Corrosion Behavior of IN-800 Superalloy in Waste-Incineration Environments: Hot Corrosion by Molten Chlorides

The corrosion resistance of the IN-800superalloy in contact with a molten mixture of (52-48)mol.% PbCl₂-KCl, similar to that found inwaste-incineration plants, has been studied. Thecorrosion kinetics have been analyzed using continuous-currentelectrochemical techniques and electrochemical-impedancespectroscopy (EIS). Studies were performed to determinethe influence of temperature and of the presence of carbon in the salt on the corrosion rate.Scanning electron microscopy (SEM) and electron probemicroanalysis (EPMA) were used as additional techniquesto analyze the corrosion products in order to elucidate the corrosion mechanism.     

Hot Corrosion Behavior of CM 247 LC Alloy in Na2SO4 and NaCl Environments

Hot corrosion studies of CM 247 LC alloy werecarried out in pure sodium sulfate, as well as sodiumchloride and sodium sulfate mixtures of differentconcentrations at various temperatures. A crucible test was employed to study the suitability of CM 247LC as a gas turbine blade material. It was observed thatbare CM 247 LC was severely corroded in just 4 hr, whileit was completely consumed in 70 hr when tested in 90% Na₂SO₄ +10% NaCl at 900°C. The results show that a chloridecontaining melt is more corrosive than pure sodiumsulfate. The weight loss is linearly related tot^1/2 (time) and temperature in the different environments studied. Thecorroded samples were characterized by EPMA, SEM, XRD,and metallographic techniques. The results show that hotcorrosion of CM 247 LC is an electrochemicalphenomenon.     

Strengthening of a 12CrMoV turbine blade steel by retempering

Commercially available martensitic 12CrMo, 12CrMoV, and HCrMoVNb steels in the tempered condi-tion are often used to fabricate turbine blades. Tempering, done at the processing stage itself, is usually carried out at a temperature approximately 100 to 150 ° above the service temperature. At the service temperature, the steel undèrgoes a second tempering. The effect of this second tempering at a lower tem-perature on the strength of 12CrMoV steel is delineated and discussed in this paper.     

Corrosion protection of steel reinforcement by a pretreatment in phosphate solutions: assessment of passivity by electrochemical techniques

Abstract

The aim of this work is to study the protection of steel reinforcement against corrosion by pretreatment in phosphate (Na₃PO₄) solution. The work has been carried out using electrochemical techniques, i.e. corrosion potential E _corr, polarisation resistance R _P and electrochemical impedance spectroscopy (EIS) measurements. The results have been validated by a gravimetric method. It has been stressed that R _P measurements, determined by DC techniques, include the charge transfer resistance R _t plus the resistance associated with the redox process R _ox, both determined by EIS. Also the results have demonstrated that the treatment of the rebar by immersion in the Na₃PO₄ (0·5M) solution favours the formation of a passive layer on the steel rebar surface, which is able to resist longer the action of chlorides to initiate corrosion. However, the resistance of the passive layer against chloride depends on the duration of the treatment by immersion of the rebar within the phosphate solution.     

347不锈钢在硝酸熔盐中的腐蚀行为研究

通过2000 h浸泡实验,研究了347不锈钢在565 ℃下硝酸熔盐 (60%NaNO₃+40%KNO₃) 中的静态腐蚀行为。采用增重法测量347不锈钢在不同时段的重量变化,得到材料的腐蚀动力学曲线,利用XRD、SEM/EDS对347不锈钢表面及横截面腐蚀产物形貌、成分和结构进行分析,并讨论相关腐蚀机理。结果表明,347不锈钢在565 ℃下硝酸熔盐中的腐蚀表现为增重,前300 h腐蚀速率很快,300 h后腐蚀速率逐渐减缓。随着腐蚀时间延长,其表面氧化层中的尖晶石形状逐渐由针状和片状转变为块状,2000 h时基本全部趋于块状。腐蚀达到2000 h时,347不锈钢的外层腐蚀产物厚度均匀且较疏松,并且出现一定程度的开裂,由Fe₂O₃和NaFeO₂组成;内层腐蚀产物厚度不均匀且较致密,主要为 (Fe,Cr)₃O₄。     

CrMoV钢板条马氏体塑性变形诱发内生复合效应的研究

采用力学性能试验、TEM及SEM研究了 15CrMnMoV钢板中的内生复合效应。结果表明 :将15CrMnMoV钢板冷轧而制备的内生复合钢板 ,其σ0 2 在 15 0 0～ 16 6 0MPa之间 ,KIC 在 98 6～ 110 7MPa·m1 2 之间 ,KISCC在 75～ 95MPa·m1 2 之间 ,表现出了超高强韧性 ;内生复合效应的本质在于塑性变形使得 15CrMnMoV钢板成为 (10 0 )织构取向带镶嵌于 (111)织构取向带中的复合结构 ,弱界面为 (10 0 ) (10 0 )晶间界面 ,裂纹扩展过程中弱界面的分层现象使得其断裂韧度大幅度提高。     

The Electrochemical Behavior of Oceanic Microbiological Influenced Corrosion on Carbon Steel

The corrosion behavior of carbon steel in the medium of marine microorganisms was investigated by electrochemical impedance spectra, polarization curves, and so on. Experimental results showed that the corrosion potential of carbon steel moved in a negative direction in the unpurified marine microorganism solution, and the polarization style of the cathodic process did not change. The electrochemical impedance spectra showed that the impedance value of the electrode decreased in the medium with bacteria, which indicated that the existence of microorganism could accelerate the corrosion progress of carbon steel.     

2A12-T4铝合金在盐雾环境下的腐蚀行为与腐蚀机理研究

采用失重法、扫描电镜 (SEM)、X射线衍射仪 (XRD) 和电化学技术研究了2A12-T4铝合金在盐雾环境下的腐蚀规律及机理。结果表明：2A12-T4铝合金的腐蚀失重量与腐蚀时间符合幂指数函数规律。腐蚀初期,在Cl^-作用下2A12-T4合金发生点蚀,随后点蚀发展为全面腐蚀,电化学腐蚀产生大量Al(OH)₃导致疏松腐蚀产物层增厚;腐蚀中、后期,外层腐蚀产物发生脱落,剩余致密堆叠的腐蚀产物层。电化学测试表明,随着腐蚀时间的延长,2A12-T4合金的自腐蚀电流密度先减小后增大再减小,容抗弧先收缩后扩大,最后略有收缩。     

304不锈钢在模拟废吸收液中的腐蚀行为初步实验研究

通过对304不锈钢挂片进行静态实验和动态实验,得出:在温度为25℃、60℃,pH=7、8的含氯模拟废吸收液中,当氯离子浓度为0.29mol/L时,挂片未腐蚀,改变溶液配制方法,提高浓度为0.4652mol/L,挂片仍未腐蚀。     

模拟塔里木油田环境中低Cr钢的H2S/CO2腐蚀行为

通过高温高压腐蚀试验,运用SEM、XRD、EDS等分析技术.研究了普通P110与3Cr110钢在模拟塔里木油田现场环境中的CO2/H2S腐蚀特征.结果表明:在模拟CO2腐蚀环境中,这两种材料的腐蚀产物为FeCO3,3Cr110表现出良好的抗CO2均匀腐蚀及局部腐蚀能力,其平均腐蚀速率显著小于普通P110;模拟CO2/H2S腐蚀条件下,两种材料的均匀腐蚀速率远小于单独CO2腐蚀环境下的均匀腐蚀速率,表面腐蚀产物为FeS,H2S腐蚀占主导作用,Cr元素在低Cr钢腐蚀产物膜中的富集,其腐蚀产物Cr(OH)3改善了腐蚀产物膜的稳定性,显著提高了低Cr钢的抗均匀腐蚀及局部腐蚀能力.     

月桂酸根离子的吸附及其对N80碳钢垢下局部腐蚀的影响

利用一种闭塞腐蚀电池装置,采用极化曲线和电化学阻抗方法研究了月桂酸根离子C12H23OO-在中性NaCl溶液中在N80钢表面的吸附及其对垢下闭塞微区的影响。结果表明,C12H23OO-在耦合电流作用下迁入闭塞区后在碳钢表面形成单分子层吸附膜,抑制了电极反应的阴极过程。C12H23OO-的吸附行为符合Flory-Hug-gins等温线模型。C12H23OO-吸附膜改变了电极表面双电层结构,使金属表面膜层更加致密有序,抑制了基底金属的进一步腐蚀。     

深冷处理对EH40极寒环境船用钢板的海水腐蚀性能影响

采用模拟浸泡实验技术,结合腐蚀形貌分析以及动电位极化和电化学阻抗技术研究了深冷处理对EH40极寒环境船用钢板在3.5%(质量分数)NaCl溶液中的海水腐蚀行为。结果表明:未经深冷处理的极寒环境船用钢板表面发生均匀腐蚀,在样品表面有均匀致密的腐蚀层产生;而经过-80℃深冷处理的钢板试样表面发生点蚀现象,其腐蚀失重增加,腐蚀速率由1.15 mm/a升至1.33 mm/a,增幅约为15.6%,同时腐蚀电流密度由1.244μA·cm^-2升至3.643μA·cm^-2,电化学阻抗值减小,耐蚀性降低;两者的腐蚀产物以α-FeOOH、β-FeOOH和γ-FeOOH为主。较低的环境温度对于极寒环境船用钢板的耐腐蚀性能有一定的影响。     

硫酸盐还原菌在不同氧环境下对A3钢腐蚀的研究

通过静态培养实验,研究了在不同的氧环境下,硫酸盐还原菌对A3钢腐蚀的规律。实验结果表明,在相同的培养基中,严格厌氧条件下的硫酸盐还原菌对A3钢的腐蚀速率与连续的厌氧-有氧交替变换条件下的硫酸盐还原菌腐蚀的速率相差不是十分明显。     

Hastelloy N合金表面激光熔覆NiCoCrAlY涂层在LiF-NaF-KF熔盐中的腐蚀行为研究

采用激光熔覆同步送粉技术在HastelloyN合金表面制备了NiCoCrAlY涂层,研究了HastelloyN基材和含NiCoCrAlY涂层的HastelloyN试样在900℃LiF-NaF-KF熔盐中的腐蚀行为。利用失重腐蚀法评估了试样的耐熔盐腐蚀能力,采用XRD和SEM表征了基材和涂层的物相组成、显微组织和腐蚀形貌,并结合EDS分析了微区成分。结果表明,NiCoCrAlY涂层试样的腐蚀速率仅为Hastelloy N基材的2/3。Hastelloy N基材表现为晶间腐蚀,其中Cr元素沿晶界发生选择性脱溶腐蚀,腐蚀前由γ-Ni和M_6C(M为Ni、Co、Cr等)等物相组成,腐蚀后新析出Co_9Mo_(21)Ni_(20)相。NiCoCrAlY涂层表现为均匀腐蚀,其中Al元素充当"消耗品"由涂层均匀向外扩散,形成的腐蚀产物可阻碍涂层中其它元素的扩散从而保护基材,腐蚀前主要由γ-Ni、Al_(0.983)Cr_(0.017)、AlNi_3等物相组成,腐蚀后只存在γ-Ni相。NiCoCrAlY涂层显著提高了基材的耐熔盐腐蚀性能。     

受力的LY12和LC4铝合金在中国西部盐湖大气环境中的腐蚀行为

通过现场大气暴露实验,利用金相显微镜和SEM等手段分析试样表面和截面形貌,研究了U弯受力状态下包铝与无包铝的LY12和LC4两种铝合金在我国西部盐湖大气环境中的腐蚀行为。结果表明,包铝的两种铝合金的腐蚀主要发生在包铝层,以点蚀为主,未观察到包铝层被穿透现象。无包铝的铝合金试样都发生了明显的沿晶应力腐蚀开裂,其中LY12铝合金在拉应力和压应力下都有较多的应力腐蚀裂纹,LC4铝合金只在拉应力下观察到了裂纹;两种铝合金在压应力下都发生了剥层腐蚀,拉应力下剥层腐蚀受到抑制。     

7A04和2A12铝合金在吐鲁番干热大气环境中的腐蚀行为

采用现场暴晒试验,研究了7A04和2A12两种铝合金在吐鲁番干热大气环境中的腐蚀行为和机理。1a暴露后的失重分析发现7A04的腐蚀速率大于2A12;采用SEM和EDS观察分析了两种合金表面的腐蚀产物,结果表明,均主要由铝的氧化物和氢氧化物组成。去除腐蚀产物后,7A04表面呈现大量密集腐蚀坑,而2A12表面腐蚀坑则较少。EIS结果表明,两种合金的腐蚀产物层电阻电容差别较大,带腐蚀产物2A12的耐蚀性优于7A04。     

正交试验法研究X90管线钢在CO_2环境中的腐蚀行为

通过正交试验法研究了CO_2环境中各因素对X90管线钢腐蚀行为的影响。结果表明:各因素对X90管线钢在CO_2环境中腐蚀速率的影响按大小顺序是原油含水率、温度、CO_2分压、流速;X90管线钢腐蚀产物膜表面布满网状裂纹,呈鳞片状,产物膜结构疏松,对基体保护作用较弱,表面点蚀坑较多,点蚀严重,X90管线钢抗CO_2腐蚀性能较差;产物膜成分随腐蚀环境变化而不相同,所有产物中都含有FeCO_3和Fe,部分试样产物膜中还有腐蚀介质析出的碳酸盐。     

国产镀锌钢在不同水环境中的腐蚀行为:I淡水和盐水

利用电化学阻抗谱和电化学噪声技术对比研究了国产镀锌钢板在盐水和淡水中的腐蚀行为。结果表明,镀锌钢在两种水溶液中的腐蚀均可分为3个阶段,不同阶段表现出完全不同的电化学特征,镀锌钢在盐水中的腐蚀速率明显高于其在淡水中的腐蚀速率,其在盐水中的腐蚀产物呈棒状或片层状,对基体不具有保护性,而在淡水中的腐蚀产物形态呈规则的球状,对基体具有明显的保护作用。     

国产镀锌钢在不同水环境中的腐蚀行为:II反渗透水和调质水

利用开路电位测量、电化学阻抗谱测试技术,结合微观形貌观察,对比研究了国产镀锌钢板在不同反渗透水中的腐蚀行为,镀锌钢在不同进水盐度所得的反渗透水中的腐蚀失效表现出了相似的电化学特征,通过CaCl2、NaCl和NaHCO3等对反渗透水的水质进行调整,改变了镀锌钢的腐蚀失效历程,这可能与腐蚀产物膜的脱落和附着密切相关。     

十二烷基二羟乙基氧化胺在0.5 mol·L~(-1) H_2SO_4中对A3钢的缓蚀性能

通过失重法、电化学方法和量子化学计算法研究了十二烷基二羟乙基氧化胺(OAE-12)在0.5mol·L~(-1)H_2SO_4中对A3钢的缓蚀性能和作用机理。结果表明,在0.5mol·L~(-1)H_2SO_4中OAE-12能同时抑制A3钢的阴、阳极反应,缓蚀性能显著,当OAE-12质量浓度仅为200mg·L-1时,失重试验所得缓蚀率可达93.59%,且失重法、动电位极化曲线法、电化学阻抗谱法测试结果具有一致性;通过量子化学计算结果可知,OAE-12缓蚀作用机理可能是源于其分子内的氮、氧与钢表面的铁的相互作用。