8367、904L和316L奥氏体不锈钢的耐点蚀性能研究

为了研究8367、904L和316L奥氏体不锈钢在不同环境下的的耐点蚀性能,采用电化学试验和浸泡腐蚀试验,从点蚀当量、临界点蚀温度、点蚀电位和腐蚀速率等方面进行了分析。结果表明：8367、904L和316L不锈钢在3.5%NaCl溶液中的临界点蚀温度分别为66,50,15℃;随着介质温度的升高,8367的临界点蚀点位无明显变化,904L和316L的临界点蚀点位则逐渐降低,且E_b（8367）>E_b（904L）>E_b（316L）;8367不锈钢在20℃和50℃的4%FeCl₃溶液中均具有较低的腐蚀速率,且随着温度升高,腐蚀速率无明显变化;904L和316L在20℃和50℃的4%FeCl₃溶液中的腐蚀速率均大于8367,且随着温度升高,904L和316L的腐蚀速率大幅度增大。     

碳钢和不锈钢在高温重质油中的腐蚀行为

石油炼厂减二线油中含有少量的环烷酸,当温度高于200 ℃时,其中的环烷酸与高温活性硫的共同作用, 加剧了金属设备的腐蚀.利用高压釜,以减二线重质油为介质进行动态腐蚀失重试验,考察了200～380 ℃内不同剪切速率下油品对Q235A、16Mn、Cr5Mo等三种低合金钢,18-8、304和316L不锈钢材料的腐蚀行为.发现低合金钢在相同温度下,Cr5Mo的腐蚀速率最小,且这33种低合金钢的腐蚀速率均在260 ℃左右出现一个局部极大值;当温度超过300 ℃后,它们的腐蚀速率再次随温度升高而增加;对于不锈钢,其腐蚀速率则随温度升高而单调增加,316L的耐蚀性最好.     

3种合金在80℃H2SO4和H2SO4-HNO3溶液中的腐蚀行为

化工装置常用316L合金、804合金和Hastelloy C合金制造,使用过程中常接触65%～85%H2SO4溶液和65%～85%H2SO4与少量HNO3的混合液。采用静态挂片试验和电化学方法研究了这3种合金在80℃,72%H2SO4溶液和80℃,72%H2SO4+0.1%HNO3混合溶液中的腐蚀行为。结果表明:在80℃,72%H2SO4溶液中,804合金的耐蚀性优于Hastelloy C合金,316L的耐蚀性最差;在80℃,72%H2SO4+0.1%HNO3溶液中,804合金的耐蚀性优于316L,Hastelloy C合金的耐蚀性最差。     

Fe69.9Cr22.6Mo5.7Cu0.6Zr0.1Nb0.8W0.3非晶合金在不同温度含氯溶液中的耐蚀性

为考察铁基非晶合金在不同温度的含氯溶液中的腐蚀性能,采用电弧熔炼结合真空甩带制备了Fe_69.9Cr_22.6Mo_5.7Cu_0.6Zr_0.1Nb_0.8W_0.3非晶条带,并通过动电位极化曲线、阻抗谱和浸泡实验研究了温度对合金在含氯溶液中耐蚀性的影响。结果表明：与316不锈钢相比,合金具有典型的非晶态结构,其耐蚀性显著增加。在25℃的3.5%(质量分数)NaCl溶液中,其自由面的耐蚀性与辊面相当,自腐蚀电流密度分别约为316不锈钢的18.9%、15.7%;在NaCl溶液中具有稳定的钝化特征,但钝化区间ΔE更宽。在45℃的NaCl溶液中,其自由面与辊面之间的耐蚀性差别显著增大,自腐蚀电流密度显著增加,ΔE变化不大。在80℃的37%盐酸中,其腐蚀速率相对于室温增加了2个数量级,但仍远低于316不锈钢2个数量级。温度的升高使非晶合金表面活性质点增加,氯离子的渗透能力增强,腐蚀反应速度加快。     

316L和45N＋双相不锈钢在食品级H3PO4中的腐蚀行为

为了减少盛装食品级磷酸设备的腐蚀,采用失重法、腐蚀电位-时间曲线、扫描电镜研究了316L不锈钢和45N＋双相不锈钢在食品级H3PO4溶液中的腐蚀行为。结果表明：在55℃,85．0％H3P04溶液中,316L不锈钢的腐蚀速率大于45N＋双相不锈钢;45N＋双相不锈钢表面钝化膜形成速度比316L不锈钢的快;45N＋双相不锈钢在H3PO4溶液中具有很好的耐蚀性,受H3PO4浓度的影响较小,耐蚀性优于316L不锈钢;316L不锈钢的耐蚀性随H3PO4浓度的增加先变好后变差。     

新型镍基耐蚀合金在模拟后处理废液中的腐蚀

采用离子溶出法、晶间腐蚀试验等方法,使用金相显微镜、电子探针等仪器研究了新型耐蚀合金在模拟后处理废液中的耐腐蚀性能。结果表明该耐蚀合金为奥氏体组织,在模拟废液中具有优良的耐腐蚀性能,经110℃连续腐蚀实验,发生了均匀腐蚀,未发现点蚀现象。在室温下年腐蚀速率为0.004 mm/a, 110℃工作环境下年腐蚀速率为0.007 mm/a,其焊接试样室温下的年腐蚀速率为0.005 mm/a, 110℃工作环境下年腐蚀速率为0.010 mm/a,均大幅优于现役316L。该新型耐蚀合金可应用于高寿命设计的后处理容器与设备。     

316L不锈钢焊缝的点蚀行为

采用数显恒温水浴锅HH-4静态模拟点腐蚀的试验方法,研究316L奥氏体不锈钢焊缝在不同Cl^-浓度和温度下的三氯化铁溶液中点腐蚀行为,探讨不同的Cl^-浓度和温度变化对焊缝耐蚀性能的影响。结果表明：在三氯化铁溶液中,Cl^-浓度增加、温度升高,316L奥氏体不锈钢焊缝的耐点蚀性能下降,腐蚀速率增加,腐蚀后的表面形貌为不均匀点腐蚀。     

电化学方法研究腐蚀介质对热浸镀Al-Zn-Si-RE合金镀层腐蚀行为的影响

为研究腐蚀介质对热浸镀Al-Zn-Si-RE合金镀层腐蚀行为的影响,利用电位-时间曲线、Tafel曲线和电化学阻抗谱技术研究了合金镀层在不同盐度、温度和pH值的NaCl溶液中的电化学腐蚀行为,利用扫描电子显微镜(SEM)观察不同腐蚀介质下极化测试后合金镀层的腐蚀形貌.结果表明:随着NaCl溶液温度或浓度的提高,热浸镀Al-Zn-Si-RE合金镀层均出现腐蚀电位负移、镀层腐蚀倾向增大、腐蚀速率增加、腐蚀抗力降低的现象;此外,酸性和碱性条件均会加快镀层在NaCl溶液中的腐蚀速率,其中镀层在pH值为11.0的碱性条件下,腐蚀电流最大,阻抗谱容抗弧幅值最小,说明镀层腐蚀速率最快,耐蚀性最差.     

316L不锈钢中添加Al后的抗腐蚀性能

合金中添加Al可提高其抗腐蚀性能.在316L不锈钢中添加不同含量的Al,研究了合成的合金在5%H2SO4中的均匀腐蚀速率和在65%浓HNO3中的晶间腐蚀速率.结果表明:合金均匀腐蚀速率和晶间腐蚀速率均随着Al含量增加先减小后增大;添加2.00%,4.00%Al的合金的均匀腐蚀速率和晶间腐蚀速率较低;添加了Al的合金的晶间腐蚀速率低于未加Al的合金.     

温度对35钢在船舶尾气络合脱硝液中电化学腐蚀行为的影响

为给脱硝系统设备防护提供思路,采用浸泡试验和电化学试验,研究了35钢在不同温度络合脱硝液中的腐蚀速率,并利用扫描电子显微镜(SEM)对不同温度络合脱硝液中形成的腐蚀产物形貌进行分析。结果显示,通过浸泡试验得出35钢的腐蚀速率在1 mm/a以上,且随温度升高逐渐增大;通过扫描电子显微镜观察,30℃时腐蚀产物结构似颗粒状、堆积紧密,当温度升高到50℃时腐蚀产物结构似葵花状、堆积稀疏,且覆盖率较低;在电化学测试中,35钢在30～50℃络合脱硝液中的腐蚀速率随温度升高而增大。     

Failure cases related to material issues in wet-process phosphoric acid plant

The present paper describes three failure cases of metallic components handling wet-process phosphoric acid at ambient temperatures in a phosphate fertilizer plant. All the three cases of failure were related not directly to the corrosive environment rather to wrong selection or inferior quality of materials. In the first case, pipeline of stainless steel 316L failed due to inferior quality of material used in the elbow region. The elbow material was not a low carbon grade stainless steel and was also in heavily sensitized condition which led to intergranular corrosion and intergranular cracking. The other two cases were related to failures of pump sleeves made up of cast alloys equivalent to stainless steel 316 and Hastelloy C-276 respectively. SS 316 showed through-wall pitting and cracking while Hastelloy C-276 had undergone extensive corrosion along the interdendritic boundaries. Both the materials contained high carbon content which led to heavy precipitation of carbides (Cr-rich carbides in SS 316 and Mo-rich carbides in C-276) along inter-dendritic boundaries during solidification of the casting reducing their corrosion resistance. Recommendations to avoid such failures are also suggested.     

Microstructure and Corrosion Resistance of Dissimilar Weld-Joints between Duplex Stainless Steel 2205 and Austenitic Stainless Steel 316L

The microstructure and corrosion resistance of dissimilar weld-joints between stainless steel SAF 2205 and stainless steel AISI 316 L were investigated. Welding was accomplished by different types of welding wires AWS ER 347, AWS ER 316 L and AWS ER 309 L. To verify soundness of welded samples, nondestructive tests were performed. Metallographic samples were prepared from cross-section areas of weldjoints to investigate microstructure of different regions of weld-joints by optical microscopy and scanning electron microscopy. Corrosion resistance of weld-joints was evaluated in NaCl solution by potentiodynamic polarization and electrochemical impedance techniques. In the weld metal AWS ER 347, the brittle sigma phase was created, resulting in the decrease of weld-joint corrosion resistance. According to the results of metallurgical investigations and corrosion tests, welding wire AWS ER 309 L was suitable for welding duplex stainless steel(SAF 2205) to austenitic stainless steel(AISI 316L) by gas tungsten arc welding(GTAW)process.     

Influence of temperature and hydrodynamic conditions on the corrosion behavior of AISI 316L stainless steel in pure and polluted H3PO4: Application of the response surface methodology

Phosphoric acid is mainly produced by the wet acid process, where corrosion problems could be intensified due to the presence of impurities in the phosphate ores. Operating temperatures and flowing conditions aggravate the aforementioned problems. This work studies the influence of temperature (25–60 °C) and hydrodynamic conditions (Reynolds numbers from 1456 to 5066) on the corrosion of AISI 316L stainless steel in pure and polluted phosphoric acid solutions, by means of cyclic potentiodynamic polarization curves in a hydrodynamic circuit. The effect of temperature is the same as that caused by impurities, that is, higher corrosion rates and hindered passivation and repassivation resistance of the alloy. Statistical analysis by means of surface response methodology proved that the effect of temperature on the corrosion parameters of AISI 316L is more influential than the Reynolds number effect. The Reynolds number seems to have no significant influence on the corrosion behavior of stainless steel. Furthermore, the influence of temperature on the corrosion rate is much higher than on the rest of the corrosion parameters analyzed, especially in polluted phosphoric acid solutions. AISI 316L stainless steel has a clear interest for the phosphoric acid industry as a component material of some equipment due to its good corrosion properties at the different temperatures and Reynolds numbers studied even in polluted media.     

热网换热站不锈钢换热板点蚀的临界条件

热网二级换热站一般采用板式换热器,在其使役过程中不锈钢换热板一旦出现腐蚀穿孔,不但影响一次水水质,而且干扰换热器稳定运行,甚至影响居民供热,因此阐明换热板发生点蚀的临界条件对于科学设定水质控制标准和防止点蚀发生具有重要意义。为此,通过材料化学分析、XRD、SEM及电化学测试等方法对这一问题进行研究。结果表明:在65℃条件下,304不锈钢点蚀的临界Cl;浓度为125 mg/L,316L不锈钢点蚀的临界Cl;浓度为230 mg/L;不锈钢表面一旦形成垢层,表面会发生局部酸化,此时不锈钢更容易发生点蚀;运行过程中为了防止不锈钢换热板点蚀,不仅要严格控制循环水中Cl;浓度,还应防止换热板表面结垢或附着腐蚀产物。     

几种超级不锈钢在模拟烟气脱硫环境中的点蚀行为

目前,针对904L,254s Mo和2507等几种主要备选超级不锈钢在烟气脱硫环境中的耐点蚀性能缺乏系统研究。在温度分别为20、40、70℃的死亡绿液溶液中,利用循环伏安曲线和扫描电镜(SEM)法,对316不锈钢和超级不锈钢904L、254s Mo及2507的极化行为和点蚀形貌进行了研究。结果表明:在该环境中,升高温度可降低4种不锈钢表面钝化膜稳定性并提高其点蚀敏感性;在不同温度环境下,316不锈钢均有严重的点蚀现象发生,而254s Mo和2507不锈钢表面均无明显点蚀迹象;在20℃时,904L不锈钢表面无明显点蚀迹象,40℃时,其表面出现典型的点蚀形貌,但点蚀坑尺寸较小,在70℃的高温下,其点蚀坑尺寸明显增大,点蚀损伤严重;254s Mo和2507均适合作烟气脱硫设备材料,而316、904L在该环境中需谨慎使用。     

Localized Corrosion Behavior of 6% Mo Super Austenitic & 316L Stainless Steels in Low pH 3% NaCl Solution

Electrochemical techniques were applied to study the crevice corrosion resistance of two types of stainless steel alloys namely, conventional 316L and 6% Mo super austenitic in acidified 3% NaCI solution at room temperature. Potentiodynamic results showed that 6% Mo alloy possessed a remarkable resistance to crevice corrosion compared with 316L alloy when they are tested in the same solution. The breakdown potential at which passivity broke down for 316L alloy was 0.00 mV (SCE). The corresponding value for 6% Mo alloy could not reach up to the potential value of 700 mV (SCE). 316L alloy suffered extremely from crevice corrosion at room temperature (about 25℃), which indicates that the critical crevice corrosion temperature, below which crevice corrosion does not occur, was lower than the test temperature. For 6% Mo alloy, the critical crevice corrosion temperature was higher than the testing temperature. Electrochemical parameters indicated that 6% Mo alloy exhibited higher crevice corrosion resistance than 316L alloy.     

316L不锈钢表面纳米化后腐蚀性能研究

对表面纳米化和未经表面纳米化处理的316L不锈钢的样品分别进行点蚀实验和应力腐蚀对比实验,在3.5%(质量分数)NaCl水溶液中分别测出它们的极化曲线.结果表明,316L不锈钢表面纳米化后抗点蚀性能下降,抗应力腐蚀性能提高.对应力腐蚀断口的SEM 分析发现,316L不锈钢应力腐蚀断口有明显分区现象,断裂形式为韧性断裂,开裂通道既有穿晶型也有沿晶型.     

植酸对咸水介质中316L不锈钢耐蚀性的影响

滨海区地源热泵中材料耐腐蚀性研究是有效开展利用新能源的基础,具有重要意义。采用动电位极化扫描和电化学阻抗谱方法研究了不同植酸组装浓度和组装时间对316L不锈钢在地下咸水介质中耐蚀性的影响,并探讨了植酸与钼酸钠复配形成的自组装膜对316L不锈钢在地下咸水介质中耐蚀性的影响。结果表明:在Cl-质量浓度为10g/L的NaCl溶液中,随着植酸浓度的增加,316L不锈钢自腐蚀电流密度呈先减小后增大的趋势,自组装膜对316L不锈钢的防护作用先增强后降低;随着自组装时间的延长,植酸自组装膜对316L不锈钢的缓蚀率先上升后下降。在自组装时间为6h、植酸浓度为10mmol/L时形成的自组装膜防护效果最好,缓蚀率达到84.17%。向植酸自组装液中添加钼酸钠后,形成的聚合钼酸根通过络合作用和静电作用使316L不锈钢的耐蚀性降低,说明植酸的复配对提高咸水介质中316L不锈钢的耐蚀性是有选择的。这为咸水地区地源热泵系统中316L不锈钢换热器的防护提供了理论指导。     

基于点蚀的316L不锈钢在酸性气田环境中的适应性评价

国内外酸性气田的开发使腐蚀环境越来越苛刻,为满足气液混输的工艺要求,发展了耐蚀合金/碳钢的双金属复合管技术。316L不锈钢被广泛用于双金属管的内衬,在含H_2S和CO_2环境中腐蚀速率很低,然而在高含Cl-的溶液中,316L不锈钢容易出现点蚀而诱发集输管线失效,为此,就316L不锈钢在酸性气田集输环境中的点蚀进行评述。讨论了影响316L不锈钢点蚀的材质因素,Mn和Fe的硫化物及Mg、Al、Ca的氧化物等两种夹杂物均能促进钝化膜的溶解而引起点蚀;分析了316L不锈钢点蚀的H_2S、CO_2、温度、Cl-浓度和pH值等环境的适应性条件,发现H_2S环境比CO_2环境更容易发生点蚀,H_2S和CO_2对点蚀发生存在协同机制,温度升高、Cl-浓度增加和酸性介质均会增加316L不锈钢点蚀的敏感性。为进一步优化选材原则,需重点加强环境因素的协同机制、环境适应性的边界条件、点蚀发展的动力学以及新的标准研究。     

城市污水作冷却水时影响316L不锈钢耐蚀性的因素

用电化学方法研究了水质中的Cl-、NH4 -N、化学需氧量(COD)和pH值对316L不锈钢耐蚀性的影响.试验表明:在测试水质条件下,Cl-浓度达到300 mg/L时316L不锈钢点蚀电位有明显的下降;NH4 -N浓度的增加使点蚀电位显著降低;COD的增大使钝化电流有所增大;pH值增大到9时使316L不锈钢钝化电流有明显的增加.