Chloridation-oxidation of nine commercial high-temperature alloys at 800°C

Chloridation-oxidation studies of nine commercial high-temperature alloys were carried out at 800°C in three different H₂-HCl-H₂O() environments: (A) both low HCl and H₂O() partial pressures, where either Cr₂O₃ or FeCr₂O₄ is stable, (B) both high HCl and H₂O() partial pressures, where FeCrO₄ is stable and CrCl₂ is metastable, and (C) high HCl partial pressure in the absence of H₂O(), where either CrCl₂ or Cr₂O₃ is stable. Although alloy 600 has the lowest Cr content of these nine alloys, it showed excellent corrosion resistance in all three environments because of its high Ni content. Alloy 304, with the lowest Ni content of the nine alloys, exhibited poor corrosion resistance in the environment C, fair resistance in the environment B and good resistance in the environment A. Alloy 800 showed very good resistance in Environment A, and fair corrosion resistance in Environment B; however, it suffered linear weight-loss kinetics when exposed to Environment C The alloys 617, 214, HR-160, X, 230 and 86 have good corrosion resistance in Environments A and B because of their relatively high contents of oxide-scale-forming elements Cr and/or Al. In Environment C, chlorine dramatically decreased the adhesion of the scale on the surface, and aluminum in alloys 617 and 214 hardly showed its usual beneficial effect in combating corrosion, nor does silicon in alloy HR-160. Different corrosion mechanisms are proposed for the alloys in the different environments.     

氯化钾转化地面的腐蚀与防护

分析了氯化钾低温转化法生产硫基NPK复合肥转化地面的腐蚀机理，并提出了相应的防护措施。     

Effect of Mo on corrosion behavior of Ni20Cr–xMo alloys in air with NaCl–KCl–CaCl2 vapor at 570°C

The effect of Mo on the corrosion behavior of Ni20Cr–xMo alloys in an oxidizing chlorine-containing atmosphere using air mixed with the salt-vapor mixture of NaCl–KCl–CaCl₂ at 570°C was investigated. The results revealed that the corrosion performance of the Ni20Cr alloys in the oxidizing chlorine atmosphere was improved by Mo addition of up to 3 wt%. The Mo-free alloy formed a potassium chromate during corrosion as a result of the reaction between the Cr₂O₃ scale and KCl vapor. The chromate formation increased the chlorine potential at the scale surface and induced the breakdown of the protective Cr₂O₃ scale, resulting in internal chromium chloride precipitates and a Cr-depleted zone. In contrast, the presence of Mo resulted in the formation of a NiO scale, which did not react with the salt vapors and, therefore, prevented the formation of chromates. The beneficial effect of Mo on the high-temperature chlorination of Ni–Cr alloys in salt-vapor-containing atmospheres was ascribed to the suppression of chlorine generation due to NiO scale formation.     

G105钻具用钢在8%KCl溶液中缓蚀剂的研究

采用旋转挂片法对G105在8%的KCL溶液中的缓蚀剂进行筛选;通过缓蚀剂加入前后极化曲线的变化,分析了缓蚀剂的缓蚀机理;根据滞后环实验,研究了缓蚀剂在8%KCL溶液中对G105的点蚀抑制作用。结果表明:(1)2%含硅复合缓蚀剂(水玻璃)+10mg/L HEDP+15mg/L氯化锌缓蚀效果最好,其缓蚀率高达98.5%;(2)缓蚀剂的加入对腐蚀反应的阴极过程有明显的抑制作用,同时对腐蚀反应的阳极过程也有一定的抑制作用,该缓蚀剂是以抑制阴极过程为主的混合型缓蚀剂;(3)对点蚀有很好的抑制效果。     

20号钢在HCl-H2S-H2O溶液中的腐蚀行为

利用极化曲线和电化学阻抗,结合扫描电镜和能谱分析,对20号钢在90℃HCl-H2S-H2O溶液中的腐蚀行为进行了研究.结果表明,当溶液中存在H2S时,电极表面形成的FeS膜对HCl的侵蚀具有一定的阻碍作用;随H2S浓度的增加,膜电阻、电荷转移电阻逐渐减小,说明膜的敛密性下降,腐蚀加重;当溶液中HCl较高时,FeS膜出现...     

Corrosion behavior of CuCrNiAl alloy in HCl solutions

1 Introduction Cu alloy has become a kind of important materials for ocean construction as its excellent anti-corrosion performance. Though this kind of alloy has been applied for a long time, it often undertakes serious corrosion, low strength and leakag…     

High-temperature corrosion and creep of Ni-Cr-Fe alloys in carburizing and oxidizing environments

The carburization of NiCr 32 20 and NiCrSi 60 16 has been studied in CH₄-H₂ mixtures in the temperature range 900–1100°C. The methods included thermogravimetric measurements and studies on reacted specimens by X-ray diffraction, metallographic, and chemical analysis. Upon carburization internal carbides M₇C₃ and M₂₃C₆ are formed (M=mainly Cr); the rate of carburization is determined by carbon diffusion in the Fe-Ni matrix with carbide precipitations. The effect of the alloying elements Ni and Si on the carburization resistance of austenitic alloys is explained. By the same methods the oxidation and carburization in CO-H₂O-H₂ mixtures have been studied. The important role of a stable chromium oxide layer for the carburization resistance was confirmed. Creep tests at 1000°C in a CO-H₂O-H₂ atmosphere where Cr₂O₃ is stable showed carburization occurring through cracks in the oxide layer. At high strain rates premature failure occurs by carburization, which is followed by internal oxidation and formation of cracks, voids, and holes.     

The Corrosion Behavior of Four Commercial Steels in Reducing Atmospheres Containing HCl At 773–873 K

The corrosion of four Fe–Cr commercial steels with different chromium contents in a simulated waste-gasification atmosphere containing 0.5 vol. H₂, 0.5 vol. HCl, balance CO₂ has been investigated at 773 and 873 K. The same materials have also been tested in the same gas mixture free from HCl at both temperatures for comparison. The results show that the materials with low-chromium content (2.25CrMoV and NF616) undergo accelerated corrosion in the presence of HCl, while the stainless steel SS304 suffers very little corrosion. On the contrary a steel containing 12 wt. Cr (12CrMoV) corrodes rather rapidly at 773 K but quite slowly at 873 K. The beneficial effect of chromium on the corrosion resistance of the steels increases with the chromium content at both temperatures. The steels tested show corrosion rates generally decreasing with time, having kinetics which are approximately parabolic at 773 K but intermediate between parabolic and linear at 873 K. Only little or even no chlorine can be detected at the scale/metal interface at both temperatures for all materials corroded in HCl-containing atmospheres. The corrosion mechanism can be explained by the so-called active-oxidation model.     

Electrophoretic deposition of MCrAlY overlay-type coatings

A new process, which is a combination of electrophoretic deposition and pack cementation, was used to obtain MCrAlY overlay-type coatings. Using the electrophoretic-deposition process, rare-earth element is added to the deposits by using a special additive which contains yittrium, and excellent high-temperature corrosion resistance was observed after pack cementation.     

International Workshop on High-Temperature Corrosion

The results of a third international workshop on New Knowledge and Open Questions of High-Temperature Corrosion that took place in August 1994 in Gohrisch, Saxony, Germany, are presented. The workshop was sponsored by Stiftung Volkswagenwerk and the Electric Power Research Institute (EPRI). Twenty-eight leading corrosion scientists from Europe, North America, and Australia participated. The discussion of nine subject areas in the form of key questions and proposed answers is presented.     

纯Ni和Ni基合金在ZnCl2—KCl盐膜下的腐蚀

考察了表面涂有ZnCl2-KCl盐膜的纯Ni和M38G,GH864两种Ni基合金在450℃纯氧气氛中的耐蚀性。结果表明：3种材料均发生了加速性腐蚀,形成的表面产物膜十分疏松并与基体的粘附性较差;合金中较高的Cr含量并没有提供良好的保护性,其腐蚀速度高于纯Ni。分析了NiO与Cr2O3氧化膜在该环境中具有不同热力学稳定性的原因,并讨论了材料的加速腐蚀机理。     

茄叶提取液在盐酸介质中对碳钢的缓蚀性能

通过动电位极化曲线法、电化学阻抗法、失重法和扫描电镜法研究了茄叶提取液在1mol·L-1 HCl中对碳钢的缓蚀性能和机理。结果表明:茄叶提取液的最佳提取条件为盐酸浓度3.0mol·L-1、温度55.0℃、时间62h;在最佳条件下提取的茄叶提取液缓蚀性能优异,当茄叶提取液质量浓度为1 800mg·L-1时,失重缓蚀率达92%以上;茄叶提取液在碳钢表面的吸附符合Langmuir吸附等温模型,茄叶缓蚀剂可显著抑制碳钢的腐蚀。     

不同Cr含量的Ni-Cr合金熔覆层的高温氧化和热腐蚀特性

采用激光熔覆技术制备了Cr质量分数为10%、20%和40%的Ni-Cr合金熔覆层,研究了其在900 ℃下的高温氧化特性和600 ℃下Na₂SO₄+25% K₂SO₄混合盐中热腐蚀特性。结果表明,Cr含量对熔覆层的高温特性起着关键作用。提高Cr含量对提升熔覆层抗硫酸盐诱导的热腐蚀能力比提升抗循环高温氧化能力更有效。Cr40涂层抗高温氧化和热腐蚀性能最佳。Cr10的氧化产物以NiO为主,极易脱落,内部氧化严重。虽然Cr40表面可以形成单一的Cr₂O₃层,但热应力和生长应力引起的富Cr氧化物内部开裂,使Cr40的抗循环高温氧化能力仅略好于Cr20。面对热腐蚀时,Cr10表面呈现层状NiO和Ni₃S₂叠层分布的腐蚀产物,内部腐蚀区也生成了Ni的硫化物。Cr20表面Cr₂O₃层被破坏,内部腐蚀严重,生成了CrS。Cr40表面生成了致密的Cr₂O₃保护层,有效地防止了进一步腐蚀。     

磷酸酯基咪唑啉化合物的合成及其在HCl水溶液中的腐蚀抑制机理

目的通过三乙烯四胺和苯甲酸合成IMBT,再利用IMBT、H3PO3和甲醛经过曼尼希反应制得IMBTM,并探究其对碳钢在HCl水溶液中的缓蚀作用。方法采用动态失重法、电化学技术以及热力学等方法研究缓蚀剂IMBT和IMBTM在60℃、1 mol/L的盐酸溶液中对10#碳钢的缓蚀性能和吸附规律。结果利用IR对产物进行表征,均得到了产物特征峰。在动态失重试验中,IMBT和IMBTM两种缓蚀剂的质量浓度为3 g/L时,碳钢的腐蚀速率分别为3.92、2.94 g/(m2·h),缓蚀剂的缓蚀率分别为79.65%和84.75%。极化曲线试验表明随着两种缓蚀剂浓度增加,腐蚀电位正移,阳极电流密度下降明显。交流阻抗的测试显示随着两种缓蚀剂浓度增大,容抗弧半径逐渐增大,且在相同浓度下,添加IMBTM时的容抗弧半径更大。另外,随着缓蚀剂浓度的增加,拟合参数Rct增大、Cdl减小,证明缓蚀剂在金属表面取代了水,并吸附成膜。研究等温吸附模型,发现数据带入Langmuir等温吸附方程后,表现出了很好的线性关系。结论在1 mol/L HCl溶液中,IMBT和IMBTM对10#碳钢均有缓蚀作用,且IMBTM的缓蚀作用较高。两种缓蚀剂均属于阳极型缓蚀剂,对阳极的缓蚀作用较高。且两种化合物在10#碳钢表面上的吸附过程为自发放热过程,其吸附规律遵循Langmuir等温吸附式,属于单分子层吸附。     

咪唑啉类化合物在HCl溶液中对碳钢的缓蚀机理分析

目的 研究咪唑啉（IM）及咪唑啉基脲（IU）在盐酸溶液中对碳钢的缓蚀性能。方法 采用静态失重法、电化学测试技术、表面形貌及官能团分析、热力学等温方程等方法,研究缓蚀剂在不同温度的盐酸溶液中对Q235碳钢的缓蚀性能和吸附规律。结果 在静态失重试验中,室温下,随着IM、IU缓蚀剂的加入,碳钢的腐蚀速率从12.54 mg/(cm2?h)分别降低到5.132、0.145 mg/(cm2?h),IM、IU的缓蚀率分别为59.1%和98.9%。随着温度的升高,缓蚀效率略有下降。极化曲线试验表明,增加两种缓蚀剂的浓度,腐蚀电位负移,阳极电流密度下降明显。交流阻抗的测试显示,随着两种缓蚀剂浓度的增大,拟合参数Rct增大、Cdl减小,证明缓蚀剂在金属表面取代了水,并吸附成膜。研究等温吸附模型发现,两种缓蚀剂分子在碳钢表面的吸附符合Langmuir等温吸附方程,且根据SEM及XPS分析,证明缓蚀剂分子通过N原子与金属形成共价键,在金属表面吸附成膜。结论 咪唑啉和咪唑啉基脲对碳钢均具有缓蚀效果,且咪唑啉基脲的缓蚀效果更优异。两种缓蚀剂均属于混合型缓蚀剂,且以抑制阴极腐蚀反应速率为主。两种咪唑啉化合物在碳钢表面的吸附过程为自发放热过程,其吸附规律遵循Langmuir吸附等温模型,属于单分子层吸附。     

Corrosion behavior of T24, T92, VM12, and AISI 304 steels exposed to KCl–NaCl–K2SO4–Na2SO4 salt mixtures

The corrosion mechanisms of T24, T92, VM12, and AISI 304 steels are studied under the influence of NaCl–KCl, NaCl–Na₂SO₄, and KCl–K₂SO₄ salt mixtures in a dry air atmosphere at 650°C for 15 days. NaCl–KCl was the most aggressive deposit and AISI 304 stainless steel exhibited the highest corrosion resistance. There was no relation between the Cr content of the ferritic steels and their corrosion resistance in NaCl–KCl. In contrast, the resistance of high-Cr steels was better when exposed to NaCl–Na₂SO₄ and KCl–K₂SO₄. The high-Cr and the low-Cr steels were more susceptible to NaCl–Na₂SO₄ and to KCl–K₂SO₄, respectively.