哌啶缓蚀作用的原子吸收光谱（AAS）研究II.NaCl介质中30 …

采用恒电位计是电流法研究了３０４不锈钢在０．５ｍｏｌ／ＬＮａＣｌ介质中孔蚀发展过程及缓蚀剂对孔蚀发展的抑制作用，同时用原子吸收光谱（ＡＡＳ）测定合金各组分元素的溶解量，结果表明，３０４不锈钢蚀孔内，铬元素以三价，铁，镍和锰以二价离子形式溶解，缓蚀剂ＰＤ不改变各元素溶解的价态，极化电位对孔蚀自催化效应有显著影响，哌啶对３０４不锈钢的孔蚀发展过程有良好的缓蚀作用，ＰＤ对各合金元素存在“选择性抑制”效应     

哌啶对Cr25铁素体不锈钢在中性NaCl介质中钝化膜破坏的缓蚀作用研究

采用稳态阳极极化曲线、电化学阻抗谱(EIS)方法和恒电位-恒电流(P-G)瞬态响应测试技术研究了有机缓蚀剂哌啶(PD)对Cr25铁素体不锈钢在NaCl介质中钝化膜破坏的抑制作用,以及缓蚀剂浓度和Cl~-浓度对钝化膜稳定性的影响。研究结果表明PD可有效地提高Cr25不锈钢在NaCl介质中的稳定性。得到研究体系的“临界浓度比”PD:Cl~-=1:100～170(摩尔比)。按照竞争吸咐机制,讨论了PD对Cr25的缓蚀作用,并对照PD对304不锈钢的保护作用,分析了PD对这两种不锈钢保护作用的异同。     

哌啶缓蚀作用的原子吸收光谱研究I.304不锈钢,工业纯铁 …

采用原子吸收光谱（ＡＡＳ），恒电位下电流～时间关系和极化曲线测试等方法研究了３０４不锈钢，纯铁，铬和镍四种材料在０．１ｍｏｌ／ＬＨＣｌ中的腐蚀行为及哌啶（ＰＤ）的缓蚀作用，结果表明：ＰＤ可有效地抑制３０４不锈钢在盐酸中的腐蚀，ＰＤ增强Ｃｒ在盐酸中的钝化性能，对铁，镍的腐蚀属阴极型缓蚀剂，在ＡＡＳ测试结果表明，３０４不锈钢的组分元素Ｆｅ，Ｃｒ，Ｎｉ和Ｍｎ在盐酸中分别为＋２，＋３，＋２和＋２价离子问式     

哌啶缓蚀作用的原子吸收光谱(AAS)研究——Ⅱ.NaCl介质中304不锈钢孔蚀发展过程及哌啶的缓蚀作用

采用恒电位计时电流法研究了304不锈钢在0.5mol/L NaCl介质中孔蚀发展过程及缓蚀剂对孔蚀发展的抑制作用,同时用原子吸收光谱(AAS)测定合金各组分元素的溶解量。结果表明:304不锈钢蚀孔内,铬元素以三价,铁、镍和锰以二价离子形式溶解,缓蚀剂PD不改变各元素溶解的价态。极化电位对孔蚀自催化效应有显著影响。哌啶对304不锈钢的孔蚀发展过程有良好的缓蚀作用。PD对各合金元素存在“选择性抑制”效应,降低了各元素的溶解速度,弱化孔蚀自催化效应。PD增强孔内沉积层阻力,促使蚀孔向发展速度较慢的类型转变。根据孔蚀发展动力学模型,讨论了PD的缓蚀机制。     

复杂钝化体系P－G响应特征的研究

采用恒电位－恒电流（Ｐ—Ｇ）瞬志响应技术研究了多层结构钝化膜和存在吸附层钝化膜的复杂钝化体系提出了判断钝化膜多层结构的方法以及表征钝化膜不同层稳定性的特征参数，并建立了描述复杂钝化体系Ｐ—Ｇ响应特征的数学模型．研究了２２０５和３１６Ｌ不锈钢在２．５ｍｏｌ／ＬＨ２ＳＯ４中钝化膜的结构，以及吸附型缓蚀剂哌啶和癸胺对３０４不锈钢在０．５ｍｏｌ／ＬＮａＣｌ介质中孔蚀的抑制作用研究结果证实所建立的模型能很好地反映研究体系的Ｐ—Ｇ响应特征．利用提出的特征参数随极化电位和极化时间的变化关系，有效地分析了钝化膜的生长规律和稳定性，以及缓蚀剂对孔蚀发生与发展过程的抑制作用     

430不锈钢在含Cl^—及CO2体系中的孔蚀行为

用动电位滞后曲线法研究了４３０不锈钢在不同介质条件下的孔蚀特性及行为，并对一些缓蚀剂进行了性能测试。结果表明Ｃｌ＾－浓度升高，能促进４３０不锈钢产生孔蚀；温度也有同样作用。     

哌啶对Cr25铁素体不锈钢在中性NaCl介质中钝化膜破坏的缓…

采用稳态阳极极化曲线，电化学阻抗谱方法和恒电位－恒电流瞬态响应测试技术研究了有机缓蚀剂哌啶对Ｃｒ２５铁素体不锈钢在ＮａＣｌ介质中钝化膜破坏的抑制作用，以及缓蚀剂浓度和Ｃｌ＾－浓度对钝化膜稳定性的影响。     

304 不锈钢在氯化钠介质中点蚀缓蚀剂的研究

目的研究钼酸钠、葡萄糖酸钠及其复配物在氯化钠介质中,对304不锈钢点蚀的缓蚀作用。方法对钼酸钠、葡萄糖酸钠按不同配比进行复配得到不同缓蚀剂,采用极化曲线法分别测试在这几种缓蚀剂存在的条件下,304不锈钢在3.5%(质量分数,后同)NaCl溶液中的点蚀电位。结果单组分的钼酸钠、葡萄糖酸钠对在3.5%NaCl介质中的304不锈钢点蚀有一定的抑制作用,且两种缓蚀剂有明显的协同缓蚀效应。结论当复配缓蚀剂配比为c(钼酸钠)∶c(葡萄糖酸钠)=2∶1时,其缓蚀效果达到最佳,点蚀电位为436 mV。     

表面活性剂与极性有机物的增溶作用及缓蚀机理研究

采用多种电化学测试方法并利用孔蚀实验专用电解池研究了由十二烷基硫酸钠,十二醇和ClO_4~-组成的复合缓蚀剂对氯化钠溶液中304不锈钢孔蚀的抑制作用及机理。结果表明:这几种物质的一定配比能抑制304不锈钢在0.1mol/L NaCI中的孔蚀,在较高浓度NaCl溶液中也表现出良好的缓蚀性能。从表面活性剂与极性有机物增溶作用及无机物的还原性两个方面对复合缓蚀剂的耐孔蚀机理进行了分析讨论。     

盐酸体系不锈钢缓蚀剂的开发

采用失重法和扫描电镜法,测定了五种缓蚀剂对浸没于8%盐酸介质中不锈钢的缓蚀作用,确定了在盐酸体系中对不锈钢具有较好缓蚀性的单组分、二元和三元缓蚀剂配方.实验结果表明:咪唑啉,十六烷基三甲基溴化铵具有较好的缓蚀效果;十六烷基三甲基溴化胺在使用浓度为700 mg/L时,缓蚀率为90.0%;十六烷基三甲基溴化铵与三乙醇胺、咪唑啉及硫脲复配后,缓蚀剂各组分浓度为单组分最佳浓度一半的情况下,缓蚀率分别达到为91.8%、90.8%和89.7%,缓蚀剂的成本得以下降;三元复配缓蚀剂中,咪唑啉-硫脲-乌洛托品和咪唑啉-硫脲-三乙醇胺两种缓蚀剂的缓蚀率均高于90%,且使用成本低,是理想的盐酸体系不锈钢缓蚀剂.扫描电镜图像表明,添加了缓蚀剂的金属表面腐蚀轻微,表面光滑,且不存在明显的点蚀倾向,缓蚀剂对金属表面起到很好的保护作用.     

衣康酸介质中Cl^—和NO3^—对不锈钢点蚀电位的影响

利用动电位法测定３１６Ｌ奥氏体不锈钢和Ｒ１双相不锈钢在Ｃ５Ｈ６Ｏ４－Ｃｌ＾－－ＮＯ３＾－水溶液体系中的阳极极化曲线和点蚀电位,探讨了衣康酸（Ｃ５Ｈ６Ｏ４）介质中Ｃｌ＾－和ＮＯ３＾－对点蚀的影响。结果表明：（１）Ｃｌ＾－浓度［Ｃｌ＾－］的提高导致不锈钢点蚀电位Ｅｂ降低,其关系为Ｅｂ＝ａ－ｂｌｇ［Ｃｌ＾－］。同样条件下,Ｒ１不锈钢的点蚀电位比３１６Ｌ不锈钢高３００￣４００ｍＶ;（２）在含Ｃｌ＾－的衣康     

H2S水溶液中的腐蚀与缓蚀作用机理的研究Ⅳ．碱性硫化物溶液中Cl-对碳钢钝化行为的影响

利用交流阻抗和动电位极化技术,在碱性硫化物溶液中,分别研究了阳极极化电位下Ｃｌ~对低碳钢钝化过程阻抗行为的影响,钝化膜临界孔蚀电位Ｅｂ与Ｃｌ浓度的关系以及临界ＣＩ~浓度随温度的变化．结果表明,在除氧的碱性硫化物溶液中,阳极极化的初期阻抗具有两个时间常数,随极化电位的升高,钝化膜逐步趋于完整;在点蚀的形成过程中,容抗弧半径逐渐变小,当极化电位为－６００ｍＶ时容抗弧半径大幅度下降,并出现低频实部电感性收缩现象;在点蚀形成后的发展阶段,容抗弧半径继续减小,阻抗谱出现两个时间常数的双容抗弧．极化研究结果表明,不同温度下,随介质Ｃｌ~浓度增加,电极表面的钝化倾向降低,临界孔蚀电位随Ｃｌ~浓度增加而线性正移．     

Corrosion of 304 stainless steel exposed to nitric acid-chloride environments

In an effort to examine the combined effect of HNO₃, NaCl, and temperature on the general corrosion behavior of 304 stainless steel (SS), electrochemical studies were performed. The corrosion response of 304 SS was bifurcated: materials were either continuously passive following immersion or spontaneously passivated following a period of active dissolution. Active dissolution was autocatalytic, with the corrosion rate increasing exponentially with time and potential. The period of active corrosion terminated following spontaneous passivation, resulting in a corrosion rate decrease of up to five orders of magnitude. The length of the active corrosion period was strongly dependent on the solution volume-to-surface area ratio. This finding, coupled with other results, suggested that spontaneous passivation arises solely from solution chemistry as opposed to changes in surface oxide composition. Increasing NaCl concentrations promoted pitting, active dissolution upon initial immersion, a smaller potential range for passivity, longer active corrosion periods, larger active anodic charge densities preceding spontaneous passivation, and larger corrosion current and peak current densities. In contrast, intermediate HNO₃ concentrations promoted active dissolution, with continuous passivity noted at HNO₃ concentration extremes. During active corrosion, increased HNO₃ concentrations increased the anodic charge density, corrosion current density, and peak current density. The time required for spontaneous passivation was greatest at intermediate HNO₃ concentrations. Susceptibility to pitting was also greatest at intermediate HNO₃ concentrations: the pit initiation and repassivation potentials decreased with increasing HNO₃ concentration until the HNO₃ concentration exceeded a critical concentration beyond which susceptibility to pitting was entirely eliminated. Increasing solution temperature increased the susceptibility to both pitting and active dissolution.     

Cl离子对 304、316不锈钢临界点蚀温度的影响

采用外加恒定电位下腐蚀电流-温度扫描的方法分别研究了304、316不锈钢在不同浓度NaCl水溶液中的临界点蚀温度.得到了材料临界点蚀温度随Cl-浓度变化的关系曲线.在分析温度与Cl-浓度分别对钝化膜影响的基础上阐述了二者对不锈钢点蚀的综合作用机理.     

Cl~-对高氮不锈钢在0.5mol/L NaOH溶液中腐蚀行为的影响

利用动电位极化曲线、电化学阻抗谱和恒电位极化电流响应曲线对一种高氮不锈钢在含不同浓度Cl~-的0.5mol/L NaOH溶液中的腐蚀行为进行了研究。结果表明:高氮不锈钢在含Cl~-的0.5mol/L NaOH中具有良好的耐蚀性,极化曲线表现出阳极钝化特征,Cl~-浓度对点蚀电位无显著影响,钝化电流密度随Cl~-浓度的增加而增大;当Cl~-浓度增加到1.00mol/L时,高氮不锈钢表面生成的钝化膜呈n型半导体,仍具有良好的保护性,钝化膜的载流子密度随着Cl~-浓度的增加而增大。     

Electrochemical behaviour of stainless steels in media containing iron-oxidizing bacteria (IOB) by corrosion process modeling

Localized corrosion mechanism of stainless steel (SS) types UNS S30403 and UNS 31603 in the presence of iron-oxidizing bacteria Sphaerotilus spp. isolated from rust deposits was studied electrochemically. OCP transient, cyclic anodic and cathodic potentiodynamic polarization curves were measured on steel electrodes through their exposure to 3% NaCl solution supplemented with Sphaerotilus culture. The exposure period was composed of three parts: (a) 5 days incubation of steel electrodes in sterile 3% NaCl solution; (b) addition of 3 days-old Sphaerotilus culture to 3% NaCl at 3:2 v/v ratio with subsequent electrodes exposure for 11 days up to complete sedimentation of ferric oxides and (c) subsequent exposure of electrodes for 14 days in upper and bottom (sediments layer) fractions of the experimental medium. The results revealed an instantaneous gradual shift of the transient potential of both steels towards negative potentials from steady-state value of −0.15 V to −0.35 to −0.42 V (SCE) during the whole exposure interval since IOB culture addition into sterile 3% NaCl solution.No evidence of pitting corrosion was found on SS samples subsequent to their exposure to sterile 3% NaCl solution, though in the presence of IOB culture, numerous pits were revealed on 304 L steels specimens exposed to iron hydroxides sediments layer. Electrochemical characteristics (OCP or corrosion potential - E_CORR, breakdown potential - E_BD, repassivation potential - E_RP, passivation current - i_PASS) periodically measured by cyclic polarization method, allowed monitoring the electrochemical behavior changes of experimental SS and to establish the initiation of pitting corrosion in the presence of IOB, resulting in crevice effect caused by biogenic ferric oxides deposits precipitated on steel surface. Overall, steel 316L demonstrated higher resistance to pitting corrosion compared to 304L.