Reactions of chromium in SO2-containing atmospheres

The morphology and composition of scales formed on unalloyed chromium in atmospheres containing SO₂ at high temperatures have been studied. SEM images show chromium sulfides formed at the metal/scale interface. The results indicate that SO₂ may penetrate the scale as molecules, but the rate of this penetration is low. At 600°C formation of Cr₂(SO₄)₃ is also observed by SEM on the scale surface formed in SO₂+O₂/SO₃ mixtures.     

大气环境中SO_2和H_2S对铜的电化学腐蚀行为比较

采用电化学阻抗谱和极化曲线比较研究了含有SO2或H2S的大气环境中铜电极在液膜中的电化学腐蚀行为。结果显示,随着SO2或H2S含量的增加,铜电极的电荷转移电阻和膜电阻减小,双电层电容和膜电容增大,同时铜电极的腐蚀电位负移,腐蚀电流密度增大,大气中的SO2或H2S可能通过改变铜电极表面腐蚀产物的组成,降低电极反应阻力,促进铜的阳极溶解过程,加速铜的腐蚀。在相同质量浓度下,两种腐蚀性气体中H2S对铜的侵蚀性更大。     

The Atmospheric corrosion of statue bronzes exposed to SO2 and NO2

We report on the atmospheric corrosion of different cast statue bronzes in humid air containing ppb levels of SO₂ and SO₂+NO₂. In addition, copper, tin, zinc, and lead samples were studied in these environments. The samples were exposed to synthetic atmospheres with careful control of pollutant concentrations, relative humidity and flow conditions. Deposition of SO₂ was studied using on-line gas analysis. The weight gain was registered after four weeks exposure, and corrosion products were analysed by Electron Probe Micro Analyser (EPMA), X-ray diffraction (XRD), and Fourier Transform Infrared spectroscopy (FTIR). The synergistic effect of SO₂ and NO₂ was remarkable on all bronze materials examined. The weight gain was correlated to alloy composition. Thus, high zinc and low lead content resulted in the greatest weight gain, while high tin content favoured a low weight increase. Lead exhibited a rapid deposition of SO₂ followed by zinc and copper, while tin was unreactive towards SO₂. There was no measurable indication that microstructure influenced corrosion. The corrosion product morphology found in SO₂+NO₂ environment indicated a localised type of attack. The anodic sites were covered by a tin-rich corrosion product close to the metal. Oxidation of soluble divalent tin by O₂ at the anodic sites to form insoluble SnO₂ – xH₂O, is suggested to explain the corrosion protection afforded by alloying with tin. Tin was enriched in the corrosion products while no lead was found. The zinc/copper relation was higher in the corrosion products than in the alloy composition.     

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.     

Matte Entrainment by SO2 Bubbles in Copper Smelting Slag

JOM - The attachment of copper matte by bubbles in slags, during the copper smelting process, plays a key role in the copper loss. This paper aims to provide an in-depth insight into the copper...     

CO2环境下油酸咪唑啉对X65钢异种金属焊缝电偶腐蚀的抑制作用研究

研究了X65管线钢与316L不锈钢、Inconel 625双金属复合管的异种金属焊缝在CO2环境下的电偶腐蚀行为,以及油酸咪唑啉的缓蚀作用。结果表明,随着电偶电位差的增大,异种金属焊缝的腐蚀速率明显升高,并且都显著高于母材。添加油酸基咪唑啉缓蚀剂能降低异种金属焊缝在CO2环境下的均匀腐蚀速率。但是,当缓蚀剂浓度添加较低时,异种金属焊接试样的碳钢一侧出现了严重的沟槽腐蚀或密集的点蚀坑;进一步增加缓蚀剂浓度才能消除沟槽腐蚀现象。讨论了缓蚀剂对异种金属焊缝电偶腐蚀的抑制机理,该项研究可为异金属焊接接头处的腐蚀防护提供借鉴。     

基于优化随机森林的H2S腐蚀产物类型及腐蚀速率预测

目的研究H2S环境下碳钢腐蚀产物类型及失重腐蚀速率预测模型,为含硫油气田管道腐蚀防护设计与选材提供依据。方法整合H2S腐蚀模拟实验数据,采用随机森林算法对各腐蚀因素重要性进行排序,一方面以腐蚀产物类型为输出量,通过随机森林分类算法建立硫铁腐蚀产物类别预测模型,另一方面以腐蚀速率为输出量,通过随机森林回归算法建立腐蚀速率预测模型,并与其他模型进行比较。运用网格搜索方法对各类算法的超参数进行优选,以提高预测可靠性。结果随机森林算法得出的影响H2S腐蚀产物类型的因素重要性排序为:H2S分压、温度、pH值、实验周期、总压、CO2分压。基于网格搜索优化的随机森林分类模型交叉验证得分超过0.9,f1得分达到0.96,优于其他三种常用分类模型。采用网格搜索优化的随机森林回归模型预测结果与实际值的均方误差为0.86%。相关系数R值为0.979,优于其他两个回归模型。结论网格搜索优化后的随机森林分类、回归模型对含H2S复杂环境下的碳钢腐蚀产物类型及腐蚀速率预测准确性较高,能够为油气田管道腐蚀防护提供参考。     

Morphology Analysis of the Scale Formed on Crofer 22APU Steel in Atmospheres Containing SO2

This work presents the results of a morphology analysis of the scale formed on Crofer 22APU steel at high temperature in atmospheres containing SO₂. The studies of steel oxidation were conducted on pre-oxidised and non-pre-oxidised steel within the temperature range of 700?C900 °C in a mixture of air of a varying SO₂ content and in pure air. In the case of oxidation in pure air it was established that on the surface of the Crofer 22APU a two-layer scale is formed. The outer layer of the scale contains MnCr₂O₄, whereas the inner layer contains Cr₂O₃. The scale formed in the atmosphere containing SO₂ is also comprised of two layers (outer MnCr₂O₄ and inner Cr₂O₃). The analyses were carried out with the use of the ³⁵S isotope. The analyses of the phase composition and morphology of the formed scale were conducted with the use of SEM/EDX and TEM.     

CuNiCrAl合金在H2SO4溶液中的腐蚀行为

借助金相、X射线衍射(XRD)、扫描电镜(SEM/EDX)及X射线荧光光谱仪研究了CuNiCrAl合金在H2SO4溶液中的腐蚀行为.结果表明CuNiCrAl合金在低温H2SO4溶液中,合金中的Cu相较易腐蚀;当H2SO4溶液浓度和温度达到一定值时,合金出现脱铬腐蚀现象,溶液的浓度和温度越高,脱铬倾向越大,且溶液添加NaCl能促进合金的脱铬腐蚀,还对CuNiCrAl合金的脱铬机制进行了探讨.     

铝在含SO2湿润/干燥环境中的腐蚀规律

利用气体腐蚀试验箱、红外光谱和扫描电镜研究了铝在含SO2 的湿润气氛—不含SO2 的干燥气氛循环的加速试验条件下的腐蚀规律。并进行了未加SO2 而其它试验条件相同的对比试验。试验共分别进行 5个周期(12 0h)。随着时间延长 ,SO2 的腐蚀性作用明显加强 ,铝的腐蚀表现出正指数变化规律 ,即铝的腐蚀速率随时间延长不断增加。结果还显示出铝在含SO2 的潮湿环境中很难形成保护性好的Al2 O3 膜 ,铝在此试验环境中的腐蚀产物为Al2 (SO4 ) 3 ·18H2 O。在未加SO2 的对比试验环境中铝的腐蚀轻微 ,5个周期累计质量增加仅为 0 .0 43g/m2 ,腐蚀质量损失明显小于加SO2 时的腐蚀质量损失 ;试样表面仍很光亮。     

电网铜材在含H_2S大气中的腐蚀研究现状

铜材在H2S环境中引起的腐蚀及其所造成的损失已经受到广泛关注。论述了铜在含H2S大气环境中的腐蚀规律、腐蚀机理和腐蚀行为。分析了影响铜在含H2S大气中腐蚀的环境因素,介绍了大气环境腐蚀性的评估方法及腐蚀产物分析手段,并指出了相关的腐蚀防护措施。     

油管钢在CO_2/H_2S环境中的腐蚀产物及腐蚀行为

对CO_2/H_2S环境中常规油管钢的腐蚀产物的已有研究成果进行了归纳分析,结果表明,在100℃附近,CO_2/H_2S共存环境中,油管钢表面形成的FeS膜的保护性优于FeCO_3,对金属腐蚀有抑制作用。总结出了油管钢的两类分压比规律:第一类分压比,体系中的CO_2分压保持不变,逐渐增加H_2S的分压,腐蚀速率会出现极值;第二类分压比,体系中的H_2S分压保持恒定,腐蚀速率会随着CO_2分压的升高而增加。这对于进一步完善CO_2/H_2S腐蚀理论以及油气田合理选择油套管材料均有一定指导意义。     

Formation, Retention, and Loss of the Metals Atmospheric Corrosion Products. 1. The Integral Weight Model of the Products Formed

Changes of the total weight of tested samples, as well as changes in the weight of the retained atmospheric corrosion products, are studied as functions of corrosion losses in different climate zones and different test duration, for carbon steel, zinc, copper, magnesium, aluminum, Д16 and AMЦ alloys, and brass. An experimental mathematical model for integral weight of formed corrosion products is suggested. Climate effects on the change in the weight of corrosion products retained by metals are studied during long-term exposure of plates and wire spirals recommended by the ISO 9226-92 Standard for the monitoring of atmospheric corrosivity.__________Translated from Zashchita Metallov, Vol. 41, No. 4, 2005, pp. 402–416.Original Russian Text Copyright © 2005 by Panchenko, Strekalov.     

镀锌钢板表面有机硅烷钝化膜的耐蚀性研究

通过极化曲线和交流阻抗测试技术,对比研究了镀锌钢板经单-BTESPT溶液处理、经添加铈盐的BTESPT溶液处理、先经y-APS预处理再经添加铈盐的BTESPT溶液处理所得3种有机硅烷钝化膜的耐蚀性.研究发现:有机硅烷成膜过程中添加一定量的铈盐,可通过其形成的三价和四价氧化物,修复单一硅烷膜存在的缺陷,从而提高防护效果;...     

Corrosion phases of structural shapes exposed to the atmosphere

Based on an experimental work exposing structural shapes to Mexico City’s atmosphere, a statistical model defining and relating corrosion phases of such, and based on meteorological information, corrosion speeds and maximum pollutants concentration is shown. Phases of steel structural shapes corrosion are: stabilization of corrosion effect, transition of corrosion effect, meteorology effect, transition of exceeding humidity effect and initial phase or corrosion effect.     

Alternative environmentally friendly coatings for mild steel and electrogalvanized steel to be exposed to atmospheres

The study of new paint systems that are less harmful to the environment and to man than traditional solvent‐borne systems, but have identical anti‐corrosive characteristics, is an issue of great interest at the present time. The authors of this work have taken advantage of the opportunity to use different natural atmospheres in the Ibero‐American region to study the behaviour of new water‐borne, high‐solids and powder paint systems, with and without pre‐treatment. The study has involved coatings exposure in 7 natural atmospheres and different laboratory accelerated tests. It was completed with scanning electron microscopy (SEM) observations, energy dispersive spectrometry (EDS) analysis, and adhesion, water up‐take and electrochemical measurements. It has been concluded that water‐borne acrylic paint systems incorporating primers pigmented with zinc phosphate and others show deficient behaviour in marine atmospheres, but better behaviour in industrial atmospheres. In marine atmospheres, water‐borne epoxy paint systems, including zinc‐rich primers, together with epoxy and epoxy‐polyurethane high‐solids paint systems, present the most efficient anti‐corrosive behaviour. The coatings obtained with epoxy and epoxy‐polyester powder paints only show good behaviour, when applied on an adequate pre‐treatment, in atmospheres of low to medium corrosivity category (C₂‐C₃). Finally, the best correlation was observed between the results of natural exposure in marine atmospheres, salt spray and water up‐take measurements. It was not possible to verify good correlation between natural exposure and prohesion, adhesion and electrochemical tests. The latter are highly sensitive to the chemical nature of coatings, and seem to be significantly more useful when comparing coatings with more identical nature.