Electrochemistry and pitting corrosion of nano-scale metallurgical features in pipeline steels

本研究的目的是研究低强度和高强度管道钢（即X65和X100钢）的电化学和各种冶金特征的点蚀，并在纳米和原子长度尺度上将点蚀现象与钢铁冶金相关联。***高强度钢管道的发展使石油/天然气输送取得了显著的经济效益。高强度钢，如X100钢，与低等级钢，如X65钢相比，具有独特的金相组织，可以实现强度、韧性和可焊性的良好结合。这通常包括精细的亚微米结构，通常在几十和几百纳米尺度上。***点腐蚀已被确定为管道泄漏发展的主要机制之一。点蚀的发生在很大程度上取决于钢的冶金特性。高强度钢独特的冶金特性将影响管道的点蚀。迄今为止，对钢铁冶金对管道点蚀影响的研究仍然停留在宏观和统计上。关于钢中腐蚀坑的产生和发展的机理信息还没有完全了解。***在本研究中，电化学原子力显微镜将结合其他表面和电化学技术，同时测量局部电化学腐蚀反应，并在受控环境下以纳米尺度的空间分辨率表征管道钢的冶金特征的三维结构/形貌。具体来说，本研究将促进我们对X65和X100钢的纳米冶金特征的理解，测量这些钢中纳米级成分的电化学行为；并对点蚀的发生和发展进行监测，建立点蚀与钢铁冶金的关系。管道是全国范围内重要的石油/天然气运输网络。确保管道的安全运行对加拿大经济具有重要意义的行业的长期健康至关重要。研究结果将对提高钢材和管道的完整性做出重大贡献，这将是减轻公众对管道安全、环境影响和可靠性担忧的重要基石。此外，该研究将有助于冶金纳米电化学作为管道腐蚀研究的概念和方法的发展。这一开创性的研究结合了电化学、冶金和先进的表面分析技术，预计将为了解管道腐蚀机制建立新的方法和强有力的科学基础

The objective of the proposed research is to study electrochemistry and pitting corrosion of various metallurgical features in low- and high-strength pipeline steels, i.e., X65 and X100 steels, and correlate pitting corrosion phenomenon with the steel metallurgy at the nano-meter and atomic length scales.***    Development of high-strength steel pipelines has enabled significant economic benefits in oil/gas transmission. High-strength steels, such as X100 steel, feature a unique metallurgical microstructure, compared with low grade steels, such as X65 steel, to achieve a good combination of strength, toughness and weldability. This typically includes fine, sub-micron structures, which are usually at tens and hundreds of nano-meter scale.***    Pitting corrosion has been identified as one of the dominant mechanisms for the development of pipeline leaks. Initiation of pitting corrosion depends strongly on the metallurgical features of the steel. The unique metallurgical feature of high-strength steels is expected to affect pitting corrosion of pipelines. To date, research into the effect of steel metallurgy on pipeline pitting corrosion has remained macroscopic and statistical. The mechanistic information as to the exact initiation and growth of corrosion pits in steels has not yet been realized.***    In this research, an electrochemical atomic force microscope, combined with other surface and electrochemical techniques, will be used to simultaneously measure local electrochemical corrosion reactions, and characterize three-dimensional structure/ morphology of metallurgical features in pipeline steels with nano-scale spatial resolution in controlled environments. Specifically, this research will advance our understanding of the nano-scale metallurgical features in X65 and X100 steels, measure electrochemical behavior of the nano-scale constituents in these steels; and monitor pit initiation and growth to establish the correlation of pitting corrosion with steel metallurgy.***    Pipelines are a critical nation-wide network for oil/gas transportation. Ensuring safe pipeline operation is critical for the long-term health of an industry that has great significance to the Canadian economy. The research findings would contribute significantly to improving steels and pipeline integrity, which will be an important cornerstone in alleviating public concerns of safety, environmental impact, and reliability of pipelines. Moreover, the research will contribute to development of metallurgical nano-electrochemistry as a concept and approach for pipeline corrosion research. It is also anticipated that this pioneering research, which integrates electrochemistry, metallurgy and advanced surface analysis techniques, will establish a new methodology and strong scientific baseline for the understanding of mechanisms of pipeline corrosion.**