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1.
Electrochemical impedance spectroscopy (EIS) of Al‐Zn‐Mg‐Cu alloy in EXCO solution has been investigated. The results show that the impedance spectroscopy of the investigated electrode consists of two capacitive loops in the high and middle frequency domain respectively and an inductive loop in the low frequency domain at the first 30 h of immersion; the inductive arc disappears between 30 h and 60 h while it takes on at the low frequency domain at the last 36 h of the immersion time. A model based on the corrosion mechanism of the aluminum alloy and corroding morphology was proposed and applied to analyze the EIS results. 相似文献
3.
拉应力对7075铝合金的剥蚀及其电化学阻抗谱的影响 总被引：3，自引：0，他引：3
研究了拉应力对双级过时效(121℃/35 h+160/20 h ) 7075铝合金剥蚀的影响及合金在EXCO溶液中的电化学阻抗谱.研究表明,拉应力可显著地促进铝合金剥蚀的发生及发展.浸泡初期,合金电化学阻抗谱由一个高-中频容抗弧及一个中-低频感抗弧组成.合金一旦发生剥蚀,电化学阻抗谱上即出现一个高-中频容抗弧及一个中-低频容抗弧. 相似文献
4.
采用电化学阻抗谱（EIS）和光学显微镜原位观察等方法研究了T6态峰时效的2090 Al-Li合金在EXCO溶液中的剥蚀行为.在浸泡过程中局部腐蚀形态演变经历了4个阶段：点蚀、晶间腐蚀、剥蚀和剥蚀后期.在点蚀阶段形成的以杂质相为局部阴极生成的大蚀孔成为剥蚀引发的中心,剥蚀鼓泡沿大蚀孔边缘生长,直到把表层以下完全穿透.点蚀引发阶段的EIS由一个高频容抗弧和一个中低频感抗弧构成,在点蚀发展阶段感抗弧消失.晶间腐蚀阶段的EIS的容抗部分中很难分辨出腐蚀区域对应的时间常数,剥蚀发展阶段和剥蚀后期的EIS由两个容抗弧构成. 相似文献
5.
In order to evaluate the degree and severity of Al-Mg-Mn-Sc-Zr alloy in exfoliation corrosion（EXCO） solution quickly and nondestructively, electrochemical impedance spectroscopy（EIS） technique was employed. The Al- Mg-Mn-Sc-Zr alloy suffers pitting corrosion in the EXCO solution. During pit incubation, the Nyquist diagram is composed of a depressed capacitive arc at high-mediate frequency and an inductive arc at low frequency. The inductive arc fades with immersion time, and the beginning of pitting corrosion and the appearance of two capacitive arcs have simultaneity. During pit propagation, the Nyquist diagram is composed of two overlapped capacitive arcs. As time goes on, two time constants are more clearly distinguished. The high frequency and low frequency capacitive arc are aroused hy passive surface and new interface, respectively. An equivalent circuit is designed to fit EIS, and the experimental results and the fitted results have good correspondence. The degree and severity of pitting corrosion can be obtained by the features of EIS and comparing the fitted values of parameters at different times. 相似文献
6.
The accumulation process of sulfate reducing bacteria (SRB) biofilms established in anaerobic stagnant batch bioreactors on the surface of carbon steel and the nutrient transport and corrosion products distribution in it were characterized by X‐ray Photoelectron Spectroscopy (XPS). In addition, the corrosion occurrence and development of carbon steel under SRB biofilm was investigated by Electrochemical Impedance Spectroscopy (EIS) in‐situ. The results show that the thickness of SRB biofilms increases exponentially with time in the beginning and after 14 days reaches a maximum. From then on, the accumulation rate decreases to zero. In mature biofilms, SRB dispersed throughout the biofilm. In the inner layer near the substrate, due to the high sulfate‐reducing activity of SRB, corrosion products such S2?, H2S and organic acid are present, which lead to corrosion occurrence and development. In the outer layer of the biofilm SRB can also reduce the SO2?4 to SO2?3 and S2O2?3. This metabolism process enhances the Fe2+ transfer from the inner to the outer side. The activity of SRB in the biofilm plays a key role in the initial corrosion process. 相似文献
7.
Al-Li合金在EXCO溶液中腐蚀的电化学阻抗研究 总被引：10，自引：0，他引：10
研究了T6态峰时效AA2090及AA8090A1—Li合金在EXCO溶液中腐蚀的电化学阻抗持征．结果表明,剥蚀发生之前,AA8090合金电化学阻抗谱由一个压缩的高频容抗弧和一个低频感抗弧组成,且低频感抗成分随浸泡时间延长而减弱并消失;一旦发生剥蚀,其电化学阻抗谱即由一个高频和一个低额两个容抗弧组成．而AA2090合金在较短浸泡时间内由于较大面积蚀孔的产生,其电化学阻抗谱上即出现一个高频及一个低频两个容抗弧．发生剥蚀后,两种合金具有相同的电化学阻抗持征． 相似文献
8.
ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY DURING CORROSION PROCESS OF 8090 Al-Li ALLOY IN EXCO SOLUTION
J.F. Li ) Z.Q. Zheng) C.Y. Tan) S.C. Li) Z Zhang) J.Q. Zhang ) ) College of Materials Science Engineering Central South University Changsha China) Department of Chemistry Zhejiang University Hangzhou China) State Key Laboratory for Corrosion Protection Institute of Metal Research The Chinese Academy of Sciences Shenyang China 《金属学报(英文版)》2004,17(6)
1.IntroductionAl-Li alloys, compared to traditional Al alloys, have more excellent properties, such as lower density, greater elastic modulus and higher specific strength[1,2]. In the near future, they would be widely applied to airplane structures. While, exfoliation, a main kind of localized corrosion, lowers their strength, plasticity and fatigue properties, and also decreases their service life[3, 4]. So investigating their exfoliation would be very important to their application.Usua… 相似文献
9.
The present paper describes an electrochemical method of determining the porosity of thin brass coatings by measuring the rate of change in polarization conductance of the system: brass coating—steel substrate—electrolyte. A theoretical explanation of the electrochemical principle of the method is offered. The influence of different factors of the electroplating process, such as pulse current frequency and the presence of a specific additive in the electrolyte, on the porosity of brass coatings has been investigated.Plating conditions under which coatings have minimum porosity are established. There is a close correlation between porosity parameters obtained by this method and rubber adhesion of brass coatings deposited on steel wires. 相似文献
10.
The corrosion performance of a mild steel (MS) exposed to a 0.5 M HCl solution with various concentrations of Rhodanine (Rh)
was studied by means of anodic and cathodic voltammetric curves, electrochemical impedance spectroscopy (EIS) and linear polarization
resistance (LPR) techniques. Rh makes the corrosion of MS in HCl solution decelerate with the exposure time so as to reach
a protective value of more than 99% in 168 h. The adsorption of Rh molecules on the MS obeys Langmiur adsorption isotherm.
Thermodynamic parameters, adsorption equilibrium constant (K
ads), and standard free energy of adsorption (ΔG
ads
o
) were calculated and discussed. The high inhibition efficiency was discussed in terms of blockading the metal surface by
the Rh molecules strongly adsorbing witch their active centers and thus forming a sufficiently effective protective film.
相似文献
11.
Electrochemical polarization and impedance spectroscopic (EIS) techniques were used to investigate the corrosion behavior of Ti‐5Al‐2Nb‐1Ta alloy in Hanks solution at different immersion periods (0 h, 120 h, 240 h and 360 h). The impedance spectra are fitted using a non‐linear least square (NLLS) fitting procedure. The EIS spectra exhibited a two time constant system, suggesting the formation of two layers on the metal surface. The surface morphology of the alloy has been characterized by SEM and EDAX measurements. 相似文献
12.
13.
The effect of the applied tensile stress on the exfoliation corrosion of 7075‐T6 alloy in EXCO solution has been studied. Electrochemistry Impedance Spectroscopy (EIS), Scanning Electron Microscope (SEM) and optical microscope techniques were used to characterize the initiation and propagation of the exfoliation corrosion (EC) under different applied tensile stress levels. Two equivalent circuit models were developed to fit the EIS data of the initiation and propagation stages of EC according to their corresponding physicochemical properties respectively. The correlation between the characteristics of EIS evolution and the localized corrosion types was established, and a new criteria for detecting the initiation of EC of aluminum alloys was brought forward. The results also showed that the tensile stress accelerates EC by increasing the number of the active sites during its initiation stage. 相似文献
14.
Localized corrosion morphologies of 2195 Al‐Li alloy with various heat treatment in 4.0% NaCl solution (pH 6.5) were investigated, and its corrosion mechanism was studied using a three‐electrode coupling system of α (Al) substituting for the precipitate‐free zone (PFZ), simulated bulk θ′ (Al2Cu) and T1 (Al2CuLi). θ′ acts as cathodic zone in the alloy. At the initial stage, T1 phase is active with respect to θ′ and α (Al), and endures the main anodic current, indicating that anodic dissolution occurs on T1. However, its potential moves to positive direction with immersion time, due to dealloying of Li from T1. As a result, the main anodic dissolution occurs on α (Al) at a later stage. At this stage, as only T1 and α (Al) are coupled, T1 is cathodic to α (Al). In real 2195 alloy, T1 phase is very tiny, and anodic dissolution of T1 and PFZ occurs alternately. These results show that its intergranular corrosion or intersubgranular corrosion is caused by alternate anodic dissolution of T1 phase and PFZ along grain and subgrain boundaries. 相似文献
15.
In this study,ceramic coatings were deposited on 6061 Al alloy using a plasma electrolytic oxidation(PEO)technique,and the effect of concentrations of KOH and Na_2SiO_3 as electrolytes for PEO process was studied on microstructure,chemical composition,and electrochemical behavior of PEO coatings formed on the 6061 Al alloy.The results indicated that the increase in concentration of KOH led to rise in electrical conductivity of electrolyte.Consequently,the breakdown voltage reduced,which in turn improved the surface quality and the corrosion behavior.Moreover,the increase in concentration of Na_2SiO_3 resulted in the increase in incorporation of Si in the coating,which led to a higher corrosion potential in the concentration of 4 g L~(-1).According to this investigation,the best protection behavior of coatings can be obtained when the KOH and Na_2SiO_3 concentrations in PEO electrolyte are equal to 4 g L~(-1). 相似文献
16.
The paints are used extensively in various fields, especially for the protection of the oil installations such as the storage reservoirs of crude oil. Reducing possession cost and applying the new hygiene and security standards imply the necessity to deepen the knowledge of the physico‐chemical processes of ageing coatings in the first stage and their impact on the corrosion of the substrate. The tests have been carried out on a primer, and on painted steel plates completely immersed in a 3% NaCl solution. The survey of the water absorption and the kinetics deterioration of the paints have been achieved especially by means of electrochemical impedance spectroscopy under the test of salt spray. The barrier weakness of the primer paint, due to the existence of two capacitive loops observed on the Nyquist's diagrams has been put in evidence. While the study of the resistance of the complete system by the test accelerated in the salt spray shows that the system of painting presents a good resistance up to 196 hours, which is equivalent to 8 years of exposure. 相似文献
17.
Polyaniline, polypyrrole and their composites have been deposited on mild steel electrode from aqueous oxalic acid solution by using cyclic voltammetry (CV) technique. The resulting coatings were characterized by scanning electron microscopy and EDX analysis. The protective performance against corrosion of these coatings is evaluated by using electrochemical impedance spectroscopy (EIS) technique in corrosive solution (3.5% NaCl). Impedance data indicates a noticeable enhancement of protection against corrosion processes. Also, comparison of polyaniline‐phosphate and polypyrrole‐phosphate coatings indicates better corrosion protection with polyaniline‐phosphate coatings. 相似文献
18.
铝合金剥蚀过程的电化学阻抗谱分析 总被引：2，自引：3，他引：2
研究了轧制态及峰时效8090铝—锂合金、拉应力作用下及无应力作用时双级过时效7075铝合金的剥蚀发展过程，测量并拟合了合金发生剥蚀后的电化学阻抗谱。结果表明：发生剥蚀后，合金电化学阻抗谱由高—中频和中—低频容抗弧组成；可从电化学阻抗谱的拟合参数(变化趋势)得到剥蚀的相关信息。如剥蚀发展速度、剥蚀形貌、剥蚀表层是否脱落等． 相似文献