ELECTROCHEMICAL MEASUREMENTS FOR MARINE ATMOSPHERIC CORROSION STUDIES USING KELVIN PROBE REFERENCE ELECTRODE

A Kelvin probe was used as reference in this study on electrochemical measurements of a simulatedmarine atmospheric corrosion system (electrode covered by a very thin electrolyte layer). The experimentalsetups for improved measurements proved satisfactory for the conventional steady-state electrochemicalmeasurements in atmospheric studies.

Corrosion Measurements of Reinforcing Steel by Different Electrochemical Techniques

Electrochemical techniques of the corrosion measurements of reinforcing steeI in concrete have been evaluated. These techniques include half-cell potential measurements, impressed voltage method, impressed current method and potentiostatic polarization technique. The results of corrosion behaviour of the steel in both 5%NaCl and 5%MgSO4 show that each electrochemical technique provides some information about the condition of the steel bar or the corrosivity of the environment being evaluated, yet none provides a complete data regarding the corrosion resistance of reinforcing steel in aggressive media

ELECTROCHEMICAL MEASUREMENT OF FLOW PARAMETERS IN DILUTE SOLUTION

A new theoretical method is proposed in the electrochemical measurement to obtain therelationship between flow parameter and the electrode current under the existence of ion migration ef-fect.In this way the measurement of local mass transfer coefficient,wall shear stress and liquid veloc-ity are presented and the experiment results are also described.

ELECTROCHEMICAL MEASUREMENTS OF COMPONENT ACTIVITIES IN METALLURGICAL SLAGS

The up-to-date status of FeO, CaO, SiO2, P2O5, Ti2O3 and Cr2O3 activity measurements in metallurgical slags using electrochemical sensors is outlined. A description of theoretical concepts and practical sensors is presented including their determining features.

Measurement of Concentration Distribution of Electrogenerated Etchant Using an Electrochemical Probe Technique

An electrochemical probe measurement system for detecting an electrogenerated etchant in solution is developed.Concentration distribution of electrogenerated etchant bromine as close as 8 micrometer to the surface of macrodisk is studied quantitatively.

Electrochemical analysis and convection-enhanced mass transfer synergistic effect of MnO_x/Ti membrane electrode for alcohol oxidation

The different electrocatalytic reactors could be constructed for the electrocatalytic oxidation of 2,2,3,3-tetrafluoro-1-propanol(TFP) with two typical MnO_x/Ti electrodes, i.e.the electrocatalytic membrane reactor(ECMR) with the Ti membrane electrode and the electrocatalytic reactor(ECR) with the traditional Ti plate electrode.For the electro-oxidation of TFP, the conversion with membrane electrode(70.1%) in the ECMR was 3.3 and 1.7 times higher than that of the membrane electrode without permeate flow(40.8%) in the ECMR and the plate electrode(21.5%) in the ECR, respectively.Obviously, the pore structure of membrane and convection-enhanced mass transfer in the ECMR dramatically improved the catalytic activity towards the electro-oxidation of TFP.The specific surface area of porous electrode was 2.22 m^2·g^(-1).The surface area of plate electrode was 2.26 cm^2(1.13 cm^2× 2).In addition, the electrochemical results showed that the mass diffusion coefficient of the MnO_x/Ti membrane electrode(1.80 × 10^(-6) cm^2·s^(-1)) could be increased to 6.87 × 10^(-6) cm^2·s^(-1) at the certain flow rate with pump, confirming the lower resistance of mass transfer due to the convection-enhanced mass transfer during the operation of the ECMR.Hence, the porous structure and convection-enhanced mass transfer would improve the electrochemical property of the membrane electrode and the catalytic performance of the ECMR,which could give guideline for the design and application of the porous electrode and electrochemical reactor.

An electrochemical investigation on collectorless flotation of sphalerite in presence of Cu^(2+) ions

The collectorless flotation behaviors of sphalerite in the presence of Cu 2+ ions have been established. The effects of pH, potential and Cu 2+ concentration on the flotation have been studied using a micro flotation cell specially designed, where the potential can be controlled by a potentiostat. The flotation results have shown that the Cu activated sphalerite displays a good collectorless floatability in a pH range of 0～13. The higher potentials can improve the flotation recovery. The surface species formed during the Cu ion activation have been examined using a special electrochemical technique—a composite sphalerite electrode. Zinc deficient sulfide (Zn 1- x Cu x S) and Cu poly sulfide (Cu y+z S y ) species have been determined. They are responsible for the collectorless flotation of sphalerite. In additional, they can improve the conductivity of the sphalerite surface.

Influence of Ga and Hg on microstructure and electrochemical corrosion behavior of Mg alloy anode materials

The effects of Hg and Ga on the electrochemical corrosion behavior of Mg-5%Hg (molar fraction) alloys were investigated by the measurement of polarization curves and galvanostatic test. The microstructure of the alloys and the corroded surface of the specimens were investigated by scanning electron microscopy, X-ray diffractometry and emission spectrum analysis. It can be concluded that the addition of 1%Ga (molar fraction) reduces corrosion current density from 26.98 mA/cm2 to 2.34 mA/cm2; while the addition of 1%Hg (molar fraction) increases corrosion current density. The addition of Ga and Hg both promotes the electrochemical activity of the alloys and the influence of Ga is more effective than Hg. Mg-5%Hg-1%Ga alloy has the best electrochemical activity, showing mean potential of -1.992 V. The activation mechanism of the magnesium alloy produced by Hg and Ga was put forward. Magnesium atoms are dissolved in liquid Hg and Ga to form amalgam and undergo severe oxidation at the amalgam/electrolyte interface.

Hierarchical Co3O4 Microstructures Decorated with Ag and Cu Oxides： Study of Photocatalytic and Electrochemical Properties

Three-dimensional hierarchical Co3O4 microstructures decorated with Ag and Cu oxides were prepared via displacement reaction and subsequent annealing treatment.Photocatalytic properties measurements revealed that the photocatalystic activities of Cu O/Co3O4 composites（Co3O4 microstructures decorated with Cu O）were enhanced while those of Ag2O/Co3O4 composites（Co3O4 microstructures decorated with Ag2O）were reduced,when compared with those of pure hierarchical Co3O4 microstructures toward the degradation of methyl orange.In addition,Cu O/Co3O4 composites exhibited an excellent recyclability ability of photodegradation.The electrochemical properties test indicated that both of the composite oxide electrodes exhibited excellent pseudocapacitive performance with relatively high specific capacitance and good long-term cycling stability.With the increase of the loaded Ag2O and Cu O dosages deposited on the Co3O4 microstructures surface,the specific capacitance values of the composites were increased.Ag2O/Co3O4 composite electrodes showed higher specific capacitance values and better cycling stability than Cu O/Co3O4 composite ones.

Evaluation of Corrosion Stability of Water Soluble Epoxy-Ester Primer through Electrochemical Studies

The corrosion behavior of water borne epoxy-ester primer coatings (10% - 50% PVCs) was evaluated through electrochemical techniques such as polarization and impedance spectroscopic (EIS) measurements. Studies were carried out for a longer duration of exposure extending up to 60 days in aqueous solution of NaCl (5%). Corrosion current (icorr), Corrosion potential (Ecorr), Coating resistance (Rc), Charge transfer resistance (Rct), Coating capacitance (Cc), Double layer capacitance (Cdl), break point frequency (fb), Water uptake (∮), diffusion coefficient (Dw) etc., indicated that 10% - 30% PVC coatings performed well in comparison to higher PVCs. Changes in the electrochemical characteristics were found to occur as a function of exposure time in all cases. The corrosion stability of the coatings were found to be greatly affected by the percentage of PVCs. Studies further indicated that when lower concentration of pigments were available, they remained completely surrounded by the binder;Thus leaving no space for the entry of corrosive agents. From these studies, it was concluded that the water borne paints could replace the conventional coatings, containing organic solvents. Therefore, water soluble epoxy-ester primers have to be employed in paints for developing eco- friendly coatings.

电催化硝酸根还原制氨

在创新教育背景下,以硝酸根电催化还原制氨为反应案例,将科研成果融入到实验教学中。基于学生已掌握的实验技能和基础电化学知识,利用电化学测量技术、核磁共振波谱法、紫外分光光度法等探究催化剂电催化硝酸根还原制氨的性能。通过具体的实验操作,让学生进一步认识电催化的基本原理,掌握基础的电化学测量技术,激发学生对电化学合成的兴趣。本教学实验内容丰富,涉及多学科知识,满足多学科交叉融合发展需求,有利于学生创新发散思维的培养,符合新时代学科教育要求。

从电池管理到电化学数字电源

电源技术的发展对绿色交通、规模化储能、智慧电网等领域具有重要作用。以电化学器件为代表的电化学电源具有反应机理复杂、多物理场、多尺度特性,同时工作过程中表现出强非线性、时变性及空间分布等特点,为电源的管理带来了挑战。本文以动力电池为对象,分别从模型、测量和管理三个方面阐述当前电池管理技术的研究现状及发展趋势,认为局限于本地的管理技术将逐渐走向全局的数字化管控,提出电化学数字电源的概念并诠释其内涵,旨在助力新能源汽车、氢电储能、新型电网、充电基础设施等电化学电源应用场景的发展。

Micro/nanoelectrode-based electrochemical methodology for single cell and organelle analysis

Cells are the basic unit of life.Electrochemical analysis of single cells/organelles is essential for uncovering the molecular mechanisms of physiological and pathological processes that are difficult to elucidate on a larger scale.This paper provides an overview of the commonly used fabrication methods for micro/nanoelectrodes applied in the investigations of single cells/organelles as well as the corresponding electrochemical measurements over the last four years including extracellular measurement,combination of extra and intracellular measurement,intracellular reactive oxygen species and reactive nitrogen species(ROS/RNS)measurement,and isolated organelles measurement.

冷、热轧工艺对S400不锈钢点蚀性能的影响

为了更好地了解轧制成型工艺对不锈钢板材点蚀性能的影响,通过X射线衍射(XRD)、电子显微镜技术和电化学测试方法等研究了冷、热轧S400不锈钢的微观组织演化、碳化物析出和点蚀机理。结果表明,冷、热轧S400不锈钢基体均为铁素体组织,其中冷轧工艺钢(CR-S400)基体为细长变形的铁素体晶粒,热轧工艺钢(HR-S400)的铁素体晶粒呈现等轴晶;在CR-S400和HR-S400中均观察到了富Cr的M23C6碳化物析出,该碳化物引起了CR-S400和HR-S400的点蚀;HR-S400的点蚀电位较低,极化电阻较小,耐腐蚀性较差,这可能归因于在HR-S400中形成的少量马氏体岛组织的出现降低了S400热轧板的耐蚀性。

精细化工设备腐蚀影响因素及防护措施

为了提高精细化工设备的运行效率,减缓腐蚀进程,并延长其使用寿命,室内采用电化学腐蚀实验的方法,评价了不同因素对精细化工设备电化学腐蚀的影响,并针对性地提出了腐蚀防护措施建议。结果表明:随着实验温度增高,工作介质对Q345R钢的腐蚀电位、腐蚀电流密度和腐蚀速率均先增大后减小;氯离子质量浓度越高,腐蚀电位越小,腐蚀电流密度和腐蚀速率越大;工作介质的pH越高,腐蚀电位、腐蚀电流密度和腐蚀速率就越小;氯离子质量浓度和pH对目标精细化工设备电化学腐蚀的影响相对较大。工作介质中加入腐蚀缓蚀剂RFJ-2后能够明显降低Q345R钢的电化学腐蚀速率,当其质量浓度为20 mg·L^(-1)时,可使腐蚀速率降低92.16%,达到了良好的腐蚀防护效果。

Electrochemical measurements used for assessment of corrosion and protection of metallic materials in the field:A critical review

Corrosion degradation is detrimental to metal structures as it shortens their lifetime and leads to huge economic losses and unexpected disasters.Therefore,the detection and monitoring of corrosion degradation is of great importance.Herein,we briefly review the state-of-the-art electrochemical methods,instrumentation(based on virtual instrumentation),and advanced sensor/probes that are used in the field for the assessment of corrosion damage.Typical corrosion monitoring results,some of which have been obtained at Tianjin University in the past 30 years,for metallic materials and organic coating/metal systems in atmospheric,marine,and soil conditions in the field are presented.Detection methods,data analysis,and theoretical and mathematical models regarding each corrosion system are discussed,and the challenges,problems and possible solutions for each case are suggested.Lastly,future developments,such as wireless,intelligent,and automatic electrochemical measurement,that will augment the present electrochemical methods of evaluating corrosion degradation are summarized.

Reliable Remote-Monitoring Electrochemical Potentiostat for Glucose Measurements

Electrochemical methods have been widely used in the chemical and pharmaceutical industries, which require accurate concentration measurements, chemical reaction detections and analyses. The electrochemical potentiostat, the core element in electrochemical instruments, have been discussed as a hot topic addressing the difficulty of applying high-precision constant voltage and picoampere current measurements. Meanwhile, reliable potentiostats are in demand for complicated industrial environments with noises as well as requirements of remotemonitors. This paper describes a potentiostat for industrial glucose measurement that is not only accurate but also fault tolerant to guarantee high reliability in industrial environments. The instrument uses standard industrial communication protocols, proflbus, and a 4-20 mA current loop, for remote control and monitoring. Experimental results show that this design has 0.01% accuracy with 1 mV resolution for voltage applications and 0.01% accuracy with 1 pA resolution for current measurements. The design is also shown to be highly reliable in noisy environments.

聚二甲基二烯丙基氯化铵对碳钢表面缓蚀性能的研究

采用失重法、电化学测量,探讨在不同工艺条件(腐蚀介质、添加浓度、温度、复配比)下,研究了聚二甲基二烯丙基氯化铵(PDMDAAC)环保型缓蚀剂对碳钢Q235的缓蚀性能,得出最佳工艺条件:10℃时,1 mol/L HCl腐蚀介质中,PDMDAAC浓度为0.5 g/L,PDMDAAC与KI质量复配比为1∶2,缓蚀效果最好,最高为95.78%。研究机理表明,其吸附过程符合Langmuir吸附等温线,吸附过程为以化学吸附为主的混合吸附,SEM、XPS结果验证了PDMDAAC可以在碳钢表面形成保护膜,抑制碳钢表面腐蚀。

一种用于原位测量盐酸露点腐蚀的电化学阻抗探针

设计了一种用于原位测量盐酸露点腐蚀的电化学阻抗探针,该探针结构简单且不需要外接参比电极和对电极。在不同pH的盐酸溶液中,通过探针和传统三电极测量结果对比验证了探针测量腐蚀相关参数的准确性,最后将探针用于原位测量盐酸露点腐蚀。结果表明:相比于原位挂片法,探针不仅可快速监测盐酸露点腐蚀的动态变化过程,还可快速获得瞬时腐蚀速率等电化学参数。