基于X70钢腐蚀检查片的交流腐蚀安全边界测试探析

以在国内6个城市埋设阴极保护腐蚀检查片开展现场测试为研究手段,结合部分室内腐蚀模拟试验结果,通过试片的阴极保护和干扰参数与腐蚀速率的关联性分析初步建立了交流干扰下埋地管道阴极保护安全边界,结论如下：交流干扰下试片的腐蚀速率随试片面积增大而减小;建立了基于极化电位的交流腐蚀安全边界：控制极化电位位于-0.85～-1.20 V(vs CSE)区间且交流电流密度小于30.0 A/m²或控制极化电位位于-0.95～-1.10 V(vs CSE)区间且交流电流密度小于100.0 A/m²;建立了基于直流电流密度的交流腐蚀安全边界：控制直流电流密度位于0.15～20.00 A/m²区间且交流电流密度小于30.0 A/m²或控制直流电流密度位于0.15～1.08 A/m²区间且交流电流密度小于100.0 A/m²;建立了基于pH值的交流腐蚀安全边界：控制pH值位于10.0～14.0区间且交流电流密度小于30.0 A/m²或控制pH值位于11.3～1...     

交流干扰下管道最佳保护准则探究

为了探究交流干扰下抑制管道发生腐蚀的最佳保护准则,通过试验确定交流干扰下达到最佳保护状态时的阴极保护电位,首先验证经典的-0.85 V[vs饱和硫酸铜参比电极(CSE)]阴极保护电位准则和负向偏移100mV阴极保护准则在交流干扰下是否还具有良好的保护效果;接着探究阴极保护电位对保护效果的影响,确定保护效果较好时保护电位的范围.在此基础上,再结合保护程度和保护效率2个评价指标全面分析,找出最佳保护状态下的阴极保护电位取值.结果表明:存在交流干扰时,经典的-0.85 V(vs CSE)阴极保护电位准则和负向偏移100 mV阴极保护准则已经失效;在-1.20 V(vs CSE)以内,阴极保护电位负向升高,对交流干扰下的腐蚀抑制作用会增强;综合腐蚀速率、保护程度和保护效率3个因素,得到交流电流密度在50 A/m2以内时,建议采用-1.00 V(vs CSE)的保护电位;交流电流密度大于50A/m2时,建议采用-1.10 V(vs CSE)的保护电位.     

应用于微电子机械系统中多孔硅的研究

针对多孔硅在MEMS中作为牺牲层和绝热层的应用,主要研究了电化学腐蚀法制备多孔硅的实验条件与多孔硅深度及其孔隙率间的关系,实验发现电化学腐蚀法制备多孔硅的腐蚀速率在腐蚀前期阶段基本是一定值(电流密度为80mA/cm2时为1.3μm/min,电流密度为40 mA/cm2时为0.4μm/min),但到腐蚀后期阶段随着孔深的增加有所下降.同时发现对于不同的腐蚀电流密度,多孔硅的孔隙率都有随腐蚀时间的延长先增加后降低的趋势,用Beale模型可以很好的解释这一现象.最后,针对多孔硅在制备后易发生龟裂的现象,用拉曼光谱分析了多孔硅的内部应力情况,结果表明随多孔硅孔隙率的上升其内部残余应力有增加的趋势.     

工业水中盘管式设备阴极保护电位分布研究

研究了对于盘管状设备实施外加电流阴极保护时,辅助阳极的安放位置与保护电位的关系;保护电流密度与保护电位的关系。依据实验规律,对实际体系——辽化纤维一厂氨致冷立式蒸发器实施了阴极保护,取得了较为满意的效果。     

重庆市埋地管道的腐蚀环境及阴极保护

对重庆市头玛线天然气埋地管道沿线的土壤进行了测量与分析 ,确定了其土壤环境的腐蚀性。采用单只阳极近距离埋设对阴极实施保护 ,管道全线保护电位稳定 ,保护效果良好。     

电流密度对电沉积制备钽基RuO2·nH2O薄膜形貌的影响

采用直流电沉积的方法研究了阴极电流密度的变化(1mA/cm2、3mA/cm2、5mA/cm2、10mA/cm2)对RuO2·nH2O薄膜附着力和形貌的影响,并探讨了RuO2·nH2O电沉积的机理.采用SEM、能谱仪、XRD对薄膜的形貌、元素、物相分别进行了分析,并用粒度分析仪(DELSA 440SX Analyzer Control)对电沉积液的Zeta电位进行了测试.通过实验可以得出:RuO2·nH2O薄膜厚度随着阴极电流密度的增加而增加,薄膜自然干燥失水后,开裂脱落的倾向随电流密度的增加而增大;当阴极电流密度达到10mA/cm2时,自然干燥后薄膜疏松,附着力差.     

馈电试验在市政燃气管道阴极保护工程的应用

开展了现场馈电试验,通过测量管网的管/地自然电位、管/地极化电位、地床电位梯度、接地电阻以及非保护区管线电位变化情况,确定了阴极保护所需的电流密度为10 mA/m^2。试验结果验证了该市使用深井阳极技术对燃气管道阴极保护的安全性、科学性和可行性。     

熔盐电沉积法制备Ni-W功能梯度材料的研究

在NaCl-KCl-NaF-WO3熔盐体系中,采用脉冲电流,700℃的熔盐温度,50mA/cm2的电流密度,沉积10min制备致密Ni-W功能梯度材料(FGM),研究了熔盐组成和电流密度等因素对沉积层表面形貌和厚度的影响规律;并对试样成分和断面形貌进行了分析。结果表明,熔盐组成摩尔比为n(NaCl)∶n(KCl)∶n(NaF)∶n(WO3)=0.3385∶0.3385∶0.25∶0.073,电流密度为50mA/cm2时,可以得到致密、均匀、且具有一定的金属光泽的Ni-W沉积层。     

MgO纳米线的制备及其电子发射性能的研究

采用碳热还原-氧化法成功制备大小均匀的MgO纳米线,采用场致发射电子显微镜(FESEM)和X射线衍射(XRD)表征其形貌及晶体结构。采用丝网印刷将MgO纳米线转移到阴极电极,并将阴极电极与印刷有荧光粉的阳极电极组装成二级场致发射器件。场致电子发射测试表明MgO纳米线具有较好的电子发射特性:其阈值电场强度仅为3.82V/μm(1mA/cm2),最高电流密度达到2.68mA/cm2(4.01V/μm),发光亮度为1152cd/m2,4h内没有明显的衰减。MgO有望作为冷阴极材料在场致发射器件上得到应用。     

洪湖-荆门原油输送管道腐蚀调查评估

按照SY/T0087-95《钢质管道及储罐腐蚀与防护调查方法标准》,对洪湖-荆门原油输送管道进行了腐蚀调查评估,并采用PCM埋地管道电流测绘系统、C扫描埋地管线防腐蚀检测系统、变频-选频法3种目前典型的测量仪器和技术分别测试了管道防腐蚀层的绝缘电阻Rg,确定了管道防腐蚀层缺陷的位置,从而对阴极保护系统的运行现状进行了评估,并提出改进意见和防腐蚀对策.     

Factors affecting cathodic-protection interference

A 3D theoretical simulation and analysis of DC stray-current corrosion (SCC) is introduced. The use of boundary element analysis system (BEASY) has allowed cathodic protection (CP) interference to be assessed in terms of the normal current density, which is directly proportional to the corrosion rate. Different real structures consisting of pipelines and/or well casings are simulated to investigate the factors affecting four types of CP interferences, namely, anodic, cathodic, combined and induced, with special emphasis on the cathodic one. The results reveal that the application of impressed current CP systems creates DC SCC on other nearby unprotected structures. This is an inherent potential problem with the application of such systems which dominates with decreasing soil conductivity, and/or increasing the anode current density and its proximity to the protected structures. On the contrary, SCC can be reduced by using multi-groundbed anodes. In addition, it is found that the cathodic interference is more serious than anodic one, and the combined and induced interferences can also cause severe corrosion. Finally, it can be concluded that the BEASY software is a very helpful tool for future planning before installing any structure, where it gives the possible CP interferences on any nearby unprotected metallic structures.     

埋地长输管道交流腐蚀现场状态及其风险评估

超高压输电线路对埋地管道的交流干扰问题日益突出,国内对其交流腐蚀缺乏风险评估.以裸露X65钢模拟埋地长输管道防腐蚀涂层缺陷,采用交、直流电流及电位的在线监测和腐蚀失重等方法,研究了高压输电线路交流干扰特征及其对管道阴极保护系统的影响规律.结果表明,当土壤介质条件基本不变时,电位与电流的变化存在相似性;适当调节阴极保护电...     

Determination of parameters of corrosion protection of underground pipelines from noncontact measurements of current

Possibilities of the method of noncontact measurements of current for the on-line assessments of the state of corrosion protection of different sections of a system of underground pipelines, the detection of places of improper insulation, and, in complex with contact electrometry, for the determination of the distribution of the current density of cathodic polarization and components of the transient resistance are shown.     

On the cathodic protection of thermally insulated pipelines

Thermal insulation and corrosion protection of heated pipelines used in moving oil/gas and heated products are accomplished industry-wide by using protective and insulating coatings supplemented by cathodic protection to protect any defected coating areas. A series of tests are carried out to study how the resistivity of the applied insulating layer polyurethane (PUR) can be affected by its specific gravity (as function of its porosity), as well as, the salt (NaCl) concentration in the surrounding electrolyte (water). The current densities required for cathodic protection of insulated steel pipe at the worst condition (i.e., lower resistivity of the insulating material) at ambient and elevated temperatures were determined. The results have showed: that a lower PUR foam density has lower percentage closed cells which lead to a decrease in the PUR foam resistivity. An increase in the salt concentration up to about 3.5% NaCl leads to about 40% increase in the current intensity required for CP of the insulated steel sheets. In this investigation zinc wire of diameter 5 mm was used as a sacrificial anode in two different manners parallel and spiral. The sacrificial anode was fixed adjacent directly to the electrical insulation under the PUR foam shows a complete protection of the pipes, i.e., about – 920 mV vs. Cu/CuSO₄, in the salty water with about 3.5% NaCl; this method guarantees optimum protection. The experiments performed at different temperatures up to 60 °C showed that increasing the temperature has a slight positive effect.     

Passivation treatment for inhibition of hydrogen absorption in chromium-plated steel

Hydrogen permeation transients for passivated chromium-plated steels were measured at room temperature as a function of cathodic charging current density. The passivated film on chromium plating is shown to be an effective barrier to hydrogen at low cathodic charging current density (40 and 100 A cm^–2). The passivated film can be reduced to chromium at higher cathodic charging current density (1 and 10 mA cm^–2), promoting hydrogen absorption significantly.     

Electromagnetic method and procedures of nondestructive inspection of the corrosion protection of underground pipelines

A triune mathematical model of an electromagnetic field is proposed, and procedures of fast noncontact inspection of underground pipelines are proposed. Methods and devices are developed for the determination of the distribution of cathodic protection current and the transition resistances of protective coatings in different sections of underground pipelines. The technology of integral, differential, and local inspections of main pipelines is described.     

A method of noncontact measurements of currents for control over corrosion protection of underground pipelines

We consider the basic principles and potentials of noncontact measurements of currents for control over corrosion protection of underground steel pipelines. The characteristics of the magnetic field and a solution of the inverse problem for a rectilinear current are analyzed. The necessary and sufficient conditions for the determination of current on measurements of the magnetic field above the route are formulated. We describe algorithms, an example of using a BIT-3 noncontact current meter, and full-scale tests for the insulation control and cathodic protection of a main gas pipeline. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 35, No. 3, pp. 105–112, May–June, 1999.     

An empirical model for parameters affecting energy consumption in boron removal from boron-containing wastewaters by electrocoagulation

In this study, it was investigated parameters affecting energy consumption in boron removal from boron containing wastewaters prepared synthetically, via electrocoagulation method. The solution pH, initial boron concentration, dose of supporting electrolyte, current density and temperature of solution were selected as experimental parameters affecting energy consumption. The obtained experimental results showed that boron removal efficiency reached up to 99% under optimum conditions, in which solution pH was 8.0, current density 6.0 mA/cm(2), initial boron concentration 100mg/L and solution temperature 293 K. The current density was an important parameter affecting energy consumption too. High current density applied to electrocoagulation cell increased energy consumption. Increasing solution temperature caused to decrease energy consumption that high temperature decreased potential applied under constant current density. That increasing initial boron concentration and dose of supporting electrolyte caused to increase specific conductivity of solution decreased energy consumption. As a result, it was seen that energy consumption for boron removal via electrocoagulation method could be minimized at optimum conditions. An empirical model was predicted by statistically. Experimentally obtained values were fitted with values predicted from empirical model being as following; [formula in text]. Unfortunately, the conditions obtained for optimum boron removal were not the conditions obtained for minimum energy consumption. It was determined that support electrolyte must be used for increase boron removal and decrease electrical energy consumption.