New Problems of Boiler Corrosion after Coupling Combustion of Coal and Biomass and Anti-Corrosion Technologies

This study explores the corrosion issues arising from the coupled combustion of coal and biomass and proposes potential solutions.Biomass,as a renewable energy source,offers advantages in energy-saving and carbon reduction.However,the corrosive effects of alkali metal compounds,sulfur(S)and chlorine(Cl)elements in the ash after combustion cannot be underestimated due to the high volatile content of biomass fuels.We investigate the corrosion mechanisms,as well as the transfer of Cl and alkali metal elements during this process.Comparative corrosion analyses are conducted among coal-fired boilers,pure biomass boilers and boilers with coupled combustion.Various biomass types in co-firing are studied to understand different corrosion outcomes.The main factors influencing corrosion include the physicochemical properties of biomass feedstock,furnace temperature and heating surface materials,with the chemical composition and ash content of biomass playing a dominant role.Currently,the methods used for anti-corrosion include water washing pretreatment of biomass feedstock,application of novel alloys and coatings and the development of additives to inhibit fouling,ash deposition and corrosion.Efficient inhibitors are economical and easy to produce.Additionally,biomass can be converted into biomass gasification gas,although challenges related to tar still need to be addressed.

Model test of the stability degradation of a prestressed anchored rock slope system in a corrosive environment

The long-term stability of a prestressed anchored slope might be influenced by the durability of the anchorage structure.To understand long-term stability of anchored rock slopes,the research presented herein evaluated the performance evolution of a prestressed anchored bedding slope system in a corrosive environment by model test.The corrosion process in a prestressed anchor bar was monitored in terms of its open-circuit potential(OCP),corrosion current density(CCD),and electrochemical impedance spectroscopy(EIS).The stability of the prestressed anchored slope was evaluated by monitoring changes in anchorage force and displacements.The experimental results show that prestress and oxygen could reduce the corrosion resistance of the anchor bar,and anchor bars in a chloride-rich environment are very susceptible to corrosion.Prestressed tendons in a corrosive environment suffer a loss of anchorage force,the prestress decreases rapidly after locking,and the rate thereof decreases until stabilising;in the later stage,corrosion leads to the reduction of the cross-sectional area of the steel bar which may cause the reduction in anchorage force again.Anchorage force controls the deformation and stability of the anchored slope,the prestress loss caused by later corrosion may lead to an increased rate of displacement and stability degradation of the prestressed anchored rock slope.

ELECTROCHEMICAL MEASUREMENTS FOR MARINE ATMOSPHERIC CORROSION STUDIES USING KELVIN PROBE REFERENCE ELECTRODE

A Kelvin probe was used as reference in this study on electrochemical measurements of a simulatedmarine atmospheric corrosion system (electrode covered by a very thin electrolyte layer). The experimentalsetups for improved measurements proved satisfactory for the conventional steady-state electrochemicalmeasurements in atmospheric studies.

Carbonation Resistance and Anticorrosive Properties of Organic Coatings for Concrete Structures

The present study examines the behavior of three major categories of organic coatings which are applied on the surface of concrete structures and specifically conventional, high performance and nanotechnology paint systems. The comparison is achieved in the means of anticorrosion properties under the presence of chloride ions and carbonation resistance. The evaluation methods included electrochemical measurements in order to assess corrosion properties and the determination of steel’s mass loss after the end of the experimental procedure. Carbonation depth was measured using phenolphthalein as indicator after accelerated and physical exposure. From the results so far it can be shown nanocoatings gave promising results regarding induced chloride ion corrosion.

Corrosion Measurements of Reinforcing Steel by Different Electrochemical Techniques

Electrochemical techniques of the corrosion measurements of reinforcing steeI in concrete have been evaluated. These techniques include half-cell potential measurements, impressed voltage method, impressed current method and potentiostatic polarization technique. The results of corrosion behaviour of the steel in both 5%NaCl and 5%MgSO4 show that each electrochemical technique provides some information about the condition of the steel bar or the corrosivity of the environment being evaluated, yet none provides a complete data regarding the corrosion resistance of reinforcing steel in aggressive media

Durability of Reinforced Concrete Beams under Simultaneous Flexural Load in Corrosive Environment

The deterioration of concrete over time is the result of various mechanical, physical, chemical and biological processes, with the corrosion of reinforcement being the most serious problem of durability of reinforced concrete structures. Over the last 50 years, a tremendous effort has been spent by the international scientific community with laboratory research and experimental field studies in order to increase the resistance of concrete over corrosion. This paper presents an experimental study of the corrosion behaviour of reinforced concrete beams with simultaneous sustained flexural loading. For this purpose, 40 reinforced concrete beams of 5 different compositions were constructed and exposed in simulated harmful environmental conditions in 3 different stress ratios for a total period of 42 months. Their behavior against corrosion was determined via regular measurements of the electrical resistance of concrete (according to ASTM G57) and the corrosion potential of the steel-reinforced bars with the use of copper sulphate (CSE) as reference electrode (according to ASTM C876). A theoretical calculation of the corrosion rate was conducted based on the electrochemical measurements of the beams. The results indicate that the corrosion potential of steel decreased in time and more rapidly after the initiation of the corrosion process;the electrical resistance firstly increased, remained stable for a short period and then decreased with the corrosion development, as expected. An inversely proportional relationship of the water/cement ratio of a composition with its corrosion behaviour as well as an analogous relationship between the cement content of a composition and its corrosion behaviour was observed. Also, the corrosion rate of steel is increased gradually with increasing load.

Monitoring of the Corrosion on a Steel Sheet-Pile Marine Breakwater by Systematic Thickness Measurements

In Quepos, Pacific of Costa Rica, it was finished on 2010 the first phase of a marina, including two mix breakwaters, with rubble mound （rocks and concrete units）, and 25 circular steel sheet piles cofferdam cells, filled with sand and gravel. The maintenance plan, considers tracking sheet pile corrosion, comparing ＂actual＂ against expected rates, checking structural limits, and programming countermeasures if accelerated corrosion is identified. Specific control sections, along the breakwaters, both inside and outside the basin, were established. In each section, thicknesses were measured every meter from the top of the steel cell to seabed using an ultrasonic equipment, and an underwater transducer. Both land crew, and divers for submerged portions, were used. The measurements campaigns are for several years from 2011 to 2016. Sectors of the breakwater with varied corrosion attack levels could be differentiated. Also, corrosion rates and lifespans were estimated, both general for the structures, and specific for each section and level. In turn, this allowed to identify maintenance priorities, defining sites where measures of corrosion protection should initiate, as well, to have confidence in the structural capacity and safety of the breakwaters.

Monitoring of the Corrosion on a Steel Sheet-pile Marine Breakwater by Systematic Thickness Measurements

In Quepos,Pacific of Costa Rica,it was finished on 2010 the first phase of a marina,including two mix breakwaters,with rubble mound(rocks and concrete units),and 25 circular steel sheet piles cofferdam cells,filled with sand and gravel.The maintenance plan,considers tracking sheet pile corrosion,comparing'actual'against expected rates,checking structural limits,and programming countermeasures if accelerated corrosion is identified.Specific control sections,along the breakwaters,both inside and outside the basin,were established.In each section,thicknesses were measured every meter from the top of the steel cell to seabed using an ultrasonic equipment,and an underwater transducer.Both land crew,and divers for submerged portions,were used.The measurements campaigns are for several years from 2011 to 2016.Sectors of the breakwater with varied corrosion attack levels could be differentiated.Also,corrosion rates and lifespans were estimated,both general for the structures,and specific for each section and level.In turn,this allowed to identify maintenance priorities,defining sites where measures of corrosion protection should initiate,as well,to have confidence in the structural capacity and safety of the breakwaters.

海洋工程管道腐蚀损伤深度无损评价方法

海洋工程管道服役安全长期受到环境腐蚀的严重威胁,管道腐蚀损伤评价对保障国民经济和社会的可持续发展具有重要意义。介绍了切向法和灰度法射线检测在定量测定腐蚀损伤深度方面的原理,分别对两种方法的检测误差进行了理论分析,基于径向和轴向穿透厚度变化规律,提出了灰度法射线检查厚度修正方法。以平底阶梯孔试样为试验对象,分别进行切向法和灰度法射线检测。结果表明:测量误差较小,切向法和灰度法射线检测均可用于管道腐蚀损伤深度无损评价。

顺丁橡胶装置溶剂管线腐蚀泄漏原因分析及防腐对策

某石化公司的顺丁橡胶装置发现溶剂管道出现了腐蚀穿孔问题。为了找到管道失效的根本原因,对腐蚀管道进行了取样,并进行了宏观检查、化学成分分析、硬度测量、金相组织分析、微观形貌分析以及腐蚀产物能谱分析等检验与分析。结果显示,管道的化学成分、力学性能及金相组织均符合要求。然而,微观形貌分析发现腐蚀区域呈现沿晶选择性腐蚀,能谱结果显示腐蚀区域含有较高量的氟元素。综合考虑到腐蚀主要发生在焊缝附近,焊缝的凸起和沟槽会在该区域形成涡流和低压区,导致管道内上层气相区的氢氟酸(HF)浓度过高,从而对管壁组织变化区域产生选择性晶间腐蚀。因此可以判断氢氟酸(HF)腐蚀是导致溶剂管道腐蚀穿孔的根本原因。针对管道失效原因,提出了在焊接施工、工艺操作和材质升级方面的建议措施,以避免和预防类似失效,从而提高设备的安全性。

金秋区块致密气微生物腐蚀控制措施研究及应用

金秋区块致密气是采取加砂压裂工艺进行开采的,在产出水中存在硫酸盐还原菌(SRB)、腐生菌(TGB)和铁细菌(FB)等微生物,研究并证明其存在微生物腐蚀风险,并针对该现象开展了微生物来源和微生物腐蚀控制措施的研究。自从采取控制措施后,截止目前各平台井井筒及集输系统均未发生微生物腐蚀失效现象。

Corrosion behavior of T2 copper in 3.5% sodium chloride solution treated by rotating electromagnetic field

Copper is susceptible to producing corrosion problems in corrosive environments, which leads to serious safety problems. Thus, investigating the corrosion behavior of copper is of great significance. The effects of rotating electromagnetic field on corrosion behavior of T2 copper in 3.5% sodium chloride solution with electrochemical measurements were investigated. The results showed that rotating electromagnetic field changed properties of 3.5% sodium chloride solution by increasing the values of temperature and pH and decreasing the values of conductivity and dissolved oxygen. The rotating electromagnetic field improved the corrosion resistance of T2 copper. The corrosion products of T2 copper in treated 3.5% sodium chloride solution were composed of Cu20 and CuCl. The low corrosion rate of T2 copper was resulted from the decrease of dissolved oxygen in 3.5% sodium chloride solution treated by rotating electromagnetic field.

电网设备中不锈钢部件的腐蚀特征

不锈钢具有优良的耐腐蚀特性,在电网输变电设备中得到广泛应用,但在设备检修中也发现了大量不锈钢部件腐蚀与损坏的案例。通过变压器油色谱在线监测装置、换流站阀冷系统均压电极、隔离开关、管道法兰盘和电流互感器等失效案例介绍了不锈钢部件的腐蚀特征与原因;根据不锈钢的腐蚀类型,总结了其腐蚀机理与特点,提出了电网设备中不锈钢腐蚀的防护措施,为电网不锈钢部件的腐蚀控制工作提供参考。

某型船海水冷却系统蝶阀腐蚀机理分析及改进措施

为了确定某型船蝶阀严重腐蚀原因,对所在系统进行整体分析,总结归纳当前船舶海水冷却系统腐蚀机理及防腐措施。通过系统分析、宏观检查、化学成分检验、金相组织观察,以及扫描电镜观察,分析腐蚀原因,确定产生腐蚀的关键因素为该蝶阀阀盘在热处理过程中冷却速度控制不当,产生亚稳态组织,在海水冷却系统中发生脱成分腐蚀和氧化腐蚀。在后续船舶设计建造过程中,从管路及附件材质要求、海水设计流速、系统工艺设计、管子制造工艺,以及防海生物等方面,给出海水冷却系统防腐的改进措施和系统方案,实船应用效果良好。

锆合金腐蚀与防护研究进展

锆合金以其优异的核性能和生物相容性被广泛应用于民用发电反应堆、核动力航空母舰、核潜艇、空间飞行器的结构材料以及医用材料,在苛刻环境下服役的锆合金同样面临腐蚀失效的风险。由于材料本身服役环境的特殊性,使得锆合金腐蚀研究的模拟测试难度加大,诸多疑问难以得到有效解答。锆合金的腐蚀形式包括均匀腐蚀、疖状腐蚀、应力腐蚀以及微生物腐蚀,其腐蚀也受材料成分、热处理工艺、表面粗糙度、氧化膜成分、溶液的pH值、辐照、热流水化学环境以及温度等因素的影响,防护措施包括涂层和缓蚀剂等方式。为进一步改善锆合金的耐蚀性能,未来可从以下几方面展开研究:1)锆合金基体中固溶元素的浓度;2)第二相元素类型、晶粒尺寸及分布;3)氧化膜的生长机制;4)细菌附着方式和生物被膜生长行为等。

油气管道化学腐蚀机理分析及其防护措施

通过采用电化学阻抗谱、盐雾实验以及温度循环等分析方法,评价了环氧树脂、聚氨酯、锌基涂层以及新型复合材料涂层在模拟的盐水、酸性及碱性环境中的腐蚀行为。结果表明:在酸性环境中,管道材料的腐蚀速率最高,达到0.60 mm∙a^(-1),而碱性环境下最低,仅为0.20 mm∙a^(-1)。此外,阻抗分析揭示,酸性环境中的阻抗值从初始的1510Ω·cm^(-2)降至312Ω·cm^(-2),反映出腐蚀介质对防护层的破坏特别迅速和严重。新型复合材料涂层及阴极保护系统能显著提高腐蚀防护效能。阴极保护系统将腐蚀速率降至0.06 mm∙a^(-1),显示出较牺牲阳极保护(腐蚀速率为0.14 mm∙a^(-1))更为优异的防护效果。现场数据显示,采用新防腐技术的管道在实际应用中腐蚀速率显著降低。经过4年的运行后,使用新技术的设施腐蚀速率仅增加至0.6 mm∙a^(-1),而传统防腐措施的设施腐蚀速率增至2.0 mm∙a^(-1)。

中国西部某油田管道失效原因及防护措施

对西部某油田管道失效数据进行统计分析,结合细菌检测、水质与土壤分析等手段对管道失效原因进行了分析。结果表明:内外腐蚀穿孔是造成该油田管道失效的主要原因;管道运行年限长、制造工艺缺陷、内外环境介质腐蚀性强、细菌加速腐蚀、缺乏有效腐蚀防护措施、施工过程不规范是该油田管道内外腐蚀的重要原因。通过失效原因分析、选用耐蚀性管材、采用适用性强的防腐蚀层和腐蚀抑制剂、建立现场腐蚀监测系统,可对油田管道腐蚀进行综合性治理防控。

常减压蒸馏装置加工负荷变化及腐蚀风险研究

对常减压蒸馏装置的电脱盐控制情况、加工原料的腐蚀性以及加工负荷变化等方面进行分析,并针对装置的塔顶低温系统和高温部位的腐蚀控制情况以及腐蚀风险进行了系统的评估,并提出了一系列针对腐蚀的控制措施和建议,以确保装置的长期可靠运行,旨在降低装置内金属材料的腐蚀风险,维护装置性能和延长装置的寿命。

STUDY ON CORROSION BETWEEN FLEXIBLE GRAPHITE AND METAL AND ITS PROCTECTION

In this paper, the mechanism of corrosion between flexible graphite which is used as a sealing material and metal is in-vestigated, the anticorrosive measures are introduced, and some mordern measures which should be paid attention are provided.

直流杂散电流对埋地管道的电腐蚀规律及排流措施

随着工业化进程的不断发展,轨道交通对埋地管道的直流杂散电流干扰愈发严重。为降低杂散电流引发的电腐蚀问题,在监测埋地管道沿线电位的基础上,分析干扰规律、干扰频率、干扰源位置对管道的影响,考察电流流入和流出的规律,并测试不同排流措施效果。结果表明:干扰规律与轨道的运营状态保持一致,干扰频率与发车时间间隔保持一致;距离干扰源越近,电位正向偏移的时间比例越大,腐蚀趋势远大于其余管段;同一位置不同时段可能互为电流流入、流出段,电流流动方向和规律随时间动态变化;排流措施中强制排流的效果最好,其次为极性排流和接地排流,阴极保护的效果较差;通过多重联合防护,除与轨道交通最近的管段外,其余管段均达到了良好的保护效果,腐蚀速率大幅降低,可减少管道更换和泄漏放空量。