Purpose

The corrosion of buried steel pipelines is becoming more serious because of stress corrosion, stray current corrosion and other reasons. This paper aims to study the various alternating current (AC) interference densities on the stress corrosion cracking behaviors of X80 steel samples under cathodic protection (CP) in the simulated soil electrolyte environment by using an electrochemical method.

Design/methodology/approach

The change of corrosion rate and surface morphology of the X80 steel samples at various AC current densities from 0 to 150 A/m² or CP potential between −750 and −1,200 mV in the soil-simulating environment was revealed by the electrochemical methods and slow strain rate testing methods.

Findings

The results revealed that with the increase of interference density, the corrosion potential of the X80 steel samples shifted to the negative side, and the corrosion pitting was observed on the surface of the sample, this may cause a danger of energy leak. Moreover, the corrosion rate was found to follow a corresponding change with the stress–strain curve. Besides, with the introduction of the CP system, the corrosion rate of the X80 steel working electrode decreased at a low cathodic potential, while showed an opposite behavior at high cathodic potential. In this study, the correlation between AC stray current, cathodic potential and stress was established, which is beneficial to the protection of oil and gas pipeline.

Originality/value

Investigation results are of benefit to provide a new CP strategy under the interference of AC stray current corrosion and stress corrosion to reduce the corrosion rate of buried pipelines and improve the safety of pipeline transportation.

中文翻译：

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交流杂散电流干扰下API X80钢的应力腐蚀及阴极保护研究

目的

由于应力腐蚀、杂散电流腐蚀等原因，埋地钢管的腐蚀日益严重。本文旨在通过电化学方法在模拟土壤电解质环境中研究各种交流电（AC）干扰密度对阴极保护（CP）下X80钢样品应力腐蚀开裂行为的影响。

设计/方法/方法

通过电化学方法揭示了在模拟土壤环境中，在0 到 150 A/m ^{2 的}各种交流电流密度或 -750 到 -1,200 mV 的 CP 电位下，X80 钢样品的腐蚀速率和表面形貌的变化。应变率测试方法。

发现

结果表明，随着干扰密度的增加，X80钢试样的腐蚀电位向负侧移动，试样表面出现腐蚀点蚀，存在能量泄漏的危险。此外，发现腐蚀速率随应力-应变曲线发生相应的变化。此外，随着CP体系的引入，X80钢工作电极在低阴极电位下的腐蚀速率降低，而在高阴极电位下则表现出相反的行为。本研究建立了交流杂散电流、阴极电位与应力之间的相关性，有利于油气管道的保护。

原创性/价值

研究结果有利于在交流杂散电流腐蚀和应力腐蚀的干扰下提供一种新的CP策略，以降低埋地管道的腐蚀速率，提高管道运输的安全性。