不锈钢海水潮汐区16年腐蚀行为

在青岛、厦门和榆林3个试验站的潮汐区对5种不锈钢暴露16年，总结其腐蚀行为和规律。在潮汐区暴露的不锈钢受点蚀和缝隙腐蚀破坏。不锈钢在潮汐区暴露1至4年的点蚀速度较大，以后点蚀速度减慢。耐点蚀性能较好的不锈钢，耐缝隙腐蚀性能也较好。不锈钢在潮汐区的腐蚀随暴露地点的海水温度升高而加重。增加Cr含量、添加Mo能明显提高不锈钢在潮汐区的耐蚀性。Ni对提高的耐蚀性有效，但影响效果较小。海生物污损能引起不锈钢的局部腐蚀，它对不锈钢在潮汐区的腐蚀有显著影响。     

C15不锈钢在3.5%NaCl溶液中的耐蚀性

用电化学方法研究了C15不锈钢的点蚀电位和缝隙腐蚀行为。结果表明:在30℃的3.5%NaCl溶液中,C15不锈钢的自腐蚀电位和点蚀电位均高于对比材料316L和1Cr18Ni9Ti不锈钢的;C15不锈钢缝隙试验用试样在施加0.8V(SCE)恒电位条件下不发生腐蚀。     

EB104/EB202涂层对904L不锈钢的防腐蚀效果

通过点蚀试验、缝隙腐蚀试验和盐雾试验,研究了904L不锈钢表面未涂覆、半涂覆和全涂覆EB104/EB202涂层试样在不同含量的FeCl_3溶液中的腐蚀行为。结果表明:随着FeCl_3含量的增加,未涂覆EB104/EB202涂层试样的点蚀程度和缝隙腐蚀程度不断加剧。对于半涂覆EB104/EB202涂层试样,其缝隙区、未涂覆区和涂覆区的腐蚀程度依次降低;缝隙区出现严重的点蚀和缝隙腐蚀,且腐蚀程度也随着FeCl_3含量的增加而加剧。全涂覆EB104/EB202涂层试样具有良好的耐点蚀、缝隙腐蚀和盐雾腐蚀性能。     

不锈钢腐蚀评价技术研究及其应用

为了满足我国不锈钢产品设计、热处理与加工工艺的确定与优化、焊接工艺和焊缝质量评定、服役适用性评价等方面的需求,在实现不锈钢各类局部腐蚀(点蚀、缝隙腐蚀、晶间腐蚀、应力腐蚀)常规评价技术的基础上,建立了超316级别不锈钢腐蚀的系统评价技术。本文介绍的是复旦大学材料科学系近来实现的一批主要技术及其应用实例。包括:(1)临界点蚀温度(CPT)和微蚀坑控制技术两类方法;(2)双相不锈钢固溶处理温度范围中合金元素在两相间分配效果的评价;(3)奥氏体不锈钢电化学动电位再活化(EPR)评价技术在双相不锈钢晶间腐蚀评价中的拓展;(4)中低温处理中的二次相析出规律与对应点蚀、晶间腐蚀敏感性的评定;(5)交流阻抗技术在复杂组织晶间腐蚀敏感性评价中的应用;(6)缝隙腐蚀临界温度测量技术及其应用。     

海洋环境中碳钢和不锈钢螺栓紧固件的腐蚀机制差异研究

通过对碳钢和不锈钢紧固件在海洋环境中的腐蚀特征、腐蚀产物和电偶极化等内容的比较性研究,提出了两种不同的腐蚀机制。对于碳钢紧固件,锈层增加了额外的IR降,削弱了阴极区对阳极缝隙区的极化作用,供氧的差异导致螺纹曝露部位的腐蚀更为严重,腐蚀形式以均匀腐蚀为主。对于不锈钢紧固件,缺氧的环境导致螺纹缝隙部位的钝化膜性能劣化,螺杆曝露区对螺纹缝隙区的电偶极化作用促使缝隙区腐蚀更为严重,腐蚀形式以点蚀为主。针对碳钢和不锈钢紧固件在海洋环境中的不同腐蚀机制,提出了差异化的腐蚀防护技术思路。     

不锈钢闭塞腐蚀电池与腐蚀控制

海水中含有大量的氯化物,在有氯离子存在的条件下不锈钢设备容易发生点蚀、缝隙腐蚀以及应力腐蚀等腐蚀形式,这几种腐蚀形式主要的腐蚀机理为闭塞电池腐蚀。通过对闭塞腐蚀电池机理及防护措施的整理和归纳,为不锈钢设备安装调试和防腐蚀维护提供了一定的理论依据,更好的为材料腐蚀防护工作服务。     

新型海水管系材料HDR双相不锈钢的腐蚀和电化学性能

针对新型海水管系材料HDR双相不锈钢的研制和开发，通过冲刷腐蚀，砂侵蚀以及点蚀和缝隙腐蚀电化学试验，研究了其耐海水腐蚀性能和电化学性能，与TUP，B10，B30的耐蚀性能进行了对比，结果表明，HDR很耐流动海水冲刷腐蚀和砂侵蚀，耐点蚀，缝隙腐蚀性能良好，适合作为海水管系材料。     

经济型耐缝隙腐蚀钛合金

钛在海水等中性氮化物及氧化性酸环境中具有比不锈钢更好的抗点蚀和抗缝隙腐蚀能力,但纯钛用于海水淡化装置中,往往在管/管板接头处发生缝隙腐蚀,特别在温度和介质浓度比较苛刻的条件下,缝隙腐蚀更难以避免.     

铝合金在海洋环境中的腐蚀研究(Ⅲ)--海水飞溅区16年暴露试验总结

获得了10种铝合金在青岛海域海水飞溅区暴露16年的腐蚀结果，总结了它们在飞溅区的腐蚀行为和规律。在飞溅区，铝合金对点蚀、缝隙腐蚀较敏感。L4M在飞溅区的耐点蚀性能较差。LF2Y2、LF3M的耐点蚀性能好于L4M。在10种铝合金中LD2CS的耐点蚀性能最好。180YS、LF21M除点蚀、缝隙腐蚀外还发生层间腐蚀。LY11CZ（BL）、LY12CZ（BL）和LC4CS（BL）的包铝层起着牺牲阳极的作用，基体受到有效保护。铝合金在飞溅区的缝隙腐蚀比点蚀严重。在海水飞溅区暴露的铝合金，开始4年的点蚀速度较快，4年后点蚀速度随时间逐渐减慢。暴露8－16年，铝合金的点蚀深度没有明显加深。     

不锈钢的腐蚀分析

分析了不锈钢应力腐蚀开裂(SCC),点腐蚀、晶间腐蚀,腐蚀疲劳,缝隙腐蚀,以及不锈钢的腐蚀机理。     

Corrosion behaviour of carbon S-phase created on Ni-free biomedical stainless steel

Following the success of forming a carbon S-phase (expanded austenite) surface layer on medical grade Ni-free austenitic stainless steel by DC plasma carburising, the established commercial carburising process Kolsterising® was performed on both Ni-containing (AISI 304) and Ni-free austenitic stainless steels. While the Ni-containing stainless steel responded very well to Kolsterising®, the Ni-free alloy did not. The carbon absorption and the hardness of the Kolsterised® Ni-free alloy are inferior to Kolsterised® AISI 304 Ni-containing stainless steel, however, the hardness of the untreated Ni-free alloy was doubled by Kolsterising®. The response of both Kolsterised® Ni-free and Ni-containing alloys to pitting, crevice corrosion and intergranular corrosion resistance was similar. From this work it can be concluded that the Kolsterised® austenitic stainless steels do not suffer from intergranular corrosion but are susceptible to intragranular pitting when tested in boiling sulphuric acid and copper sulphate solution. It was also observed that Kolsterising® improves significantly the pitting and crevice corrosion resistance of the alloys used in this study.     

Pitting and crevice corrosion of superaustenitic stainless steels

Superaustenites are mainly used in offshore applications, oil production and chemical industry. Most important types of localised corrosion of these steels are pitting and crevice corrosion. Investigated materials were N08028, S31254 and three modified alloys. Chromium content of investigated alloys varied between 20 and 27%, molybdenum between 3.2 and 6.0%, nitrogen between 0.1 and 0.36% and copper between 0 and 1.1%. For means of comparison stainless steel AISI 316L has been included in the study. Pitting and crevice corrosion of these highly corrosion resistant steels has been investigated by use of standardized tests. Critical pitting temperature and critical crevice temperatures were determined according to ASTM G 48, Methods C and D, respectively. Electrochemical measurements for determination of pitting potentials were done according to ASTM G 61 as well as for determination of critical pitting temperatures according to ASTM G 150. Results are presented as function of MARC (Measure of alloying for resistance to corrosion) defined by Speidel since linear correlation coefficients were higher when compared to conventional PREN. Results obtained by different testing methods must not be compared directly. Every test however is sensitive to microstructural defects like precipitations and segregations that decrease corrosion resistance. The higher alloyed a material is, the higher is its tendency to form microstructural defects, and the more difficult is it to reach its theoretical corrosion resistance at given chemical composition.     

In vitro electrochemical investigations of advanced stainless steels for applications as orthopaedic implants

Potentiodynamic anodic polarization experiments on advanced stainless steels (SS), such as nitrogenbearing type 316L and 317L SS, were carried out in Hank’s solution (8 g NaCl, 0.14 g CaCl₂, 0.4 g KC1, 0.35 g NaHCO₃, 1 g glucose, 0.1 g NaH₂PO₄, 0.1 g MgCl₂, 0.06 g Na₂HPO₄ 2H₂O, 0.06 g MgSO₄ 7H₂O/1000 mL) in order to assess the pitting and crevice corrosion resistance. The results showed a significant improvement in the pitting and crevice corrosion resistance than the commonly used type 316L stainless steel implant material. The corrosion resistance was higher in austenitic stainless steels containing higher amounts of nitrogen. The pit-protection potential for nitrogen-bearing stainless steels was more noble than the corrosion potential indicating the higher repassivation tendency of actively growing pits in these alloys. The accelerated leaching study conducted for the above alloys showed very little tendency for leaching of metal ions, such as iron, chromium, and nickel, at different impressed potentials. This may be due to the enrichment of nitrogen and molybdenum at the passive film and metal interface, which could have impeded the releasing of metal ions through passive film.     

Susceptibility of stainless steel alloys to crevice corrosion in ClO2 bleach plants

Stainless steels, including duplex stainless steels, are extensively used for equipment in pulp bleaching plants. One serious corrosion problem in chlorine dioxide bleach plants is crevice corrosion of stainless steels, which is frequently the factor that limits their use in bleach plants. Crevice corrosion susceptibility of alloys depends on various environmental factors including temperature, chemical composition of environment and resulting oxidation potential of system. Upsets in the bleaching process can dramatically change the corrosivity of the bleaching solutions leading to temperatures and chemical concentrations higher than those normally observed in the bleach process. When the environmental limits are exceeded the process equipment made of stainless steel can be severely affected. Environmental limits for crevice corrosion susceptibility of eight stainless steel alloys with PRE numbers ranging from 27 to 55 were determined in chlorine dioxide environments. Alloys used in this study included austenitic, ferritic-austenitic (duplex), and superaustenitic stainless steels. The performance of the different stainless steel alloys mostly followed the PRE numbers for the respective alloys. The 654SMO alloy with the highest PRE number of 55 showed the highest resistance to crevice corrosion in this environment. Under the most aggressive chlorine dioxide bleach plant conditions tested, even alloys Nicr3127 and 654SMO with PRE numbers 51 and 55 respectively were susceptible to crevice corrosion attack. The two factors that seem to contribute the most to crevice corrosion and pitting in the investigated environments are temperature and potential.     

核电厂水池覆面用不锈钢钢板在硼酸水溶液中的点蚀行为

采用电化学方法研究了温度、Cl~-以及SO_4~(2-)含量对不锈钢板S30403、S32101和S32205在硼酸溶液中点蚀行为的影响。结果表明:3种材料的点蚀电位(Eb)和再钝化电位(Er)均随Cl~-含量的升高而降低,S32205不锈钢的点蚀电位和再钝化电位普遍高于S32101和S30403不锈钢的;存在临界温度(约60℃),当温度高于临界温度,S32205不锈钢的点蚀电位大幅降低,再钝化电位的临界温度介于40~60℃;SO_4~(2-)含量对3种材料点蚀电位和再钝化电位的影响不明显。S32205不锈钢的耐点蚀性能优于S32101和S30403不锈钢的,而S32101和S30403不锈钢的耐点蚀性能相当。     

Investigation on Pitting Corrosion of Nickel-Free and Manganese-Alloyed High-Nitrogen Stainless Steels

Pitting corrosion behavior of three kinds of nickel-free and manganese-alloyed high-nitrogen (N) stainless steels (HNSSs) was investigated using electrochemical and immersion testing methods. Type 316L stainless steel (316L SS) was also included for comparison purpose. Both solution-annealed and sensitization-treated steels were examined. The solution-annealed HNSSs showed much better resistance to pitting corrosion than the 316L SS in both neutral and acidic sodium chloride solutions. The addition of molybdenum (Mo) had no further improvement on the pitting corrosion resistance of the solution-annealed HNSSs. The sensitization treatment resulted in significant degradation of the pitting corrosion resistance of the HNSSs, but not for the 316L SS. Typical large size of corrosion pits was observed on the surface of solution-annealed 316L SS, while small and dispersed corrosion pits on the surfaces of solution-annealed HNSSs. The sensitization-treated HNSSs suffered very severe pitting corrosion, accompanying the intergranular attack. The addition of Mo significantly improved the resistance of the sensitization-treated HNSSs to pitting corrosion, particularly in acidic solution. The good resistance of the solution-annealed HNSSs to pitting corrosion could be attributed to the passive film contributed by N, Cr, and Mo. The sensitization treatment degraded the passive film by decreasing anti-corrosion elements and Cr-bearing oxides in the passive film.     

不锈钢在海水飞溅区的腐蚀行为

总结了5种不锈钢在青岛海域飞溅区暴露16年的腐蚀行为和 规律.2Cr13在飞溅区不能维持其表面的钝态,耐蚀性较差.含16%Cr以上的不锈钢在飞 溅区有较好的耐蚀性.1Cr18Ni9Ti、00Cr19Ni10和000Cr18Mo2在飞溅区暴露2～4年间,F179 在1、2年间,点蚀速度较大,此后它们的点蚀深度随时间无明显加深.不锈钢在飞溅区的点 蚀密度随暴露时间增大.增加Cr含量、添加Mo能提高不锈 钢在飞溅区的耐蚀性.     

Enhancing the localised corrosion resistance of 316L stainless steel via FBR-CVD chromising treatment

The resistance of stainless steels to localised corrosion can be adversely affected by environmental and metallurgical heterogeneities existed in complex industrial infrastructures such as seawater desalination plants exposed to aggressive evnironments. It is therefore critical to enhance the localised corrosion resistance and understand the corrosion behaviour of stainless steels in complex and aggressive industrial environmental conditions. In this work, the localised corrosion resistance of chromised stainless steel 316L (SS316L) in simulated seawater desalination systems has been investigated by electrochemical and surface analytical techniques. It has been found that chromising processes have improved the localised corrosion resistance of SS316L by reducing its susceptibility to pitting, crevice, and welding zone corrosion in simulated seawater desalination environments. This increased corrosion resistance has been explained by electrochemical polarisation studies and surface analysis showing that the chromising treatment at 1050°C resulted in a continuous and stable chromium-enriched layer on the SS316L surface.