摘要
【目的】埋地钢质管道高绝缘性3PE防腐层剥离将会造成“阴极保护屏蔽”,其引起的局部环境下管道金属腐蚀已成为油气管道安全运行的主要威胁之一。对防腐层剥离区内管道金属腐蚀发展规律进行全面评估,研究不同土壤环境中剥离防腐层下管道电位分布特征与腐蚀行为,有利于制定有效的管道腐蚀防护策略。【方法】以X80钢为例,采用自制的防腐层剥离厚度可调实验装置,通过对剥离区不同位置进行金属阴极保护电位测试,并结合扫描电子显微镜、激光共聚焦显微镜的结果,研究了滨海盐渍土、内地盐碱土、红黏土及草甸土4种土壤溶液环境中,沿防腐层剥离延伸方向的管道金属阴极保护电位分布情况及剥离区不同位置局部微区腐蚀特征。【结果】管道金属的阴极保护电位会随剥离区深度发展而正移,有效的阴极保护主要集中在防腐层破损开口附近;随着剥离区深度的延伸,阴极保护电位会快速衰减,直至剥离区深处管道接近自然腐蚀状态,即达到阴极保护屏蔽区;剥离区阴极保护电位分布与有效保护范围主要受剥离区液膜厚度、土壤水的含盐量(即土壤电阻率)影响,高盐含量(电阻率低)的滨海盐渍土更有利于阴极保护电流穿透,且剥离区空间对离子扩散与迁移过程具有限制作用,进而显著影响电流的分布及有效保护范围。【结论】对比管道在不同土壤中的腐蚀行为,阴极保护的有效保护范围从大到小依次为滨海盐渍土、红黏土、内地盐碱土、草甸土。埋地管道在滨海盐渍土、红黏土中局部腐蚀严重,而在内地盐碱土、草甸土中主要表现为均匀腐蚀;同时,剥离区管道腐蚀速率明显高于开放的防腐层破损点处。(图10,表2,参28)
[Objective]The disbondment of high-insulation 3PE anti-corrosion coatings on buried steel pipelines leads to“cathodic protection shielding”,a phenomenon that results in metal corrosion of pipelines in local environments,posing a challenge to the safe operation of oil and gas pipelines.A comprehensive evaluation of corrosion development patterns for pipelines within disbondment zones,along with an investigation into the potential distribution characteristics and corrosion behavior of pipelines covered by disbonded anti-corrosion coatings in various soil environments,is conducive to formulating effective strategies for pipeline corrosion protection.[Methods]A self-made experimental device with adjustable disbondment thickness for anti-corrosion coatings based on X80 steel was used to perform cathodic protection potential tests on metal at various positions within disbondment zones.Utilizing scanning results from scanning electron microscopes and laser scanning confocal microscopes,the cathodic protection potential distribution along the pipeline metal in the direction of disbondment extension,as well as the localized micro-area corrosion characteristics at different positions within the disbondment zones,were examined across four soil solution environments:coastal saline soil,inland saline-alkali soil,red clay,and meadow soil.[Results]The cathodic protection potential of the pipeline metal was observed to shift to be more positive with increasing depth within the disbondment zones.Effective cathodic protection was primarily concentrated near the damage opening of the anti-corrosion coatings.The cathodic protection potential declined rapidly as the depth of the disbondment zones increased,eventually reaching deeper positions where the pipeline approached a natural corrosion state and cathodic protection shielding occurred.The cathodic protection potential distribution and the effective protection range within the disbondment zones were influenced by the thickness of the liquid film present and the salt content(soil resistivity)of the soil water.Coastal saline soil,characterized by high salt content and low resistivity,was found to facilitate greater penetration of the cathodic protection current.Additionally,the space of the disbondment zones exerted a limiting effect on the ion diffusion and migration processes,significantly impacting the distribution of current and the effective protection range.[Conclusion]Comparing the corrosion behavior of pipelines in different soils reveals a descending order of effective cathodic protection range as follows:coastal saline soil,red clay,inland saline-alkali soil,and meadow soil.Buried pipelines are particularly vulnerable to severe localized corrosion in coastal saline soil and red clay,whereas they predominantly experience uniform corrosion in inland saline-alkali soil and meadow soil.Moreover,the corrosion rate of pipelines within disbondment zones is significantly higher than that observed at exposed positions where the anticorrosive coatings are damaged.(10 Figures,2 Tables,28 References)
作者
陈振华
陈洪源
张腾
闫茂成
高博文
CHEN Zhenhua;CHEN Hongyuan;ZHANG Teng;YAN Maocheng;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》
北大核心
2025年第12期1386-1394,共9页
Oil & Gas Storage and Transportation
基金
国家管网集团定向委托项目“管道及LNG接收站腐蚀分级评价与管控体系研究”,AQWH202205。
关键词
埋地管道
防腐层
剥离
阴极保护屏蔽
土壤腐蚀
电位分布
buried pipeline
anti-corrosion coating
disbondment
cathodic protection shielding
soil corrosion
potential distribution
