摘要
[目的]埋地油气管道一般采用防腐层与阴极保护联合防护,在长期运行过程中,防腐层存在老化与剥离现象。防腐层剥离区缝隙内存在较高IR降,保护电流分布不均匀,阴极保护电流难以达到缝隙深处,易造成剥离区缝隙内管道欠保护。脉冲电流阴极保护相比传统阴极保护具有较大优势,对于高阻介质环境中的管道具有更好的阴保效果。目前对脉冲阴极保护机理缺乏全面的认识,脉冲阴极保护应用于防腐层剥离系统的适用性尚需验证。[方法]采用缝隙模拟实验装置,研究脉冲阴极保护下剥离防腐层(涂层)管道极化行为,探究保护电位、脉冲频率、阴保占空比及缝隙间隙等参数对保护效果的影响。[结果]由于剥离涂层的屏蔽效应,脉冲阴极保护产生的极化电位梯度主要集中于剥离区缝口附近,缝隙深处电位随剥离深度增加而正移,逐步接近自然腐蚀电位。[结论]相比常规阴极保护,脉冲阴极保护有利于改善剥离区局部电位与电流分布,增大剥离区内有效保护距离。随阴极保护电位负移,缝隙内局部电位下降,剥离区下有效保护深度增加;脉冲频率与占空比较高时,脉冲阴极极化持续时间较长,阴极电流中双电层充放电电流减小,有效保护电流增加,利于提高剥离区内阴极极化水平和有效保护距离。脉冲电流阴极保护所需电流较小,电位分布更均匀,有效保护距离更长。(图8,表1,参20)
[Objective]Buried oil and gas pipelines are typically safeguarded by both anti-corrosive coating and cathodic protection.However,over time,the anti-corrosive coating degrades and may peel off during extended operation.High IR drop in the crevice results in uneven distribution of protection current,making it challenging for the cathodic protection current to penetrate the depth of the crevice.This often results in inadequate protection of the pipeline in the crevice within the peeling zone.Pulsed current cathodic protection(PCCP)offers superior advantages over traditional methods and provides enhanced protection for pipelines in high-resistance medium environments.At present,the comprehensive understanding on the mechanism of PCCP is inadequate,prompting the need for further research to validate its applicability in systems with peeled anti-corrosive coating.[Methods]A study was conducted using a crevice simulation experimental device to analyze the polarization behavior of pipelines with peeled anti-corrosive coatings under PCCP,along with the influence of parameters such as the protective potential,pulse frequency,cathodic protection duty cycle,and crevice clearance on the protection effect.[Results]The polarization potential gradient generated by PCCP was mainly concentrated near the seam of the peeling zone due to its shielding effect.As the depth of peeling increased,the potential within the crevice shifted positively,eventually nearing the free corrosion potential.[Conclusion]Compared with conventional cathodic protection,PCCP can improve the local potential and current distribution in the peeling zone,thus extending the effective protection range in the zone.The effective protection depth beneath the peeled coating increases with the negative shift of the cathodic protection potential Ecp and the drop of the local potential in the crevice.Higher pulse frequency and duty cycle prolong the duration of pulsed cathode polarization,leading to decreased charging and discharging current of the electrical double la
作者
吴长访
钟婷
冯永强
石胜明
闫茂成
刘文会
高博文
WU Changfang;ZHONG Ting;FENG Yongqiang;SHI Shengming;YAN Maocheng;LIU Wenhui;GAO Bowen(PipeChina Institute of Science and Technology;PipeChina North Pipeline Co.Ltd.;Institute of Metal Research,Chinese Academy of Sciences)
出处
《油气储运》
CAS
北大核心
2024年第6期649-655,共7页
Oil & Gas Storage and Transportation
关键词
油气管道
阴极保护
缝隙腐蚀
脉冲电流
剥离涂层
oil and gas pipeline
cathodic protection
crevice corrosion
pulse current
peeled coating
