密间隔电位测量(CIPS)中通断周期对埋地管道阴极保护系统的影响

研究了密间隔电位测量(CIPS)过程中恒电位仪电压/电流输出及埋地管道管/地电位随电流中断器通断周期的变化;系统阐述了在使用恒电位仪的阴极保护系统下断电周期的合理设置及通电周期对管/地间通/断电电位的影响。     

基于数值模拟的两种断电电位测量方法对比

测量埋地长输管线断电电位时,参与同步通断的阴极保护站数量的不同将直接影响到断电电位测量结果。运用边界元数值模拟软件BEASYCP对测量断电电位常用的瞬间断电法开展研究,针对同步通断相邻4个和2个阴极保护站的两种测量方法分别进行模拟计算,对比讨论模拟结果,得出应至少同步通断相邻4个阴极保护站的结论并由此给出关于测量方法方面的建议。     

3PE防腐蚀层联合阴极保护对管道的保护效果

采用阴极保护联合3PE防腐蚀层的方法对埋地钢质管道进行了防护。试验模拟了管道3PE防腐蚀层底漆存在、金属基体暴露、金属暴露孔处未与土壤介质接触及与土壤介质完全接触的不同情况,探讨了阴极电流与通电电位之间的关系,研究了通/断电位的负移对试样3PE防腐蚀蚀层阴极剥离的影响。结果表明,试样阴极保护电流的变化与管道3PE防腐蚀层的缺陷存在、土壤接触方式、通电电位密切相关。通/断电电位正于-0.85V(CSE)时,难以阻止试样发生腐蚀,通/断电位过度负移将造成3PE防腐蚀层的阴极剥离,使3PE防腐蚀层提前失效。     

管道阴极保护电位检查片测试方法及应用

根据相关标准规定,钢制埋地管道阴极保护效果评价应采用断电电位指标,现场测试通常使用同步中断法,但其并不适用于无法同步中断管中阴极保护电流、以及受杂散电流干扰的管段。阴极保护电位检查片可以解决这一难题,通过模拟管道防腐层漏点,利用检查片的瞬间断开电位实现近似管道断电电位的测量。本文详细介绍了管道阴极保护电位检查片的适用范围、设计、安装、测试及分析等内容,通过具体实施案例明确了数据记录的规范性,并验证了测试方法的可行性,为该方法的推广应用奠定实践基础。     

极化电位对埋地钢质管道涂层剥离的影响

为了研究提高埋地钢质管道阴极保护电位对管道涂层剥离的影响,对退役的埋地管道提高保护电位,收集管道的通电电位和断电电位数据,并测量涂层的阴极剥离距离。结果表明:当断电电位达到-1.2 V时,管道的通、断电电位绝对值并不一定随着距离的增加而减小;此外,不同防腐涂层管道的阴极剥离距离不同。     

原油长输管道阴极保护有效性评价分析

目的探究原油长输管道阴极保护失效的原因。方法通过管道通/断电电位测试、集输末站内外电位测试和绝缘法兰测试等方法,判断集输管线是否处于有效的保护状态,站内外阴极保护是否存在直流干扰情况,以及绝缘法兰的工作情况。结果 1~#集气站-1~#阀室管道通电电位为-850~1200 mV,断电电位为-773~788 mV,不满足比-850 mV更负的准则。站外管线通/断电电位虽然随着站内阴保电流的增大而增大,但是在电流为6、18 A时,其断电电位分别为-880 mV和-1198 mV,在保护电位范围之内(-850~1200 mV),没有产生过保护,符合国标的要求。站内外阴极保护干扰是客观存在的,可以通过调节及平衡站内外的输出,使站内外管道的保护电位在规定的电位区间之内(-850~1200 mV)。集输末站处的绝缘法兰性能良好,但是锌接地电池基本耗尽。结论管道断电电位没有达到要求,且集输末站内外阴极保护存在相互干扰,是该长输管道阴极保护失效的主要原因。     

一种新型数控高频开关恒电位仪的研制与应用

动态直流杂散电流干扰会导致管道电位持续波动,传统恒电位仪以“恒电位”模式运行时无法根据管道保护电位进行实时调整,阴极保护效果不理想。介绍了一种以断电电位为控制电位运行的新型数控高频开关恒电位仪,并在某管道进行了现场测试。测试结果表明：配合土壤管测量断电电位,新型恒电位仪在动态直流杂散电流干扰下控制电位准确、调整实时、运行平稳,显著提升了线路的阴极保护效果。     

忠武管道阴极保护断电电位测量结果分析

采用GPS卫星同步断电法对忠武管道进行了断电电位测量,对结果进行了分析,评价了忠武管道阴极保护系统的有效性,并提出了改进建议.结果表明,三层PE管道相比于环氧粉末涂层管道更容易出现过保护现象,而且还容易受到干扰;电位是反应管道所处状态的主要指标,阴极保护系统的通电电位呈规律分布,但断电电位影响因素复杂,无明显规律.     

国内外管道阴极保护电位测量方法差异分析

阴极保护是保障油气管道安全运行的可靠技术。国际上普遍应用断电电位评价管道阴极保护状态。介绍了国内管道断电电位测量技术现状,存在的问题是断电电位测量延迟时间存在差异,不能获得准确的管-地极化电位。以新发布的美国腐蚀工程师协会标准NACE TM0497-2012为例,阐述了国际上普遍公认的阴极保护电位标准测试方法,包括测试断电电位的断电时间、电压冲击峰持续时间、参比电极精度和参比电极放置方法等。最后,提出了借鉴NACE TM0497-2012技术先进性,修订国家标准GB/T 21246-2007的建议。     

钢质管道外腐蚀直接评价(ECDA)过程中密间隔电位(CIPS)检测方法的应用

本文介绍了CIPS密间隔电位测量的基本原理和5种检测模式及其应用情况,并通过一次成功的实施CIPS密间隔电位测量,解析检测数据的得出通/断电电位、横/纵向电位梯度在管道防腐层破损点处的不同数据分布规律,通过该规律可以实现使用CIPS密间隔电位测量的方法,对管道阴极保护电位和管道防腐层破损点的定位。     

用试片断电法测量埋地管道的断电电位和去极化过程

采用试片断电法测量管道的断电电位来评价埋地管道的阴极保护效果。在室内建立了一个埋地管道外加电流阴极保护系统,用试片断电法测量了管道缺陷处的断电电位和去极化过程,并对测量结果进行分析。结果表明,断电电位应在断电后50～100ms之间读取,按此测量试片去极化过程中形成的电位差值,该值与100mV的比较结果可以判断阴极保护效果。     

塔河油田管道阴极保护电位测试与分析

采用断电法、极化探头法和试片断电法对塔河油田不同管道的阴极保护电位进行测量,发现了日常管理中测试方法的误差,提出针对不同阴极保护情况的管道应采用不同的测试方法来消除IR降和干扰电流的影响。     

Elektrochemische Untersuchungen zum kathodischen Korrosionsschutz mit Unterbrecherpotentiostaten

Electrochemical investigations into cathodic corrosion protection using an interruption-potentiostat Stationary and instationary electrochemical investigations were carried out on iron in the cathodic and on platinum coated titanium in the anodic region for further developments on the field of the potentiostatic cathodic corrosion protection. Using the results obtained an interruption-potentiostat was developed, which allows to avoid the normally used reference-electrode at the potentiostatic cathodic protection. This becomes possible by using this interruption-potentiostat and an inert anode, whereby the flowing current is interrupted periodically for a short time. In the cut off time the anode, which is normally used as counter electrode, is now after a delay of about 30 μs the reference electrode to measure the existing potential E_ist of the iron which has to be protected. This potential will be compared to the potential E_soll adjusted at the potentiostat and the difference E_ist – E_soll is used for the regulation of the protection current flowing during the switch on time. The investigations carried out for some time with such an interruption-potentiostat show that iron can be protected cathodically in this way without the undesired generation of hydrogen.     

典型压气站区域阴保系统阳极地床故障检测与分析

本文介绍了对西部地区某处典型压气站站内区域阴保系统故障的检测与分析过程,检测手段包括恒电位仪运行状况检查,阴保电位、阳极地床接地电阻测试和不同阳极连接方式下阴保系统联调。经过现场检测联调和分析,证实了区域阴保系统保护效果欠佳是由阳极地床故障引起的,确定了各路阳极地床的保护范围,并对治理方案提出了建议。     

乍得原油管道阴极保护系统异常原因分析及解决方法

介绍了乍得原油管道工程阴极保护系统的设计、调试与试运,分析了阴极保护系统调试中遇到的自腐蚀电位异常以及阀室阴极保护电流泄漏问题。通过完全摘除临时阴极保护所用牺牲阳极以及在恒电位仪输出和输出端增加绝缘解决了上述问题。     

Critical questions and answers about cathodic protection

ABSTRACT

Cathodic protection has been in use for almost two hundred years, yet there still exist a number of misunderstandings surrounding its application. In this paper, we question some common statements and beliefs to determine whether they are based on fact or fiction. Our questions include: What is the origin of the ubiquitous ?0.85?V_CSE cathodic protection criterion and why does it work? Does cathodic protection really stop corrosion or simply reduce it to negligible levels? What does the instant off potential tell us and is it really the true polarised potential? Does hydrogen gas cause cathodic disbonding? Do the potential shifts measured during interference testing indicate real interference? The answers to these questions are important because they allow the correct interpretation of field and experimental data, based on a true understanding of the electrochemical and thermodynamic basis of cathodic protection.     

断电法在管道阴极保护效果评价中的运用

通过测试管道保护电位,并依据电位准则对管道的保护效果进行评价,是最简便而通行的方法。但是在通电状态得到的电位并不是管道实际的保护电位。而采用卫星同步断电装置,利用断电法能有效消除测试中IR降的影响,不过这种方法也存在一定程度的局限性。为了解决这些问题,对这些方法进行了一定程度的修正并形成了一套更准确更符合工程现场实际的新方法。同时,介绍了断电电位的测试及修正,并讨论了牺牲阳极系统、不均匀极化等因素对测试结果的影响。     

Langzeiterfahrungen mit einem kathodischen Korrosionsschutzsystem für Stahl in Beton

Long‐term experiences with a cathodic protection system for steel in concrete In 1986 in Germany the first cathodic protection system for reinforced concrete structures was put into service. Installation, commissioning and the regular monitoring were scientifically supported. Due to necessary traffic related reconstruction measures the system was switch off after 15 years of service. Investigations carried out during that period should verify laboratory test results at a real structure and furthermore yield information on the long‐term behaviour concerning durability, temperature dependence, potential distribution, chloride migration etc. With increasing time of service the protection criteria could only be met by increasing the transformer rectifier voltage (the system worked in the constant voltage mode). Extensive investigations of the anode material (conductive polymer wire with a copper core) after 15 years of service showed that irreversible changes substantially decreased the polymer's conductivity limiting the functionality. Today, these kind of anodes are not used any more for the application in cathodic protection systems of reinforced concrete structures.     

Influence of cathodic protection on the lifetime extension of painted steel structures

For corrosion to occur on a coated metal surface, an electrochemical double layer must be established. Hence, the adhesion between the substrate and the coating must be weakened to enable a separate thin layer of water to be formed at the interface from water that has permeated the coating. To prevent the failure of a painted coating, we applied a cathodic protection method. This method has been controversial for a few years because cathodic protection can induce cathodic delamination of the entire surface, especially near the anode, and also because it is not effective on a not-wetted surface from the anode. We therefore evaluated the efficiency of cathodic protection for 700 days in an atmospheric environment and performed surface observation, AC impedance measurements and corrosion tests. In the case of a noncathodic protected painted steel specimen, blisters formed after 100 days and grew in number for the remainder of the test. However, cathodic protection of the painted steel increased the coating resistance and extended the lifetime of the coating. According to our calculation with the BEASY program, the thickness of the water film under a rain condition barely influenced the protection potential. The high voltage of the cathodic protection and the subsequent cathodic delamination caused the paint to peel off near the anode. Hence, the protection voltage should be controlled in accordance with changes to the environmental condition.     

The effects of hydrogen embrittlement by cathodic protection on the CTOD of buried natural gas pipeline

For the corrosion protection of natural gas transmission pipelines, two methods are used, cathodic protection and a coating technique. In the case of cathodic protection, defects are embrittled by hydrogen occurring at crack tips or surfaces of materials. It is, however, very important to evaluate whether cracks in the embrittled area can grow or not, especially in weld metal. In this work, on the basis of elastic plastic fracture mechanics, we performed CTOD testing under various test conditions, such as potential and current density. The CTOD of the base steel and weld metal showed a strong dependence on the test conditions. The CTOD decreased with increasing cathodic potential and current density. The morphology of the fracture surface showed quasi-cleavage. Cathodic overprotection results in hydrogen embrittlement at the crack tip.