Erosion‐corrosion of Q235 and 5Cr1/2Mo steels in oil with naphthenic acid and/or sulfur compound at high temperature

The erosion‐corrosion behaviors of Q235 steel and 5Cr1/2Mo steel in oil with naphthenic acid and/or sulfur compound at high temperature were studied in a hot oil loop simulating oil refining environments. The effects of impinging flow rate, incidence angle, and total acid number (TAN), and sulfur content on erosion‐corrosion behavior were assessed. The eroded surfaces were characterized by scanning electron microscopy (SEM) and XPS. The results showed that both corrosion resistance and hardness of steels play an important role in combating erosion‐corrosion. Sulfide films formed on the surface were significant in understanding the erosion‐corrosion behavior when both naphthenic acid and sulfur compound were present. Erosion‐corrosion regimes were determined on the basis of mechanism analysis of the damage process.     

用于工业系统腐蚀微生物的杀菌剂研究进展

工业水环境中微生物引起的腐蚀一直是造成工程材料失效的重要原因之一,杀菌剂作为一种简单高效的杀灭微生物的方法,在工业微生物腐蚀防控领域中发挥着重要作用.针对近年来硫酸盐还原菌和藻类引起的管线钢微生物腐蚀行为以及霉菌引起的铝合金材料的腐蚀行为,结合相应工业系统杀菌剂的研究和应用情况,综述了用于防控微生物腐蚀的多种杀菌剂的应用优势及其研究进展,总结了杀菌剂在工业系统应用所面临的问题和未来发展趋势.其中,季铵盐和季鏻盐作为油田系统中常用的阳离子杀菌剂,能够在低浓度下有效杀灭硫酸盐还原菌,并抑制微生物腐蚀.胍盐类杀菌剂以其稳定性和广谱性在工业系统中应用广泛.杂环类杀菌剂种类繁多,部分杂环类杀菌剂不仅具有抗细菌和真菌的效果,还具有一定的缓蚀作用.有机溴类物质则是一种逐步兴起的污水处理杀菌剂.此外,多种杀菌剂的复配使用也是一种经济有效的提升杀菌效果的方法.目前,通过改性、合成等方法将尽可能多的抗菌基团集中到一种杀菌剂或某种基底材料上,逐渐成为开发新型抗菌物质的趋势.     

Corrosion control of phenylthiourea polymers on aluminium in alkaline medium

Simple phenylthiourea compounds are known for their high solubility in alkaline medium and for good corrosion control. The monomer N‐(4‐hydroxy‐3‐methoxybenzal)‐N′‐(4′‐hydroxyphenyl) thiourea was condensed with pimeloylchloride and azeloylchloride through inter‐facial polycondensation method to synthesize the polymers. The polymers were dissolved in 2 N sodium hydroxide and their corrosion controlling efficiency on aluminium was studied through AC impedance and potentiodynamic polarization methods.     

交流电频率对X80管线钢在酸性土壤模拟溶液中腐蚀行为的影响

通过电化学测试、浸泡实验和表面分析技术研究了交流电频率(50~400 Hz)对X80钢在鹰潭酸性土壤模拟溶液中腐蚀行为的影响。结果表明,随交流电频率的增加,X80钢的腐蚀速率逐渐减小,腐蚀程度减弱。交流电作用下X80钢生成的腐蚀产物疏松、裂纹多,对基体的保护性很差。X80钢的腐蚀电位偏移量随交流电频率的增大而减小。随交流电频率的增大,阴、阳极极化曲线的振荡幅度逐渐减弱。交流电的施加不仅使阴、阳极的电流密度增大,还使阴极反应由混合控制逐渐向活化控制转变。     

Effect of the molecular structure of some quinones on their corrosion inhibiting action

The molecular characteristics obtained by quantum chemical self‐consistent field (SCF) calculations of a series of quinones are correlated with the experimentally determined inhibitor efficiency for mild steel corrosion in neutral aqueous medium. It was established that the decrease of the ionization potential and the increase of the dipole moment of the quinone molecules favor the higher protective effect. The electron density and the geometric molecular structure have also been computed and are discussed in view of the corrosion inhibition.     

Corrosion characteristics of electroless Ni–P coating in sulfur‐bearing solution

The corrosion behaviors of electroless Ni–P coatings deposited on carbon steel in sulfur‐bearing solutions were investigated by weight gain test and scanning electron microscopy. The results indicate that the corrosion rate of electroless Ni–P coating was directly related to the sulfur content, immersion time, and test temperature. The corrosion rate increased with the prolonged immersion time. Increasing the temperature can markedly increase the corrosion rate of electroless Ni–P coating. The electroless Ni–P coating had a better corrosion resistance than 316L stainless steel against Cl^? corrosion in sulfur‐bearing solution.     

Relationships governing slip in the structure of the weld metal of welded joints in heat-resisting pearlitic steels

Summary

Previous papers have shown the high‐current AC‐MIG welding process to be superior to the conventional DC‐MIG process in terms of welding efficiency and welded joint performance. The authors have used the AC‐MIG process to weld heavy‐gauge steel plates at a tensile strength level of 980 MPa. Weld metal with a very low hydrogen content is obtained by the newly developed process, resulting in a reduced preheating temperature during welding of high‐strength steels. The AC‐MIG process also produces an arc climbing effect with electrode negative polarity ‐ a desirable effect in narrow‐gap welding. AC‐MIG weld metal further contains low oxygen, conferring high toughness. As a result, a narrow‐gap AC‐MIG welding process has been developed to ensure high efficiency in processing and metallurgically high‐quality welds in welding of 980 MPa high‐strength steels for penstocks (pressure shafts) in hydroelectric power stations. Welding wires with chemical compositions satisfying suitable strength and toughness criteria have been trial‐manufactured. Suitable welding parameters have also been determined for narrow‐gap welding of penstocks.     

Assessment and control of MIC in a sugar cane factory

Microbiologically influenced corrosion (MIC) in a sugar cane factory was studied. Also, two types of industrially recommended biocides and a mixture of them were evaluated by using kill time method. The results showed that some countermeasures were necessary to be applied to lower the risk of MIC. The concentrations of the biocides used in this study revealed that the biocides, under the testing conditions, had no biocidal effect what so ever.     

乙烯裂解装置炉管焊缝腐蚀失效分析

针对发生失效的乙烯裂解装置炉管焊缝,采用材料化学成分分析、宏观形貌观察、金相检查、扫描电镜和能谱分析等手段进行了失效分析,同时测量了原料油的终馏点,模拟了含焊接缺陷的炉管内的流场。结果表明:焊缝腐蚀区存在大量硫及低熔点共晶物;失效炉管段的介质温度处于加氢尾油的终馏点附近;活性硫在镍基焊缝偏聚,镍与硫形成的低熔点共晶物在高温下熔化,并被介质冲走,导致炉管快速腐蚀。     

Mikrobiell induzierte Korrosion (MIC) in marinem Milieu

Microbial induced corrosion (MIC) in marine environment Steel box‐piles immersed in brackish water of the Baltic Sea show a perforation of the wall (10 mm of thickness) after a service life of 35 years. The calculated corrosion rate by that is 290 μm/a and is much higher than usual corrosion rates in marine environments. Investigations of material have shown, that the steel corresponds well with a common mild steel used for sheet piles. At the outer plain the structure shows normal surface corrosion, while inside, according to microscopic studies, pitting corrosion occurs. Beneath the oxidative corrosion product (e.g. γ‐Fe₂O₃, maghemite) there are sulfur enriched phases as well as elementary sulfur detectable (by means of different methods like X‐ray Diffraction, REM‐EDX and IR‐Spectroscopy). The corrosion products are covered with a calcitic layer and have to be removed prior to investigation. By means of microbiological techniques, “sulfate reducing bacteria” (SRB) could be detected in high concentrations between the corrosion products inside the steel structures. These bacteria are deriving from the marine sediment and earn their energy using electrons from the steel accompanied by chemical reduction of the sulfate from the sea water. By that the anodic process of iron dissolution is accelerated. The anaerobic environment inside the closed structures promotes the metabolic activity of the bacteria. As a first and cost saving repair it is proposed, to force the oxidation by opening the structures. Of course preventative corrosion protection – coating (inside and outside) or filling (inside) – would have been the best prevention of corrosion.     

An ultra‐sulfur Hastelloy alloy C‐4

The effect of sulfur on solidification‐segregation and corrosion resistant properties of Hastelloy C‐4 corrosion‐resistant alloy was studied. It was found that strict controlling the content of sulfur can reduce the width and temperature interval of the solid‐liquid biphase region and the segregation degree of the alloy, resulting in a higher corrosion resistance. An improved low segregation Hastelloy C‐4 corrosion resistant alloy was developed.     

Corrosion performance of Zn–Mg–Al coated steel in accelerated corrosion tests used in the automotive industry and field exposures

The corrosion performance of Zn–Mg(1–2%)–Al(1–2%) (ZMA) coatings has been compared to zinc–iron alloy (galvannealed, GA) and zinc–aluminum coating (Zn–5Al, Galfan) as well as to conventional zinc coatings produced by hot‐dip galvanization (HDG) and electrogalvanization (EG). For this purpose, cosmetic samples (painted and uncoated) and hem‐flange panels were produced. Their corrosion performance was compared in three different accelerated corrosion tests, as regularly used by the automotive industry, e.g., VDA621‐415, N‐VDA (VDA233‐102), and Volvo STD 423‐0014. As can be concluded from our results, the behavior of ZMA coatings was strongly dependent on the testing conditions as well as on the configuration of the samples. The advantageous effect of ZMA coating was more pronounced in open situations than in confined ones, irrespective of the testing conditions. ZMA coatings provided a significant improvement in comparison to conventional coatings in tests involving a significant salt load such as VDA621‐415 or neutral salt spray especially on cosmetic configurations. By contrast, the beneficial effect of ZMA coatings was less obvious in tests with lower salt load (VDA233‐102, Volvo STD423‐0014), particularly when considering cosmetic corrosion on painted samples and corrosion in confinement. Interestingly, no significant differences were observed between samples with varying Al and Mg content in the metallic coating (1–2% each). The results were compared to data from field exposure at stationary sites.     

杀生剂对凝汽器不锈钢管耐蚀性能的影响

用点蚀电位法和失重法评价了四种杀生剂在不同冷却水中对凝汽器用TP304不锈钢管耐蚀性能的影响,并对线性极化法作了说明。杀生剂a、b和c对不锈钢有腐蚀促进作用,腐蚀促进作用依次为杀生剂c>杀生剂b>杀生剂a,杀生剂d有缓蚀作用。用腐蚀失重法评价杀生剂对冷却水中的不锈钢耐蚀性能的影响,既不合理,也很难测准。点蚀电位法是一种较好的方法,但也要选择合适的空白水样。     

硫磺再生塔内件腐蚀失效分析

目的查明硫磺再生塔内件腐蚀失效的原因,提出避免该内件再次失效的对策。方法采用目测、金相显微镜和电子显微镜以及能谱分析等手段,分析内件腐蚀失效的原因。结果能谱分析表明,该内件基体镍含量偏低,腐蚀产物中硫含量较高。目测可见内件断口表面粗糙,电子显微镜形貌与金相显微分析表明,在晶界处有大量颗粒状碳化物析出。结论导致该内件失效的原因主要是热处理不当,造成了晶间碳化物的析出,从而导致了晶间腐蚀的发生。同时镍含量偏低也降低了材料的耐蚀性,含硫腐蚀性介质的冲刷作用也加重了低耐蚀性内件的晶间腐蚀。应使用化学成分符合国标304不锈钢材料生产的内件,同时要避免内件在生产与使用过程中因热处理不当造成晶间碳化物的析出。     

埋地金属管道交流电腐蚀研究进展

分别从交流电腐蚀的特点、机理、影响因素以及对阴极保护和微生物腐蚀影响的角度,对近年来国内外开展的交流电腐蚀研究进行系统综述。通过对目前研究中存在的重点问题进行综合分析,展望这一领域的研究前景及发展趋势,为相关领域的研究人员提供新思路。     

Corrosion monitoring of nickel-containing steels in marine atmospheric environment

Corrosion monitoring of nickel-containing steels has been performed in a natural atmospheric environment using AC impedance technique. A pair of identical comb-shape steel electrodes embedded in epoxy resin was used as a probe electrode for the corrosion monitoring. Three different probes of ordinary carbon steel, 2.5%Ni- and 5%Ni-containing steels were exposed to a natural marine atmosphere for the period of 14 months. The instantaneous corrosion rate of the steels was monitored by continuous measurements of the polarization resistance, and time of wetness of the steel surface was determined from high frequency impedance. The measurement was automatically carried out with an AC corrosion monitor placed at the exposure site, and data transmission between the exposure site and laboratory was performed through cellular phones.     

一种交流阻抗和弱极化相结合的腐蚀速度测量方法

提出了交流阻抗和弱极化技术相结合的腐蚀速度测量的方法，并依此研制了CMB-4510腐蚀速度测量仪.有效地解决了线性极化技术因估算塔菲尔系数所带来的理论误差，进一步消除了因介质电阻IR降的影响产生的测量误差.结果表明，CMB-4510腐蚀速度测量仪测得的几种体系的腐蚀速度、极化电阻以及介质电阻与M398所测得结果相同；测量缓蚀剂的缓蚀效果与挂片失重法的测试结果完全吻合.     

The corrosion behavior of 70/30 copper‐zinc alloy under the biofilm of sulfate‐reducing bacteria

A laboratory study was carried out on the effect of the biofilm of sulfate‐reducing bacteria (SRB), which plays an important role in corrosion of 70/30 copper‐zinc alloy in culture media under anaerobic condition. The API medium was used to culture the SRB in Zhongyuan oilfield. Potential/time measurement showed that the presence of SRB makes the corrosion potential more active with SRB growth metabolite. Electrochemical impedance spectroscopy (EIS) was used to analyse the electrode process of 70/30 Cu‐Zn alloy with SRB biofilm. Scanning electron microscopy (SEM) examinations revealed the formation of biofilm and corrosion products during exposure to SRB‐containing culture medium. X‐ray diffraction and EDS were used to analyse the corrosion products. The results show that the variation of activity of the SRB biofilm changes with SRB growth by the linear polarization resistance (R_p) and the EIS in culture medium inoculated SRB.     

Influence of regulated modification of nitride layer by oxygen on the electrochemical behavior of Ti–6Al–4V alloy in the Ringer's solution

The corrosion behavior of oxynitrided Ti–6Al–4V alloy was investigated in the Ringer's solution (simulated body fluid) at a temperature of 37°C. The oxynitriding of the alloy was carried out by leaking controlled oxygen‐containing medium into the reaction chamber at the final stage of the nitride formation. It was determined that oxynitriding improved corrosion resistance of Ti–6Al–4V alloy as it provided lower corrosion current density by 1.3–1.5 times and higher corrosion potential. In this paper, we analyzed that the resistance of the double layer had increased with the increase of the oxygen content in titanium oxynitride. Its value was higher compared with untreated alloy, indicating higher corrosion resistance of the oxynitrided one.     

The effect of CeCl3 inhibitor on the localized corrosion of stainless steel in chloride solutions

Stainless steels have been used extensively in many sectors such as medical and household appliances as well as construction. This has been primarily due to their high resistance to corrosion attacks, reasonable cost, and excellent mechanical properties. However, when placed in corrosive media stainless steel is susceptible to localized corrosion attacks, especially when placed in chloride solutions. The paper explores the issue of corrosion liability of austenitic (AISI 316) and duplex (UNS S32205) stainless steels in et aconditions of seawater environment as well as under the influence of an inhibitor in the same environmental conditions. The behavior of stainless steels was examined via electrochemical testing relying on DC and AC techniques, optical metallographic analysis, scanning electron microscopy, and X‐ray diffraction analysis. Duplex stainless steel showed better resistance to localized corrosion but a higher tendency toward general corrosion in all examined solutions. Cerium chloride in a chloride solution showed inhibiting properties for both the AISI 316 and the UNS S32205.