In vitro corrosion resistance of Lotus-type porous Ni-free stainless steels

The corrosion behavior of three kinds of austenitic high nitrogen Lotus-type porous Ni-free stainless steels was examined in acellular simulated body fluid solutions and compared with type AISI 316L stainless steel. The corrosion resistance was evaluated by electrochemical techniques, the analysis of released metal ions was performed by inductively coupled plasma mass spectrometry (ICP-MS) and the cytotoxicity was investigated in a culture of murine osteoblasts cells. Total immunity to localized corrosion in simulated body fluid (SBF) solutions was exhibited by Lotus-type porous Ni-free stainless steels, while Lotus-type porous AISI 316L showed very low pitting corrosion resistance evidenced by pitting corrosion at a very low breakdown potential. Additionally, Lotus-type porous Ni-free stainless steels showed a quite low metal ion release in SBF solutions. Furthermore, cell culture studies showed that the fabricated materials were non-cytotoxic to mouse osteoblasts cell line. On the basis of these results, it can be concluded that the investigated alloys are biocompatible and corrosion resistant and a promising material for biomedical applications.     

Effect of the La alloying addition on the antibacterial capability of 316L stainless steel

316L stainless steel is widely used for fashion jewelry but it can carry a large number of bacteria and cause the potential risk of infection since it has no antimicrobial ability. In this paper, La is used as an alloying addition. The antibacterial capability, corrosion resistance and processability of the La-modified 316L are investigated by microscopic observation, thin-film adhering quantitative bacteriostasis, electrochemical measurement and mechanical test. The investigations reveal that the La-containing 316L exhibits the Hormesis effect against Staphylococcus aureus ATCC 25923 and Escherichia coli DH5α, 0.05 wt.% La stimulates their growth, as La increases, the modified 316L exhibits the improved antibacterial effect. The more amount of La is added, the better antibacterial ability is achieved, and 0.42 wt.% La shows excellent antibacterial efficacy. No more than 0.11 wt.% La addition improves slightly the corrosion resistance in artificial sweat and has no observable impact on the processability of 316L, while a larger La content degrades them. Therefore, the addition of La alone in 316L is difficult to obtain the optimal combination of corrosion resistance, antibacterial capability and processability. In spite of that, 0.15 wt.% La around is inferred to be the trade-off for the best overall performance.     

Electrochemical properties of 316L stainless steel with culturing L929 fibroblasts.

Potentiodynamic polarization and impedance tests were carried out on 316L stainless steel with culturing murine fibroblast L929 cells to elucidate the corrosion behaviour of 316L steel with L929 cells and to understand the electrochemical interface between 316L steel and cells, respectively. Potential step test was carried out on 316L steel with type I collagen coating and culturing L929 cells to compare the effects of collagen and L929 cells. The open-circuit potential of 316L steel slightly shifted in a negative manner and passive current density increased with cells, indicating a decrease in the protective ability of passive oxide film. The pitting potential decreased with cells, indicating a decrease in the pitting corrosion resistance. In addition, a decrease in diffusivity at the interface was indicated from the decrease in the cathodic current density and the increase in the diffusion resistance parameter in the impedance test. The anodic peak current in the potential step test decreased with cells and collagen. Consequently, the corrosion resistance of 316L steel decreases with L929 cells. In addition, collagen coating would provide an environment for anodic reaction similar to that with culturing cells.     

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.     

Effect of Copper and Bronze Addition on Corrosion Resistance of Alloyed 316L Stainless Steel Cladded on Plain Carbon Steel by Powder Metallurgy

A sandwich structure with cladding alloyed 316L stainless steel on plain carbon steel was prepared by means of powder metallurgy (PM) processing. Electrolytic Cu and prealloyed bronze (95Cu wt pct, 5Sn wt pct) were added in different contents up to 15% into the surface cladded 316L layers and the effect of alloying concentrations on the corrosion resistance of the 316L cladding layers was studied. The corrosion performances of the cladding samples were studied by immersion tests and potentio-dynamic anodic polarization tests in H_2S0_4 and FeCl_3 solutions. Both 316L and alloyed 316L surface layers with 1.0 mm depth produced by PM cladding had an effect to improve corrosion resistance in H2SO4 and FeCI3 solutions. Small Cu and bronze addition (4%) had a positive effect in H_2SO_4 and FeCl3 solutions. 4% Cu alloyed 316L surface layer produced by PM cladding showed similar anodic polarization behaviour to the 316L cladding layer in H_2SO_4 and FeCl_3 solutions.     

Advances in DLC coatings by hybrid PSII and PECVD as a barrier to corrosion in simulated body fluid*

In this study, diamond-like carbon (DLC) films were deposited on biomedical AISI316L stainless steel by hybrid plasma source ion implantation (PSII) and plasma-enhanced chemical vapour deposition (PECVD). Potentiodynamic polarization tests and Electrochemical Impedance Spectroscopy (EIS) have been employed to investigate the corrosion performance of different DLC films in Tyrode's simulated body fluid (pH = 7.4). The corrosion resistance of the DLC films by PECVD deteriorated rapidly after 24 h of immersion, but those made by hybrid PSII and PECVD offered more effective barrier for AISI316L stainless steel during 72 h of immersion. The test results demonstrated that the DLC film by hybrid PSII and PECVD possessed less corrosion current density, greater corrosion resistance, and more positive breakdown potential in simulated body fluid.     

Mechanical and corrosion behaviour of powder metallurgy stainless steel based metal matrix composites

Abstract

Stainless steel matrix composites were manufactured using powder metallurgy techniques. Matrixes of AISI 316L stainless steel were reinforced with yttria or alumina particles. Chromium diboride was added in some cases and boron nitride in others to obtain steels with densities close to theoretical, using reactive (liquid phase) sintering techniques. The composites showed very good densification and better hardness than the 316L stainless steel without additions. The 316L steel reinforced with 4 wt-% yttria chromium diboride showed the highest density and strength, with an acceptable corrosion resistance.     

高氮奥氏体不锈钢耐点蚀性能研究

目前产于高氮不锈钢的研究多集中于理论基础、制造工艺和力学性能等方面,有关耐蚀性方面的研究有限。通过循环极化、Mott-Schottky曲线以及电化学阻抗(EIS)等方法,研究了Cr23Mo1N奥氏体不锈钢(高氮钢,HNSS)和316L不锈钢在Cl-溶液中的耐点蚀性能。结果表明:与316L不锈钢相比,高氮钢具有更正的自腐蚀电位,更小的维钝电流密度。阻抗谱表明高氮钢的钝化膜比316L更加稳定,且电荷转移电阻更大。Mott-Schottky曲线表明高氮钢的点缺陷施主浓度比316L不锈钢低一个数量级,钝化膜的绝缘性更好。循环极化曲线表明高氮钢的点蚀敏感性更小,钝化膜的自修复能力更强,耐蚀性能更加优越。     

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。     

FDM型3D打印316L不锈钢试样和La对析出物形貌和分布的影响

使用微米级316L不锈钢粉末和蜡基粘结剂制备热融性喂料，用FDM型金属3D打印方法和工艺3D打印成形目标模型生胚，经过脱脂和烧结成形为最终金属试样。对制备出的金属试样进行性能表征和测试，验证了此种成形方式的可行性，针对试样中析出物的形貌不规则和晶界上的夹杂物，研究了稀土La对析出物的影响。根据生胚脱脂后形成的微孔结构，提出一种液相添加稀土La的方法。结果表明:用FDM型3D打印能制备316L不锈钢试样，用液相添加法可向生胚中添加微量稀土La，质量比为0.3%的LaCl₃能显著改善烧结后试样中析出物的微观形貌和分布。     

Synthesis and electrochemical characterization of porous niobium oxide coated 316L SS for orthopedic applications

Niobium oxide was prepared using sol–gel process and coated on 316L stainless steel (SS) substrate via dip-coating technique. The surface characterization results after a thermal treatment revealed that the coated surface was porous, uniform and well crystalline on the substrate. The corrosion resistance and bioactivity of the porous niobium oxide coated 316L SS in simulated body fluid (SBF) solution was evaluated. The in vitro test revealed a layer of carbonate-containing apatite formation over the coated porous surface. The results indicated that the porous niobium oxide coated 316L SS exhibited a high corrosion resistance and an enhanced biocompatibility in SBF solution.     

20/316L双金属管的腐蚀失效原因分析

随着20/316L双金属管在油气生产中的推广应用,关于内衬316L不锈钢的腐蚀失效问题日益突出,尤其是条件苛刻的酸性集输环境下,目前相关研究不多.利用扫描电镜(SEM)、能谱仪(EDS)等测试手段对20/316L双金属管在含H2S-Cl-的酸性集输环境中出现的腐蚀失效问题进行了系统分析,探讨了腐蚀失效的原因.结果表明:20/316L双金属管腐蚀类型为局部腐蚀,主要分布于内衬管316L的底部.腐蚀失效的主要原因是腐蚀介质中存在高浓度的H2S与Cl-,共同促进了钝化膜的破裂与点蚀的发展.当存在较高浓度的H2S与Cl-时,钝化膜薄弱处与电位较低的非金属夹杂物处易发生钝化膜的破裂与金属基体的快速溶解而成为点蚀源,形成点蚀.     

Functional properties of a spark plasma sintered ultrafine-grained 316L steel

A micrometric austenitic stainless steel 316L powder was densified by spark plasma sintering. The process parameters were varied over wide ranges and the impact of such variations on sintered materials was studied through the characterization of their microstructures, densities, hardness and corrosion resistance. For comparison with the properties of traditionally cast 316L, all these investigations were also systematically carried out on as cast samples. The sintered stainless steel produced this way was highly densified, with grains of a micrometric size and the forming process did not induce any residual strain gradients as shown by transmission electronic microscopy analysis. The investigation of the corresponding mechanical properties reveals an enhancement of hardness up to twice the value measured on one sample of as cast 316L. This result is in good agreement with the Hall–Petch formalism. Additionally, in the matter of corrosion behavior, fully dense samples display an enhanced passive state in chloride media compared to as cast material. Spark plasma sintering appears to be an interesting alternative elaboration way of ultrafine 316L stainless steel giving materials with high stress resistance, without strain gradients through the volume, and promising functional properties concerning corrosion behavior.     

Super austenitic stainless steels — a promising replacement for the currently used type 316L stainless steel as the construction material for flue-gas desulphurization plant

Potentiodynamic anodic cyclic polarization experiments on type 316L stainless steel and 6Mo super austenitic stainless steels were carried out in simulated flue-gas desulphurization (FGD) environment in order to assess the localized corrosion resistance. The pitting corrosion resistance was higher in the case of the super austenitic stainless steel containing 6Mo and a higher amount of nitrogen. The pit-protection potential of these alloys 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 that the super austenitic stainless steels have a little tendency for leaching of metal ions such as iron, chromium and nickel at different impressed potentials. This may be due to surface segregation of nitrogen as CrN, which would, in turn, enrich a chromium and molybdenum mixed oxide film and thus impedes the release of metal ions. The present study indicates that the 6Mo super austenitics can be adopted as a promising replacement for the currently used type 316L stainless steel as the construction material for FGD plants.     

Effect of nitrogen on biocorrosion behavior of high nitrogen nickel-free stainless steel in different simulated body fluids

The aim of this research is to study the biocorrosion behavior of high nitrogen nickel-free stainless steel (HNS) with different nitrogen content, also with comparison to AISI 317L, in three different simulated body fluids. The comparison was focused on the influence of nitrogen in HNS and different protein solutions on the passive behavior using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and capacitance measurements (Mott-Schottky approach). The study revealed that HNS possessed thicker and more protective passive films with increase of nitrogen, which could improve the biocorrosion resistance and biocompatibility after implanted. The passive films behaved as n-type semiconductors and showed a decrease in donor density by nitrogen addition, thus indicating more beneficial for haemocompatibility. The electrochemical behavior recorded in the albumin and fibrinogen solutions revealed protein played an important role in the biocorrosion of HNS, which could result in the breakout of passive films and enhance the corrosion rate by means of chelation.     

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。     

Compatibility of ferritic and duplex stainless steels as implant materials: in vitro corrosion performance

The pitting corrosion, crevice corrosion and accelerated leaching of iron, chromium and nickel of super-ferritic and duplex stainless steels, and for effective comparison the presently used 316L stainless steel, have been studied in an artificial physiological solution (Hank's solution) by the potentiodynamic anodic polarization method. The results of the above studies have shown the new super-ferritic stainless steel to be immune to pitting and crevice corrosion attack. The pitting and crevice corrosion resistances of duplex stainless steel were found to be superior to those of the commonly used type 316L stainless steel implant materials. The accelerated leaching study conducted for the above alloys showed very little tendency for the leaching of metal ions when compared with 316L stainless steel. Thus the present study indicated that super-ferritic and duplex stainless steels can be adopted as implant materials due to their higher pitting and crevice corrosion resistance.     

Corrosion susceptibilities of various metals and alloys in synthetic geothermal brines

The corrosion susceptibilities of various pure metals and alloys were investigated in synthetic geothermal fluids. Rates of corrosion of AISI 1010 steel, types 304 and 316 stainless steels, Monel 400 and nickel were determined at three temperatures (296, 333 and 368 K); and those of the molybdenum, niobium and titanium were determined at 368 K only. Type 304 stainless steel appears to undergo an active-passive transition at a temperature range between 333 and 368 K. In the passive state type 304 steel has essentially the same corrosion rate as type 316. At 368 K the corrosion rate of pure nickel was approximately 2.5 times that of Monel, which in turn was twice that of type 316 stainless steel. The corrosion rates of Mo, Nb and Ti were less than one mdd at the highest experimental temperature.     

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.     

Evaluation of TiO2 coatings obtained using the sol–gel technique on surgical grade type 316L stainless steel in simulated body fluid

Gel titania is the titania which was prepared by hydrolysis of a titanium isopropoxide through a sol–gel process. A film of this titania was coated on surgical grade 316L stainless steel using a sol–gel dipping technique. The densified films at 700 °C in vacuum were characterized by X-ray diffraction and EDXA analysis for its crystallinity and purity. The content of the films were determined by FT–IR spectroscopy. The morphology of the coating was analyzed by SEM. The corrosion behavior of 316L SS samples coated with densified titania films were studied in simulated body fluid Ringer's solution by DC potentiodynamic polarization and AC impedance spectroscopic methods. The corrosion kinetic parameters show a considerable increase in the corrosion resistance for the coated steel samples in comparison to the pristine steel substrates.