Analysis of electrochemical parameters in time domain during the passive layer cracking occurring on the 304L stainless steel in chlorides solution under tensile stresses

Dynamic electrochemical impedance spectroscopy (DEIS) has been applied for detailed analysis of the passive–active transient region during the passive layer cracking process. The effect of applied potential and tensile stresses on the passive layer rupture of type 304L stainless steel (SS) immersed in 0.5 M NaCl solution at room temperature was examined. This paper presents instantaneous impedance spectra obtained for 304L stainless steel samples at the different potential values that refer to the transition from passive into active state while crack of the passive layer took place. Besides, differential dependencies of electrochemical parameters versus relative elongation have been presented to illustrate the system's dynamics changes.     

不同腐蚀试验的电化学阻抗谱评价

采用电化学阻抗谱分析了环氧涂层的介质浸泡、ASTM-B117盐雾试验、PROHESION循环试验的性能变化。实验结果表明:介质浸泡更侧重考察涂层的屏蔽作用,对环氧-聚酰胺体系酸性电解质更容易导致涂层失效;而盐雾试验更容易导致涂层吸收水分,干湿交替增加了有机涂层吸水能力;划痕试验表明样板在ASTM-B117和PRO-HESION遵循不同的腐蚀机理。     

酸性NaCl溶液中304控氮不锈钢腐蚀过程的声发射特征

采用声发射技术和电化学噪声技术研究了304控氮不锈钢C型环试样在0.5mol·L-1NaCl与1.5mol.L-1H2SO4的混合溶液中,恒载荷情况下的腐蚀过程。分析了腐蚀过程中所产生的声发射信号的振铃数随时间分布情况,以及不同阶段的声发射信号的频谱特征。同时对比分析了声发射检测结果与电化学噪声检测结果。结果表明,声发射检测技术对于304控氮不锈钢在酸性NaCl溶液中所产生的腐蚀声发射信号很敏感,在不同腐蚀阶段中,声发射信号特征差异明显,对于判断不同腐蚀阶段具有指导意义;声发射与电化学噪声测试结果基本一致,将声发射检测与电化学噪声检测结合使用,有助于使现场检测结果更加可靠。     

Electrochemical Impedance Spectroscopy as a tool for materials selection: Water for haemodialysis

The water used in haemodialysis must meet very stringent purity criteria to avoid infections. Mineral salts are removed through inverse osmosis and/or ion exchange membranes down to produce very low conductivity values (<1 μ S cm⁻¹ typically), and organic contaminants are removed through adsorption by activated carbon filters. The insidious development of biofilms at stagnant areas such as pipe joints and wall roughness requires periodic disinfection of pumps and piping circuitry. Because disinfectants are highly oxidant chemicals, they tend to induce localised corrosion in the metallic parts of the system, which in turn creates new potential sites for biofilm development. Thus, the optimal combination of disinfectant and material that is acceptable, limiting biofilm development, must be determined. The following two stainless steels were studied: medical grade austenitic AISI 316L, commonly used, and a duplex austenitic–ferritic SAF 2205, which is a possible replacement material. The following two disinfectants were also employed: sodium hypochlorite and peracetic acid. Both disinfectants were used at dosages in the range typically used in the medical industry. The results show that the SAF 2205 and peracetic acid are the best combination of material and disinfectant because they produce the fastest repassivation kinetics and the smoothest surfaces during the disinfection treatment of all combinations studied. The results are interpreted in terms of morphology and kinetics of development of the passive film.     

304L不锈钢在液态锂铅合金中的表面腐蚀研究

采用挂片法、失重法和扫描电镜分析,开展了结构材料304L不锈钢在液态锂铅合金中表面腐蚀行为的研究。研究结果表明：304L不锈钢中的组分元素,在液态锂铅合金中发生了溶解和质量迁移,这是导致材料腐蚀的主要原因,温度与合金中的氧含量是影响表面腐蚀行为最重要的参数。     

Impedance investigation of passive 304 stainless steel in the pit pre-initiation state

The results of impedance measurements on stainless steel 304L by classical and dynamic electrochemical impedance spectroscopy (DEIS) have been presented. The investigation was focused on a transition of steel from passive state to the initial stage of pit formation. Based on the evolution of electrical parameters of the equivalent circuit it has been stated that the most probable mechanism of pit creation is the film-breaking model.     

氯离子对典型不锈钢材料腐蚀的EIS分析

以Alloy 690、Alloy 600和X80 3种典型的不锈钢材料为研究对象,利用电化学阻抗谱实验得到了3种材料在不同浓度的KCl溶液中的阻抗谱特性。实验表明Alloy 690、Alloy 600和X80的抗氯离子腐蚀性能依次降低,当氯离子含量比较少时,随着氯离子浓度的增加,腐蚀的倾向性逐步增加;但当氯离子含量超过一定值时,继续增加氯离子,腐蚀的倾向性反而会减小。R(QR)(QR)电路能够在各种情况下较好地拟合阻抗谱数据,等效电路拟合后的数据表明:外层氧化膜的电阻相对较小,可能会含有可供溶液离子扩散的通道,具有非理想电容器特征;内层氧化膜的结构对材料的抗腐蚀性能影响明显,内层氧化膜阻值突然变小是由于电子通过费米能级从金属向氧化膜渗透。     

Pitting and stress corrosion cracking behavior in welded austenitic stainless steel

The effect of microstructural changes in 304 austenitic stainless steel induced by the processes of gas tungsten arc welding (GTAW) and laser-beam welding (LBW) on the pitting and stress corrosion cracking (SCC) behaviors was investigated. According to the in situ observations with scanning reference electrode technique (SRET) and the breakdown potentials of the test material with various microstructures, the GTAW process made the weld metal (WM) and heat-affected zone (HAZ) more sensitive to pitting corrosion than base metal (BM), but the LBW process improved the pitting resistance of the WM. In the initiation stage of SCC, the cracks in the BM and HAZ propagated in a transgranular mode. Then, the crack growth mechanism changed gradually into a mixed transgranular + intergranular mode. The cracks in the WM were likely to propagate along the dendritic boundaries. The crack initiation rate, crack initiation lifetime and crack propagation rate indicated that the high-to-low order of SCC resistance is almost the same as that for pitting resistance. High heat-input (and low cooling rate) was likely to induce the segregation of alloying elements and formation of Cr-depleted zones, resulting in the degradation in the corrosion resistance.     

The effect of tensile stresses on aluminium passive layer durability

The effect of applied tensile stresses and anodic polarization on the aluminium A91050 passive layer durability in chlorides solution at room temperature has been investigated by means of dynamic electrochemical impedance spectroscopy (DEIS). Performed researches allowed to determine the electrochemical and mechanical conditions of the examined process. Moreover, the threshold strain value for which the aluminium passive layer cracking process occurred was 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.     

脉冲电沉积Fe-Cr合金镀层性能的研究

从三价铬溶液中脉冲电沉积制得Fe-Cr合金镀层,并对Fe-Cr合金镀层的表面形貌、成分、结构、耐蚀性等进行了分析。结果表明:Fe-Cr合金镀层表面光亮,无孔蚀,其中Cr元素的质量分数为28.62%,晶粒尺寸分布在2~50nm之间;与304不锈钢相比,Fe-Cr合金镀层在5%的H2SO4溶液中的耐蚀性更好。     

CR传输线模型解析AgO-Zn电池阻抗谱

电化学阻抗谱(EIS)是研究电池的重要技术之一,但需要合适的解谱方法才能提取有效信息。本文以文献中Ag-Zn电池的阻抗谱拟合数据为例,说明根据普适性CR传输线模型可得到原作者预言存在却无法证实的结果:存在与电池荷电量(SOC)有直线关系,并在SOC=0.4发生转折的参数。结果还表明这种参数有多个,分别与Ag正极的半导体特征,以及放电过程中控制步骤的变化有关,充分显示了EIS信息丰富的特点。本方法结果客观、具有可操作性,因而有重要的理论意义和应用价值。     

Corrosion of stainless steels covered by exopolymers

After a biologically induced corrosion in a 304 stainless steel tube electrochemical tests were carried out on the affected areas to characterise the nature of attack of the steel covered by the excreted exopolymers. Once the corrosive attack has been developed, the samples were removed from the solution, dried out for 1 month and re-immersed in the same well water which caused the attack. Polarization curves and impedance measurements made on non attacked welds, reference stainless steel and the metal covered by the exopolymer confirm that a reactivation of the corrosion process in previously damaged welded areas is produced. However, the corrosive attack has not been so severe than the initially produced by bacteria and after 28 days of immersion the progress of the attack is probably due to the previous activation of the steel surface rather than the microbiological activity.     

再生器发生应力腐蚀开裂的探讨

针对炼油厂催化装置再生器下部件壁发生开裂的现象，通过分析催化装置近几年原料油田的变化、烟气露点测试结果与现场器壁温度对比，认为这是一种氢应力腐蚀开裂（SCC）。结合氢应力腐蚀特点制定了修复方案，特别是焊前预热、焊后热处理，选择合适的焊条及板材，降低了焊道和热影响区硬度，消除残余应力。并对再生器下部壁采取保温措施，确保再生器下部外壁温高于露点（137℃），使之无法在下部器壁形成水汽冷凝液，有效防止SCC的发生。     

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。     

Investigation of selective corrosion resistance of aged lean duplex stainless steel 2101 by non-destructive electrochemical techniques

Lean duplex stainless steel 2101 (LDX2101) shows wide application potential due to its better corrosion performance and lower cost than traditional 304 austenite steel. This paper investigates the effects of thermal aging treatments at 700 °C for various aging times up to 100 h on the selective corrosion resistance of LDX2101 by two non-destructive electrochemical measurements: double-loop electrochemical potentiokinetic reactivation (DL-EPR) and electrochemical impedance spectroscopy (EIS). The evolution of microstructure was examined by optical microscopy, SEM microscopy and X-ray diffraction techniques (XRD). The results showed that the two applied electrochemical measurements agreed very well. Both methods were able to reveal the relationship between microstructure and selective corrosion resistance, which was related to the formation of chromium- and molybdenum-depleted zones around the precipitates, especially the σ phase, during aging. Nevertheless, more information could be obtained using EIS methods, including the interfacial charge transfer reaction and the corrosion product adsorption process. The results suggest that the susceptibility of the aged alloy to selective corrosion is presumably codetermined by the formation of chromium- and molybdenum-depleted areas, as well as by the replenishment of them, in these areas from the bulk during aging.     

Effect of PgTPhPBr on the electrochemical and corrosion behaviour of 304 stainless steel in H2SO4 solution

Weight-loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements were used to study the inhibition of 304 stainless steel corrosion in 1 M H₂SO₄ at 50 °C by propargyltriphenylphosphonium bromide (PgTPhPBr). The inhibiting effects of propyltriphenylphosphonium bromide (PrTPhPBr) and propargyl alcohol (PA) were also studied for the sake of comparison. For the investigated compounds, Tafel extrapolation in the cathodic region gave a corrosion inhibition efficiency of 98% at 1 × 10^–3 M. Adsorption of both PgTPhPBr and PA was found to follow Frumkin's isotherm while adsorption of PrTPhPBr obeys that of Temkin. In the anodic domain, PgTPhPBr acted as a good passivator. The impedance spectra recorded at the corrosion potential (E _cor) revealed that the charge transfer process in the inhibited and uninhibited states controls corrosion of 304 stainless steel.     

Sensitive Detection of SARS-CoV-2 Variants Using an Electrochemical Impedance Spectroscopy Based Aptasensor

The global pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused a threat to public health and a worldwide crisis. This raised the need for quick, effective, and sensitive detection tools to prevent the rapid transmission rate of the infection. Therefore, this study aimed to develop an electrochemical impedance spectroscopy (EIS)-based aptasensor employing an interdigitated gold electrode (IDE) to detect SARS-CoV-2 Spike (S) glycoprotein and viral particles. This allowed us to sensitively detect SARS-CoV-2 S glycoprotein with a limit of detection (LOD) of 0.4 pg/mL in a buffer solution and to obtain a linear increase for concentrations between 0.2 to 0.8 pg/mL with high specificity. The proposed aptasensor also showed a good sensitivity towards the heat-inactivated SARS-CoV-2 variants in a buffer solution, where the Delta, Wuhan, and Alpha variants were captured at a viral titer of 6.45 ± 0.16 × 10³ TCID₅₀/mL, 6.20 × 10⁴ TCID₅₀/mL, and 5.32 ± 0.13 × 10² TCID₅₀/mL, respectively. Furthermore, the detection of SARS-CoV-2 performed in a spiked human nasal fluid provided an LOD of 6.45 ± 0.16 × 10³ TCID₅₀/mL for the Delta variant in a 50 µL sample and a detection time of less than 25 min. Atomic force microscopy images complemented the EIS results in this study, revealing that the surface roughness of the IDE after each modification step increased, which indicates that the target was successfully captured. This label-free EIS-based aptasensor has promising potential for the rapid detection of SARS-CoV-2 in complex clinical samples.     

0Cr18Ni9不锈钢管件腐蚀开裂原因分析

通过查找相关材质和施工资料及金相与化学元素分析,找出了聚氯乙烯项目试车前和试车过程中0Cr18Ni9不锈钢管件腐蚀开裂的原因：①采购的0Cr18Ni9不锈钢管件不符合设计要求;②试压水不符合要求,氯离子含量超标,且试压水未及时排放;③缺少有效的监督管理。     

Electrochemical polymerization of phenol on 304 stainless steel anodes and subsequent coating structure analysis

Anodic oxidation was carried out using 304 stainless steel anodes in neutral 0.1 mol/L phenol solution with an electrolyte composed of 0.1 mol/L sodium sulfate. This oxidation generated a yellow brown polyphenol coating on the steel anode surface. The reaction conditions discussed in this report relate to the methods of linear scanning, cyclic voltammetry and constant current oxidation. The proper anodic electrode potential for polyphenol deposition was observed to be 1.45 V, with a bath voltage of 2.5 V. The chemical structure of the polyphenol coating was analyzed by infrared spectroscopy and the molecular weight of the soluble part of the coating was detected by gel permeation chromatography. A scanning electron microscope was used to analyze the microstructure of the polyphenol coating, taking advantage of the partial solubility of the polyphenol in tetrahydrofuran. The observed linear and flake-layer modes of the polyphenol coating growth are summarized herein.