氧对2205双相不锈钢抗氢氟酸腐蚀性能的影响

为了明确氢氟酸(HF)溶液中的氧对双相不锈钢(DSS)腐蚀性能的影响,通过动电位极化、电化学阻抗、Mott-Schottky曲线等电化学方法以及浸泡试验,研究了2205DSS在不同溶解氧(DO)含量的氢氟酸溶液中的腐蚀行为,采用金相显微镜观察了腐蚀后的表面形貌。结果表明:随着HF溶液中DO含量从7.8 mg/L下降到1.7mg/L,2205DSS的开路电位逐渐变负,自腐蚀电流密度和维钝电流密度区间逐渐增大,钝化电位区间逐渐减小,钝化膜电阻和电荷转移电阻逐渐变小;随着DO含量的降低,2205DSS表面腐蚀凹坑数量逐渐增多,腐蚀越发严重,这主要是因为氧含量的大小影响了2205DSS表面钝化膜的形成速度和钝化膜的缺陷数量。     

循环冷却水含铁细菌对20碳钢管壁腐蚀行为的影响

目前,有关循环冷却水中铁细菌对常用材料20碳钢管壁的腐蚀性报道较少。采用电化学测试技术和表面分析技术,研究了循环冷却管常用材料20碳钢在有无铁细菌循环冷却水中的腐蚀行为。结果表明:在含铁细菌的水中,20碳钢自腐蚀电流密度先由2.965×10~(-4)A/cm~2减小至1.420×10~(-4)A/cm~2再增大至1.653×10~(-4)A/cm~2,浸泡第10 d自腐蚀电流密度较无菌水中增加了1.3倍;有菌水中20碳钢的极化电阻呈先增大后减小的趋势,浸泡第10 d时的极化电阻比无菌水中小111.56Ω·cm~2,与极化曲线的变化呈相同的趋势;在有菌水中20碳钢表面有一些明显的腐蚀裂缝,较无菌水中严重;循环冷却水中铁细菌的存在导致20碳钢自腐蚀电位减小、自腐蚀电流增大、极化电阻明显减小,明显影响其元素成分的含量,从而加速了腐蚀进程。     

铁氧化菌作用下316L不锈钢点蚀电化学特性的研究

采用电化学测量、交流阻抗技术、扫描电镜观察和能谱分析等实验方法,研究了316L不锈钢在铁氧化菌(IOB)溶液中的腐蚀电化学行为,分析了炼油厂冷却水系统微生物腐蚀的特征及机制,结果表明,在含有IOB溶液中的自腐蚀电位(Ecorr)、点蚀电位(Epit)和极化电阻(Rp)均随浸泡时间的增加呈现出降-升-降的变化趋势;在含有IOB溶液中的腐蚀速率均大于在无菌溶液中;IOB的生长代谢活动及其生物膜的完整性和致密性影响了316L不锈钢表面的腐蚀过程,使不锈钢表面的钝化膜层腐蚀破坏程度增加,加速了316L不锈钢的点蚀.     

用电化学噪声技术研究Q235钢在含氯盐模拟混凝土孔隙液中的腐蚀行为

采用电化学噪声技术(EN)和电化学阻抗谱(EIS)研究了Q235钢在0.5 mol/L NaCl的饱和Ca(OH)₂溶液(SCP)中的腐蚀过程,并对噪声数据进行时域分析与频域分析,对阻抗谱数据进行等效电路分析。采用SEM结合EDS和XRD研究了Q235钢的表面形貌和结构组成。结果表明,Q235钢在SCP溶液中的腐蚀过程可分为钝化膜的形成与破裂阶段(Ⅰ)、亚稳态点蚀阶段(Ⅱ)和Ca²⁺沉积和腐蚀产物形成阶段(Ⅲ)。在(Ⅰ)阶段,电流噪声的波动幅值较小,电流噪声标准偏差S_I、白噪声水平W_I较小、噪声电阻R_n较大;在(Ⅱ)阶段,电流噪声波动幅值较大,S_I、W_I呈现阶跃式增长,R_n显著降低;在(Ⅲ)阶段,电流噪声波动幅值增大到200 nA,S_I、W_I、R_n平稳波动。Q235钢在SCP溶液中腐蚀10 d后在其表面出现Fe₂O₃和弥散分布的CaCO₃晶体,此时阻抗谱中出现类Warburg阻抗,腐蚀反应受电荷转移和O₂扩散的联合控制。     

2种温度下O_2对2205DSS在盐卤介质中点蚀行为的影响

为了探索溶解氧含量对2205DSS钢在盐卤中点蚀行为的影响,在30℃和60℃下分别测试了2205DSS于不同盐卤(充氧、除氧和自然态)中的Tafel曲线和循环伏安曲线,并在60℃进行了浸泡腐蚀试验.结果表明:随着盐卤溶液中溶解氧量的增加,2205DSS的腐蚀电位增大;30℃时,溶液充氧与除氧提高了孔蚀保护电位,60℃时,充氧与除氧则主要改变了点蚀击穿电位;30℃和60℃时溶液除氧和充氧均能提高2205DSS在盐卤介质中的耐点蚀性能,除氧的效果优于充氧.     

Cl~-浓度对硫酸盐还原菌体系中316L不锈钢腐蚀行为的影响

油田采出水中Cl-含量是影响材料微生物腐蚀的重要因素,以往对此研究较少。通过电化学阻抗谱(EIS)、扫描电镜(SEM)、能谱(EDS)及荧光显微镜等研究了Cl-浓度分别为200,150,100,30,6 g/L的模拟油田采出水介质中硫酸盐还原菌(SRB)对316L不锈钢腐蚀行为的影响。结果表明:在30 g/L Cl-时316L不锈钢表面细菌附着量明显高于其他盐度,Cl-浓度高于100 g/L时不锈钢表面基本无细菌附着;在低盐度含SRB介质中,试样电荷转移电阻(Rct)较小,耐腐蚀性能较低;在低盐度下试样表面生物膜疏松多孔,有胞外聚合物、腐蚀产物和代谢产物形成,表面的Fe含量明显低于高盐度介质,而C含量较高,SRB的存在增大了试样的腐蚀溶解速度。     

2205双相不锈钢的抗氢氟酸腐蚀行为

氢氟酸用作烷基化油生产的催化剂时,对烷基化装置中常用的Q235钢具有很强的腐蚀性,2205双相不锈钢有望作为替代品,但目前对氢氟酸介质中2205双相不锈钢腐蚀行为的研究不多。通过浸泡试验,考察了2205双相不锈钢和Q235钢在5%HF溶液中的平均腐蚀速度,借助扫描电镜(SEM)观察了2种材料腐蚀后的表面形貌,通过动电位极化和电化学阻抗方法分析了其腐蚀机理。结果表明:Q235钢在5%HF溶液中阳极过程表现为活性溶解,而2205双相不锈钢在该介质中则出现了较宽的钝化区间和较低的维钝电流密度;2205钢的电荷转移电阻约是Q235钢的183倍,2205钢具有良好的抗氢氟酸腐蚀性能,这与其表面形成的钝化膜有关。     

锌在林格氏液中的体外长期腐蚀降解行为

锌基可降解生物材料与已被广泛研究的生物可降解材料(镁和铁)相比, 具有更合适的生物降解速率, 因而近年来受到了广泛的研究和关注。然而, 锌在模拟体液中的长期腐蚀降解行为尚不明确。本研究采用电化学腐蚀测试、表面化学成分分析及降解模式演变观察相结合的方法, 系统研究了锌在林格氏液中浸泡56 d的腐蚀演化过程。根据电化学结果显示, 锌的腐蚀速率P_i在浸泡过程中基本保持稳定, 约为0.06~0.10 mm/a; 失重法测定腐蚀速率为0.3 mm/a到0.5 mm/a。浸泡过程中生成的腐蚀产物主要为Zn₅(CO₃)₂(OH)₆和CaCO₃, 为较致密的细条花棒状和块状产物层, 且随着浸泡时间延长逐渐累积。去除腐蚀产物后发现, 样品表面出现较严重的局部腐蚀, 且腐蚀沟槽的尺寸随浸泡时间的延长而增大, 浸泡42 d腐蚀沟槽宽约为10 μm。本研究为锌基可降解生物材料后期表面改性及潜在生物医学应用提供了数据积累和研究基础。     

304不锈钢在钻井废弃液中的腐蚀行为

目前针对钻井废弃液中材料的腐蚀研究尚属空白。采用浸泡腐蚀试验、电化学阻抗谱(EIS)、动态极化曲线、扫描电镜(SEM)研究了304不锈钢在钻井废弃液介质中浸泡不同时间后的腐蚀情况。结果表明:浸泡腐蚀初期(5~10 d),试样的腐蚀电流密度显著增加,对应的自腐蚀电位和极化电阻减小,耐腐蚀性能变差;而随着浸泡时间的延长(10~30 d),腐蚀电流密度减小,极化电阻增大,腐蚀减缓;浸泡30~90 d期间,极化电阻、自腐蚀电位显著增加;整个浸泡腐蚀期间试样表面的保护膜层处于生成-破坏-自修复的动态变化中,这使得304不锈钢的耐腐蚀性能较好,浸泡腐蚀90 d后的试样表面生成了较为均匀的保护膜。     

Enhanced resistance of 2205 Cu-bearing duplex stainless steel towards microbiologically influenced corrosion by marine aerobic Pseudomonas aeruginosa biofilms

An antibacterial 2205-Cu duplex stainless steel(DSS)was shown to inhibit the formation and growth of corrosive marine biofilms by direct contact with copper-rich phases and the release of Cu~(2+)ions from the2205-Cu DSS surface.In this work,the microbiologically influenced corrosion(MIC)resistance of 2205-Cu DSS in the presence of the corrosive marine bacterium Pseudomonas aeruginosa was investigated.The addition of copper improved the mechanical properties such as the yield strength,the tensile strength and the hardness of 2205 DSS.Electrochemical test results from linear polarization resistance(LPR),electrochemical impedance spectroscopy(EIS)and critical pitting temperature(CPT)measurements showed that 2205-Cu DSS possessed a larger polarization resistance(R_p),charge transfer resistance(R_(ct))and CPT values,indicating the excellent MIC resistance of 2205-Cu DSS against the corrosive P.aeruginosa biofilm.The live/dead staining results and the SEM images of biofilm confirmed the strong antibacterial ability of 2205-Cu DSS.The largest pit depth of 2205-Cu DSS was considerably smaller than that of 2205 DSS after 14 d in the presence of P.aeruginosa(2.2μm vs 12.5μm).2205-Cu DSS possessed a superior MIC resistance to regular 2205 DSS in the presence of aerobic P.aeruginosa.     

Effect of Cu Addition to 2205 Duplex Stainless Steel on the Resistance against Pitting Corrosion by the Pseudomonas aeruginosa Biofilm

The effect of copper addition to 2205 duplex stainless steel(DSS) on its resistance against pitting corrosion by the Pseudomonas aeruginosa biofilm was investigated using electrochemical and surface analysis techniques. Cu addition decreased the general corrosion resistance, resulting in a higher general corrosion rate in the sterile medium. Because DSS usually has a very small general corrosion rate, its pitting corrosion resistance is far more important. In this work, it was shown that 2205-3%Cu DSS exhibited a much higher pitting corrosion resistance against the P. aeruginosa biofilm compared with the 2205 DSS control, characterized by no significant change in the pitting potential and critical pitting temperature(CPT) values. The strong pitting resistance ability of 2205-3%Cu DSS could be attributed to the copper-rich phases on the surface and the release of copper ions, providing a strong antibacterial ability that inhibited the attachment and growth of the corrosive P. aeruginosa biofilm.     

Theoretical analysis of the measurement of polarisation resistance in reinforced concrete

Polarisation resistance (R_p) technique based on Stern–Geary equation is one of the most widely used methods of measuring corrosion rate of reinforcement in the field. With the aid of a “sensorised guard ring”, this electrochemical technique is claimed to be able to determine corrosion rate (I_corr) within a given measuring area. However, there are three theoretical problems in the application of this technique: (1) the original Stern–Geary equation is applicable in a uniform corrosion system at its corrosion potential, whereas the reinforced concrete structure may be subjected to non-uniform corrosion or strong polarisation by macro-cell galvanic effects or imposed currents; (2) the value of the parameter B in the original Stern–Geary equation has been estimated to fall within the range 25–52 mV. This may not be suitable for all the corrosion cases of reinforced concrete structures; (3) The polarised surface area of steel may theoretically not always be fully confined by the sensorised guard ring when the cover concrete is too thick.

This paper aims at discussing the theoretical problems. A general relationship between the dissolution rate of steel reinforcement and the measured polarisation resistance is deduced under general conditions. The range of B value is also analysed based on all the possible corrosion situations of reinforced concrete. Furthermore, unsatisfactory confinement by sensorised guard ring on a thick cover concrete is demonstrated.     

Fatigue properties of ultrafine grained low carbon steel produced by equal channel angular pressing

Ultrafine grained low carbon (0.15 wt.% C) steel produced by equal channel angular pressing (ECAP) was tested for investigating fatigue properties, including cyclic softening and crack growth rate. Emphasis was placed on investigating the effect of load ratio on the fatigue crack growth rates of ultrafine grained microstructure. The ECAPed steel exhibited cyclic softening. After the first cycle, the tension and compression peak stresses decreased gradually with the number of cycles. Fatigue crack growth resistance and the threshold of ECAPed ultrafine grained steel were lower than that of an as-received coarse grained steel. This was attributed to a less tortuous crack path. The ECAPed steel exhibited slightly higher crack growth rates and a lower ΔK_th with an increase in R ratio. The R ratio effect on growth rates and ΔK_th was basically indistinguishable at a lower load ratio (R>0.3) compared with other alloys, indicating that the contribution of the crack closure vanished. This was explained by the fact that finer grained materials produce a lower opening load P_op due to a relatively less serrated crack path. Consequently, K_min can reach K_op readily with a smaller increment of load ratio. The crack growth rate curve for the ECAPed ultrafine grained steel exhibited a linear extension to the lower growth rate regime than that for the coarse grained as-received steel. This behavior can be explained by a reverse crack tip plastic zone size (r_p) that is always larger than the grain size.     

Biofilm inhibition and corrosion resistance of 2205-Cu duplex stainless steel against acid producing bacterium Acetobacter aceti

Acid producing bacterium Acetobacter aceti causes pitting corrosion of stainless steel(SS).This work investigated the enhanced resistance of 2205-Cu duplex stainless steel(DSS) against biocorrosion by A.aceti in comparison with 2205 DSS using electrochemical and surface analysis techniques.With the addition of Cu to 2205 DSS,biofilms on the 2205-Cu DSS surface were inhibited effectively.The largest pit depth on 2205-Cu DSS surface in the presence of A aceti was 2.6 μm,smaller than 5.5 μm for 2205 DSS surface.The i_(corr) was 0.42±0.03 μA cm~(-2) for 2205-Cu DSS in the biotic medium,which was much lower than that for 2205 DSS(3.69±0.65 μA cm~(-2)).All the results indicated that the A aceti biofilm was considerably inhibited by the release of Cu~(2+) ions from the 2205-Cu DSS matrix,resulting in the mitigation of biocorrosion by A aceti.     

热电耦合对铝/钢连续驱动摩擦焊接头组织的影响机理

采用连续驱动摩擦焊技术焊接纯铝1060/Q235低碳钢异质接头,开展两个周期(30天/60天)热电耦合实验(静载392 N+高温300 ℃+直流60 A),研究热电耦合对铝/钢异质接头焊缝微观组织、力学性能及界面生长的影响。结果表明：原始态接头界面径向金属间化合物(IMCs)层厚度不均匀,中心区域无明显IMCs生成。热电耦合30天后界面中心生成宽度为0.3~0.5 μm且以颗粒状由钢侧向铝侧弥散分布的IMCs层,整体拉伸断裂在铝母材的热力影响区。热电耦合60天后IMCs层与钢侧之间出现腐蚀沟槽,IMCs破碎,钢侧无裂纹产生,铝侧形成大量由IMCs层向铝母材内部扩展的裂纹和孔洞,焊缝及裂纹尖端处成分偏析,整体拉伸断裂在焊缝处。界面腐蚀和失效速率与界面IMCs层的厚度成正比,即v_center＜v_1/2R＜v_2/3R。由于原始态接头界面组织不均匀以及热电耦合实验过程中界面不同位置组织生长速率的差异,使得热电耦合后接头界面2/3R位置出现不同断裂形貌的分界线,2/3R内侧以准解理断裂方式为主,2/3R外侧为韧窝断裂和准解理断裂的综合结果。     

不锈钢在烟气脱硫系统中的腐蚀行为

火电厂烟气脱硫系统的设备腐蚀问题比较严重,选材较为关键.为此,选用304不锈钢和2205双相不锈钢,考察了其在烟气脱硫模拟介质(死亡绿液)中不同温度和不同浸泡时间的腐蚀行为.结果表明:304不锈钢在死亡绿液中随温度变化腐蚀性很敏感,易发生点蚀,不宜用作烟气脱硫装置及其零部件;2205双相不锈钢在烟气脱硫模拟介质中不同温度和时间范围内都有良好的耐蚀性,可用作烟气脱硫装置及其零部件的材料.     

Stress Corrosion Cracking of Welded 2205 Duplex Stainless Steel in Sulfide-containing Caustic Solution

Duplex stainless steel (DSS) grades are used in pulp mills for their superior properties and resistance to general corrosion. However, stress corrosion cracking (SCC) of DSS equipment has been experienced in different pulp mills. The susceptibility of DSS grades to SCC can be mainly attributed to the various heating processes involved during the manufacturing of industrial equipments, especially welding. It is generally understood that heating cycles during welding may affect the dual microstructure (ferrite/austenite ratio) of the steel, making it more prone to cracking in aggressive environments such as chlorides and caustics and further exposure to high temperatures. Welded 2205 DSS failed in white liquor (mainly NaOH + Na₂S) was examined for SCC crack morphology and microstructure. Heat-treated 2205 DSS samples were tested in simulated white liquor to see the effect of microstructure on SCC susceptibility. Austenite is more susceptible to SCC than ferrite, but the SCC susceptibility primarily depends on the composition of the alloy and the chemistry of the exposure environment.     

Inactivation of E. coli and Pseudomonas aeruginosa by electrochloration under bipolar pulsed polarization

This work is devoted to the biocides effects by electrochlorination under a pulsated bipolar polarization (PBP) of low potentials (− 1 V/cm to + 1.6 V/cm). Two working electrodes were used, one in platinum and the other in AISI 430 stainless steel, in two different electrolytes: sterilized distilled water and 0,9N sterilized NaCl solution, contaminated by E. Coli or by Pseudomonas Aeruginosa. The inactivation of these bacteria was established under the action of three biocide treatments: E.F (Electric Field); the combination of E.F and Active Chlorine (A.C) and the combination of E.F, A.C and Ions in Solutions (I.S). The synergistic effect of these treatments leads to a high efficiency in disinfection. The results showed that the total inactivation of the E. Coli stain is reached in half a minute, while that of P. aeruginosa is reached in 20 min. The use of an economic stainless steel electrode allowed us to observe that, for pulsate frequencies higher than 10³ s^− 1, the formation of active chlorine increased whereas the corrosion speed decreased.     

Interaction between austein-ferrite phases on passive performance of 2205 duplex stainless steel

The passive behavior of 2205 duplex stainless steel (DSS) and its individual phases (α-phase, γ-phase) in neutral 3.5% NaCl solution was investigated by various electrochemical methods. The results indicated that galvanic effect between α and γ phases cannot deteriorate local corrosion, but favors the enhancement of the passive film. Under the galvanic effect, the diffusion of the dissolved passive cations would be promoted in a short distance between α and γ zones, leading to modifications of the chemical composition and semiconductive property of the passive film and therefore the enhancement of the corrosion resistance of DSS 2205.