低浓度含氯介质中氯离子向局部腐蚀闭塞区内的迁移规律及其对应力腐蚀破裂的影响

The enrichment of chloride anion within the occluded cell （OC） for Type 304 austenitic stainless steel in low chloride concentration solution has been investigated by means of a simulated OC. The influence of the enrichment of chloride anion on stress corrosion crack （SCC） of Type 304 stainless steel has been studied. It was observed that the amount of chloride anion migration was proportional to the charge flowing through the anode. Owning to the effects of enrichment of chloride anion, low chloride concentration solution could induce SCC for Type 304 stainless steel.     

预应变和敏化顺序对304不锈钢晶间腐蚀敏感性的影响

预应变和敏化处理均对304不锈钢晶间腐蚀敏感性有显著的影响,但是两者的先后处理顺序是否对304不锈钢存在影响还有待讨论。利用硫酸-硫酸铜腐蚀试验方法和双环电化学动电位再活化法(DL-EPR),对304不锈钢预应变和敏化处理后的晶间腐蚀敏感性进行试验研究。采用金相显微镜对硫酸-硫酸铜试验后的试样进行微观组织观察,并利用动电位再活化法进行试样敏化度(DOS)的测量。研究结果表明,在预应变程度和敏化温度时间相同的情况下,先预应变后敏化处理的304不锈钢晶间腐蚀敏感性低于先敏化处理后预应变的试样。     

304不锈钢应力腐蚀的临界氯离子浓度

通过慢拉伸实验得出了304不锈钢应力腐蚀敏感性与溶液中Cl-浓度的关系,用扫描电镜对拉伸试样的断口形貌进行了分析,得出了304不锈钢发生应力腐蚀的临界氯离子浓度。采用自行设计的装置对304不锈钢试样施加拉应力,通过恒应变条件下的电化学原位测试研究了304不锈钢钝化膜破裂电位与氯离子浓度的关系。得出导致钝化膜破裂电位突变的Cl-浓度与发生应力腐蚀破裂的临界Cl-浓度是基本一致的结论。     

循环水中304不锈钢发生点蚀的Cl~-浓度阈值研究

采用电化学法研究了循环水中304不锈钢点蚀电位(Eb)、蚀孔深度、蚀孔数量与氯离子浓度的关系。结果表明,常温下304不锈钢的Eb总是随着氯离子浓度的增大而减小,当氯离子质量浓度小于800 mg/L时,增大氯离子浓度易导致点蚀敏感,而大于该值时增大氯离子浓度不会明显增大点蚀倾向;从蚀孔深度和表面蚀孔数量得出的304不锈钢点蚀倾向由大变小的氯离子质量浓度阈值为770 mg/L。     

316L不锈钢在硫酸盐还原菌与铁氧化菌溶液中的腐蚀及电化学行为

1 INTRODUCTION Type 316L stainless steel has good corrosion re- sistance and has been used increasingly for cooling water service in the chemical, petrochemical and power utility industries. However stainless steel is susceptible to localized corrosion by chloride ions and reduced sulfur compounds[1]. The presence of micro- organisms on a metal surface often leads to highly localized damages in the concentration of the electro- lyte constituents, pH and oxygen levels[2]. These mi- croorg…     

304L不锈钢在溴离子作用下的点蚀行为

通有含溴离子氮气的３０４ Ｌ不锈钢管,经一段时期的使用后产生了严重点蚀。通过解剖被蚀钢管,采用金相分析,ＳＥＭ 形貌分析及ＥＤＳ成分分析的方法,对本案例点蚀特征进行研究, 发现：蚀孔形核于晶界,并以蚀孔自身扩张和孔内形成次生蚀孔两种方式生长,且蚀孔内壁产生富Ｃｒ 层。最后,就相关的电化学理论进行了探讨,并推测活化态蚀孔内壁的溶解导致了富Ｃｒ 层的产生,而富Ｃｒ 层的存在则是孔内建立局部活化态,次生蚀孔形核的物质基础。     

不锈钢电化学着色的研究进展

本文综述了不锈钢电化学着色的研究进展,比较分析了不锈钢电化学着色工艺,基于电解液中的含铬量的不同,可以分为高铬、低铬和无铬电化学着色,其中高铬着色工艺比较成熟,但由于六价铬存在对环境污染而限制了其发展,低铬和无铬着色工艺成了不锈钢电化学着色的发展方向。本文为不锈钢电化学着色工艺发展提供了新的思路。     

塑性变形对AISI304不锈钢组织及耐蚀性的影响

AISI304不锈钢分别在加热180 ℃和低温-70 ℃条件下进行拉伸变形。采用透射电镜观测位错分布,利用铁素体测量仪测定马氏体相(铁磁相)含量,并通过电化学滞后技术分别研究它们在50 ℃条件下0.5 mol·L^-1 MgCl₂水溶液中的腐蚀行为.结果表明：加热180 ℃和低温-70 ℃条件下塑性变形均使AISI304不锈钢中位错密度随变形量增大而增加,AISI304不锈钢在-70 ℃条件下塑性变形时部分奥氏体相转变为马氏体相,而在180 ℃条件下塑性变形时不发生马氏体相变;位错密度的增加使AISI304不锈钢钝化膜的击穿电位略微正移,而马氏体相的增加使击穿电位呈负移趋势,材料耐孔蚀性能降低.     

氯离子浓度对16Mn与304不锈钢的电偶腐蚀影响的研究

焊缝因为有异种金属接触,所以会发生电偶腐蚀。温州去昂利用普林斯顿2273电化学工作站中的ZRA零电阻电流计通过正交试验的方法研究了氯离子浓度对16Mn和304不锈钢电偶腐蚀的影响。结果表明16Mn开路电位比304不锈钢低;随着氯离子浓度的增加,16Mn与304不锈钢电偶对的电偶腐蚀效应也越大,其电偶腐蚀程度越大电偶腐蚀越严重。     

Electrochemical pitting behaviour of type 321 stainless steel in sulfide-containing chloride solutions

The pitting behaviour of type 321 stainless steel in sulfide-containing chloride aqueous environments was studied using cyclic potentiodynamic polarization. A well-established correlation between H₂S and Na₂S₂O₃ in the study of corrosion was applied, that is, H₂S was simulated by Na₂S₂O₃. The major factors affecting the pitting corrosion of type 321 stainless steel are the Cl^- concentration, solution pH and temperature. The results clearly indicate that both E_pit and E _pp decrease with increasing Cl^- concentration and temperature, while I _pass is more sensitive to temperature variation. E _pit decreased with decreasing pH in the range 2 < pH < 7.5. The surface morphology and chemistry of the corroded type 321 stainless steel resulting from anodic polarization in 0.01 M S₂O ₃ ^2- -containing Cl^- solution were analysed by XRD, SEM and EPMA. A higher concentration of sulfur was found in the pits, and the dark surface film was mainly composed of FeS and -Fe₂O₃. The results describe the pitting behaviour of type 321 stainless steel in sulfide-containing Cl^- aqueous environments.     

Electrochemical investigations of pitting corrosion behaviour of type UNS S31603 stainless steel in thiosulfate-chloride environment

The pitting corrosion behaviour of type UNS S31603 stainless steel (316L SS) in 0.01, 0.05 and 0.1 M thiosulfate ion (S₂O₃ ^2–) in the absence and presence of various concentrations of chloride ion (Cl^–) was studied using the cyclic potentiodynamic polarization method. The influence of major factors which affect pitting corrosion such as pH and temperature, were also investigated. It was found that both the pitting potential (E _pit) and the repassivation potential (E _rp) decreased with increase in Cl^– concentration and solution temperature and a more pronounced difference in E _pit values for various concentrations of S₂O₃ ^2– in 1.0 M Cl^– was obtained at lower temperatures. The effect of pH on E _pit, E _corr and E _rp values for different concentrations of S₂O₃ ^2– in the presence of 1.0 M Cl^– was also determined.     

DEIS assessment of AISI 304 stainless steel dissolution process in conditions of intergranular corrosion

Results presented in this paper are first that demonstrate instantaneous impedance changes versus reactivation potential detected by means of dynamic electrochemical impedance spectroscopy (DEIS) technique for AISI 304 stainless steel dissolution process proceeding during intergranular corrosion (IG) in 0.5 M SO₄²⁻ + 0.01 M KSCN solution of different pHs. Application of DEIS method made it possible to evaluate dynamic changes of the examined system's impedance in conditions of IG. As a result, controlling stage of the overall rate of AISI 304 SS dissolution process was determined. Moreover, the paper proposes an alternative way of assessment of AISI 304 SS dissolution rate during intergranular corrosion based on approximation to theory of iron dissolution in sulfuric acid medium. Simultaneously, on the basis of the DEIS measurements it was possible to obtain information about the degree of sensitization (DOS) of the examined material. Accordingly, performed researches revealed the advantage of the DEIS technique over the electrochemical potentiokinetic reactivation (EPR) tests when investigating intergranular corrosion process.     

2205双相不锈钢在醋酸环境下的点蚀行为研究

2205双相不锈钢由于其具有良好的力学性能,耐腐蚀性能被广泛地应用石油化工设备和管道用材料和选材设计中。本文主要利用电化学极化曲线及交流阻抗技术研究了22Cr双相不锈钢在醋酸以及氯离子条件下耐点蚀行为。结果表明,22Cr双相不锈钢在醋酸环境下有良好的耐腐蚀性能,由于氯离子的存在,增大了该材料的腐蚀倾向,同时也进一步加大了发生点蚀的几率。     

采用ICP对304不锈钢表面黑色腐蚀物的分析

通过采用ICP对304不锈钢表面黑色腐蚀物的分析,发现黑色腐蚀物具有富Ni、贫Fe、Cr的特征,各金属的含量分别达到：Fe13．55％、Cr23．29％、Ni57．54％。分析了黑色腐蚀物在不同环境下的溶解性,并推测了对碱液质量的影响。     

Passivity and passivity breakdown of 304 stainless steel in alkaline sodium sulphate solutions

The passivity and passivity breakdown of 304 stainless steel were investigated in 0.25 M Na₂SO₄solutions of pH 10. The effect of applied potential and the presence of Cl^– ions in the electrolyte were also studied. Different electrochemical methods such as open circuit potential measurements, polarization techniques and electrochemical impedance spectroscopy (EIS) were used. The results showed that the steel electrode passivates under open circuit conditions and also under potentiostatic control. The rate of passive film thickening under open circuit conditions follows a simple logarithmic law. Addition of Cl^– ion shifts the polarization curves in the active direction and above a critical chloride concentration, [Cl^– ] 0.15 M, pitting corrosion occurs and the pitting potential, E _pit, decreases linearly with the logarithm of [Cl^–]. The addition of sulphate ions to the chloride-containing solutions was found to inhibit the pitting process, and at [SO^2- ₄] 0.25 M, a complete immunity to pitting corrosion was recorded. The impedance measurements provided support for film thickening and film breakdown reactions. An equivalent circuit model which consists of a pure resistor, R , in series with a parallel combination of a pure resistor, R _p, and a constant phase element, Q, was proposed to describe the electrode/electrolyte interface. The passive film thickness was found to increase with applied potential up to a critical value of 0.3 V. At higher voltages, breakdown of the passive film occured.     

Critical pitting and repassivation temperatures for duplex stainless steel in chloride solutions

Both the critical pitting temperature (CPT) and critical repassivation temperature (T_r) for two kinds of duplex stainless steels (DSS, namely UNS S31803 and UNS S32750) were investigated in 1 mol/L NaCl solution using the cyclic thermammetry method. Potentiodynamic anodic polarization technique was employed to validate the cyclic thermammetry technique. In addition, the site of pitting nucleated preferentially on the DSS had been confirmed by scanning electron microscopy (SEM). The results demonstrated that there exhibits a hysteresis loop in cyclic thermammetry curve, revealing that the propagating pits could repassivate during the cooling half-cycle. The CPT and T_r for UNS S31803 were 59.6 °C and 36.5 °C, whilst the CPT and T_r for UNS S32750 were 87.5 °C and 70.5 °C, respectively. Pitting was always observed preferentially in the austenite phase. The results can be partially explained based on the changes in chemical composition of ferrite and austenite phases. Moreover, a semi-quantitative model is proposed to explain the existence of T_r.