NACE solution (5 wt-%NaCl+0·5 wt-%CH₃COOH) was investigated by means of electrochemical methods, X-ray photoelectron spectroscopy and scanning electron microscopy. It was found that the investigated oil well casing steel can react with hydrogen sulphide in the H₂S saturated NACE solution at 25°C. During the reaction, corrosion films of mackinawite (FeS) form on the steel surface and the hydrogen atoms diffuse into steel matrix. The further corrosion of iron with H₂S can be retarded, and hydrogen permeation flux decreased, by the presence of the mackinawite film, which acts as a protective barrier provided it remains intact.     

Formation of poorly crystalline iron monosulfides: Surface redox reactions on high purity iron, spectroelectrochemical studies

In the use of iron for reductive dehalogenation of chlorinated solvents in ground water, due to presence of sulfate-reducing bacteria the formation of hydrogen sulfide is expected. To simulate those processes the interface between 99.99% pure iron and 0.1 M NaHCO₃ deoxygenated solution with 3.1 × 10⁻⁵-7.8 × 10⁻³ M Na₂S · 9H₂O added was studied. The surface processes were characterised by the in situ normal Raman spectroscopy (NRS) and ex situ techniques; X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive X-ray (EDX). The open circuit potential (OCP) was monitored during in situ NRS measurements, and potentiodynamic anodic polarization measurements were carried out to reveal electrochemical behaviour of iron electrode.Open circuit potential-time transients indicated that the native oxide is unstable in deaerated bicarbonate solution and undergoes reductive dissolution (i.e. autoreduction) leaving the metallic Fe covered by Fe(OH)₂, adsorbed OH⁻, and patches of ‘magnetite-like’ oxide. Immediately upon injection of the Na₂S-solution the iron interface undergoes complex redox surface processes and a poorly crystalline FeS film forms. Potentiodynamic anodic polarization measurements indicated a mechanical breakdown of the FeS film. The origin and initiation of this breakdown process is not clear but is probably a result of internal stress developed during film growth. Based on surface studies supported by electrochemical measurements, a conceptual model for the complex redox processes occurring at the iron interface is proposed. This model describes the structural development of a poorly crystalline FeS, which breaks down, allowing further dissolution of the Fe and formation of FeOOH at the interface. Simultaneously and despite the existence of thick layer of FeS the entrance of hydrogen was evident as the typical hydrogen cracks in bulk of the iron material. This work shed the light on the complexity of the iron/sulfide solution interface, this knowledge is important to understand the kinetic of reduction of organic groundwater contaminants.     

Tribology properties of composite layer of CrMoCu alloy cast iron by combined treatment of ion nitrocarburizing and sulphurizing

Composite layer with nitrocarbonide and sulfide was made on the surface of CrMoCu alloy cast iron by combined treatment of ion nitrocarburizing and sulphurizing. The composite layer is composed of sulfide layer, nitrocarbonide hypo-surface layer and its diffusing layer, the size of sulfide globular grains distributing equably on the surface is in nano-micron-scale, and the phase structure of the composite layer is composed of FeS, FeS1-x, Fe2C and Fe3N. Under oil lubrication, sulphurized surface shows good scuffing-resistance only under low velocity, and nitrocarburized and sulphurized surface greatly improves the scuffing-resistance and wear-resistance of CrMoCu alloy cast iron, its integrated friction and wear properties are better than those of the plain and sulphurized surfaces under all the velocities.     

A comparative pitting corrosion study of mild steel in different alkaline solutions containing salts with sulphur-containing anions

The localized corrosion of mild steel in alkaline solutions containing a salt with a sulphurcontaining anion (sodium sulphate, sodium sulphite, sodium thiosulphate, potassium thiocyanate and sodium sulphide) is studied by using potentiostatic and potentiodynamic techniques complemented with scanning electron microscopy.Alkaline solutions containing one of those salts produce pitting of mild steel at potential values more positive than those of the active-passive transition of iron in base. In the presence of either thiocyanate or thiosulphate anion iron pitting takes place through sulphide formation which reacts at the electrode surface yielding poorly protective ferrous sulphide. At potential more positive than the breakdown potential the kinetic behaviour fits a competitive surface reaction mechanism involving the formation of the passive film and the nucleation and growth of a ferrous sulphide salt layer. The proposed reaction model reproduces the corresponding experimental current-transients.     

The erosion-corrosion of carbon steel in aqueous H2S solutions up to 120°C and 1.6 MPa pressure

The erosion-corrosion of carbon steel in aqueous H₂S solutions at 120°C and 1.6 MPa has been studied by the rotating disc technique. Loss of iron from the carbon steel disc increases with the speed of rotation. However, the amount of iron sulphide adhering to the carbon steel (the scale) remains the same at different speeds of rotation, as a fresh layer of iron sulphide (mackinawite) replaces the dissolved one almost instantaneously. A preconditioned carbon steel disc with a pyrite surface, however, suffers no measurable metal loss or erosion-corrosion.Fluid velocity affects the nature of the film of iron sulphide formed on carbon steel surfaces exposed to H₂S solutions. Mackinawite is the predominant phase of the surface film formed at high fluid velocities but it transforms into pyrrhotite and pyrite at low velocities or in stagnant solution. Transformation of mackinawite to pyrrhotite and pyrite is accelerated in films under aqueous H₂S bubbles.     

The erosion-corrosion of carbon steel in aqueous H2S solutions up to 120°C and 1.6 MPa pressure

The erosion-corrosion of carbon steel in aqueous H₂S solutions at 120°C and 1.6 MPa has been studied by the rotating disc technique. Loss of iron from the carbon steel disc increases with the speed of rotation. However, the amount of iron sulphide adhering to the carbon steel (the scale) remains the same at different speeds of rotation, as a fresh layer of iron sulphide (mackinawite) replaces the dissolved one almost instantaneously. A preconditioned carbon steel disc with a pyrite surface, however, suffers no measurable metal loss or erosion-corrosion.Fluid velocity affects the nature of the film of iron sulphide formed on carbon steel surfaces exposed to H₂S solutions. Mackinawite is the predominant phase of the surface film formed at high fluid velocities but it transforms into pyrrhotite and pyrite at low velocities or in stagnant solution. Transformation of mackinawite to pyrrhotite and pyrite is accelerated in films under aqueous H₂S bubbles.     

Einflüsse von Silicium und Kohlenstoff auf die Sulfidierung von Eisen

Effects of silicon and of carbon on the sulfidation of iron The corrosive attack of steels by H₂S under FeS formation is impeding the use of heat exchangers in processes in which sulfidizing gases occur at low oxygen pressures – the project was aimed at finding ways and means to retard or suppress the FeS growth. Thermogravimetric investigations in H₂? H₂S at 400 °C showed that during the first 100 h of sulfidation a transition takes place from the linear kinetics controlled by the phase boundary reaction H₂S ? S (in FeS) + H₂ to the parabolic kinetics controlled by solid state diffusion in the corrosion products. During this transition the linear constant decreases with time and increasing sulfur activity a_s at the FeS surface (k₁ ? 1/a_s). Upon sulfidation of Fe-6%Si an internal Fe₃Si layer is formed te sulfidation is retarded since for long time ( 100 h) the slow surface reaction at high a_s is rate determining. Carbon deposits formed in carburizing atmospheres (a_c 1) on the iron surface, have a negligible effect on the sulfidation. Only graphitization of the iron surface at 700 °C after preceding carbon saturation at 1000 °C in CH₄? H₂ has an initially retarding effect. This study demonstrated possibilities of retarding the H₂S corrosion by Si or C which, however, are rather limited.     

铬钼铜合金铸铁表面渗硫工艺研究

利用低温离子渗硫技术，在铬钼铜合金铸铁材料表面制备硫化层，探讨了渗硫工艺参数对硫化层成分的影响规律，并确定了合理的渗硫工艺参数。由于硫化层只有在硬度较高的基体上才能发挥其润滑效果，故研究了材料表面预先氮化对渗硫的影响。结果表明预先氮化有利于硫化层的形成。     

恶臭腐蚀性硫化物的微生物治理研究

从土壤中分离筛选一株化能自养型的脱氮硫杆菌(Thiobacillus denitrificans,简称TD),经培养活化后用于抑制老化油储油罐污水及油田废水中微生物腐蚀及脱除硫化物。结果表明:加入TD生物制剂后,污水中FeS的去除率可达42.85%;污水中无机硫化物的总量去除率可达91.05%。介质中的SRB取片时比空白介质低2～3个数量级,菌量小于103 cells/ml;试验介质中无黑色的FeS出现,介质中也未检测到游离的硫离子存在;此外,TD生物制剂加入后基体材料N80钢表面腐蚀产物膜较少,可以看到样品表面保留了原有的痕迹,而添加无机培养基的油田废水以及空白油田废水中试样表面腐蚀产物膜较厚,且去除腐蚀产物膜后有明显的点蚀痕迹。TD生物制剂的加入抑制了基体材料表面SRB生物膜的形成,消耗了SRB代谢产生的活性FeS和H2S,从而抑制了由SRB引起的微生物腐蚀和环境污染。     

Roasting reaction of ferrous sulfide

The rate and mechanism of oxidation of ferrous sulfide have been studied by means of the spring balance and X-ray diffraction analysis over the temperature range from 500° to 700°C. The complete oxidation to oxides begins at 600°C. At the initial stage of oxidation, a slight increase of weight was found. It was observed by X-ray that the deficiency of iron ion in FeS occurs in this stage. This is interpreted as follows: iron ion reacts with oxygen by migrating from the interior of FeS crystal to the surface, without evolution of SO₂, until the deficiency of iron attains to a limiting value. Above 600°C the rate of oxidation does not change with temperature, so the rate-determining factor is diffusion of gas. Since the observed rate of oxidation depends upon the amount of the sample, the diffusion in the bed of the sample may determine the rate.     

Kinetic conditions for the simultaneous formation of oxide and sulphide in reactions of iron with gases containing sulphur and oxygen or their compounds

The scaling of pure iron has been investigated in N₂O₂SO₂ and COCO₂COS mixtures between 700 and 900°C. Simultaneous formation of FeO and FeS at the scale/gas phase boundary is observed when the diffusion in the aerodynamic boundary layer or the reaction at the scale/gas phase boundary is the rate-controlling step of the oxidation in O₂N₂ mixtures or of the sulphidation in COCOS mixtures. In those cases the addition of the second oxidant (SO₂ to O₂N₂ mixtures, and an increased CO₂ to COCO₂COS mixtures) increases the rate of the oxidation or sulphidation reactions. When, however, the diffusion of iron ions and electrons through the oxide or sulphide layer respectively, or the reaction at the metal/scale phase boundary are rate-determining, the thermodynamically stable phase (oxide or sulphide) is formed exclusively and the addition of the second oxidant has no influence on the scaling rate. These results may be understood from an evaluation of the equilibria prevailing at the scale/gas phase boundary.     

氧气浓度对铁的硫化物自燃性的影响

油品储罐中的H2S气体在没有O2存在的室温条件下能与储罐内壁铁的主要腐蚀产物Fe2O3发生化学反应生成铁的硫化物（以FeS为主）。铁的硫化物氧化放热是引起含硫油品储罐着火的主要原因。通过实验绘制出在不同起始氧气浓度下的Fe2O3的硫化产物氧化升温曲线和耗氧速度曲线，继而分析了氧气浓度对铁的硫化物自燃性的影响，氧气浓度越大，铁的硫化物自燃性越强。并且通过对耗氧速度的分析，可以了解铁的硫化物氧化反应速度的变化。     

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 文章利用中频感应炉炼制2种锰含量不同的硫化物自润滑合金，通过SEM观察断口并结合组织分析，研究合金中的硫化物形成以及合金的断裂行为。结果表明，硫化物处于韧性较差的珠光体中导致形成脆性解理断口，而硫化物处于韧性较好的铁素体中则形成韧性的韧窝断口。锰含量较低时硫化物以FeS为主，且为复相组织；含坚硬的V、Nb、Ti小颗粒化合物，易脱落；锰含量较高时硫化物以MnS为主。     

环烷酸和硫化腐蚀体系的热力学分析

从热力学角度讨论了环烷酸和硫化氢组成的腐蚀体系的热力学性质。结果表明：含高硫、高酸值的原油在温度小于３９８．９８Ｋ时,所形成的ＦｅＳ地环烷酸的侵蚀具有一定的保护作用,高于此温度将丧失保护作用,温度、浓度的变化不同程度的影响腐蚀产物的组成,讨论了ＦｅＳ在环烷酸中可能的溶解机理,探讨了选择成型缓蚀剂的原则。     

离子渗氮和离子渗硫复合处理表面的摩擦学性能

在４５钢离子渗氮表面,用低温郭了渗硫技术形成具有良好固体润滑作用的渗硫层。采用ＳＥＭ＋ＥＤＸ和ＸＲＤ研究了渗层的组织结构,采用销盘式磨损试验机在油润滑条件下,对原始、渗氮、渗硫以及渗氮渗硫复合处理表面进行了抗擦伤性能及耐磨性能的系统研究。并采用ＥＤＸ和ＡＥＳ分析了摩擦表面边界润滑膜的成分。结果表明：渗硫和渗氮处理均只能在低还条件下提高表面的抗擦伤性能。而复合处理能在各种速度条件下显著提高抗擦伤     

The Sulfidation Behavior of Several Commercial Ferritic and Austenitic Steels

The sulfidation behavior of C-steel, 1Cr-0,5Mosteel, 12Cr-1Mo-0.25V steel, 18Cr-10Ni-Ti steel, thebinary alloys Fe-20Cr, Fe-25Cr, Fe-30Cr, and pure Cr wasinvestigated between 400 and 700°C in a94Ar-5H₂-1H₂S gas mixture. All steels sulfidize according tocomplex kinetics which, after a period with decreasingrate, can be approximated by a linear rate law. Thescale of the three ferritic steels consists of two layers, an outer outward-growing one of FeSwith traces of dissolved Cr and an inner, inward-growingone, which contains in addition to Fe the alloyingelements Cr and Mn. Most of the outer FeS layer is separated from the inner layer and can be splitinto several partial layers, the number increasing withincreasing sulfidation time and temperature. The scaleon the austenitic 18Cr-10Ni-Ti steel differs insofar as that of the ferritic steels as theouter FeS layer contains some Ni and that a third layerof the spinel FeCr₂S₄ is formedbetween the outer and the inner layer. This intermediatelayer is responsible for the lower sulfidation rate of this materialcompared with that of the ferritic steels. The scale ofthe binary Fe-Cr alloys is similar to that of theaustenitic steel. From AE-measurements it can be deduced that the separation of the outer FeSlayer occurs during isothermal sulfidation and isaccompanied by an increase in the AE event rate. Theseparation is a consequence of the formation and growth of pores in the region close to the inner/outerlayer interface and the development of compressivegrowth stresses in the outer FeS layer. While detachmentof the FeS layer on the ferritic steels was already observed at 400°C, the austenitic steelshowed a similar separation of the FeS layer only at600°C. The detached FeS layer is obviously rathergas tight. Differences in the sulfur partial pressure ofthe bulk gas and the gas in the cavity between theinner and separated outer layer lead to a reduction ofFeS at the inner surface of the detached FeS layer. TheFe ions and electrons, produced by this reaction, diffuse outward, forming new FeS on the outerFeS surface. This process not only shifts the detachedFeS layer continuously away from the core of thespecimen but offers also the possibility of healing cracks in the separated FeS layer. This scaledetachment does not stop scale growth. After scaleseparation the total sulfidation reaction consists of atleast seven partial reactions: phase-boundary reaction at the outer surface, diffusion of iron ionsand electrons outwards in the detached FeS layer,formation of H₂S at the inner surface of thedetached layer, gas diffusion in the cavity, formationof FeS on top of the porous inner layer, gas diffusionin the channels of the porous inner layer, FeS formationat the metal/scale interface. When the new FeS layer ontop of the porous inner layer exceeds a critical thickness, the detachment of the FeSlayer from the inner porous layer repeats. This processcan take place several times, leading to an outer FeSpartial scale, split into several layers, which are separated by relatively large cavities andkept together only locally by FeS bridges. The overallreaction rate is controlled by the phase-boundaryreaction at the outermost FeS surface.