Study of internal corrosion of natural gas pipelines in thin electrolyte layers

研究的总体目标是加深对天然气管道内腐蚀的认识，并定量预测管道上的腐蚀增长。 内腐蚀是天然气管道失效的主要原因。1990~2012年艾伯塔省天然气管道失效原因为内腐蚀，占53.2%。天然气管道的内腐蚀是独一无二的。它与管壁内侧形成薄达数十微米的电解层有关。此外，腐蚀同时发生在多个步骤中，通常是协同作用在一起。目前，与现有的关于液体管道腐蚀的文献相比，在薄电解液层中研究这一问题的工作有限。为了定量预测腐蚀增长，以改进管道完整性管理，需要进行大量的工作来获得有关腐蚀基本原理的知识。 拟议的研究将建立在申请者在与项目相关的领域已有的经验和成就的基础上，解决科学和技术方面的差距。在这项研究中，将使用能够精确控制和测量钢材表面电解液层厚度的测试设备。扫描开尔文探头和自制的微电极技术将使在薄电解液层中进行动电位极化和电化学阻抗测量成为可能。参数的影响，包括电解液层厚度，溶液化学和pH，温度，操作压力，二氧化碳/硫化氢分压，甲醇和醋酸浓度，钢的冶金等将被确定。这项研究还将通过生物测试和电化学测量来研究含有硫酸盐还原菌的薄电解液层中的微生物腐蚀和点蚀。为了定量预测天然气管道内部的腐蚀增长速度，将建立力学模型。建立了用于确定腐蚀物种浓度和溶液pH的水化学模型，以及综合多个步骤和影响因素来确定内部腐蚀速率的电化学腐蚀模型。 这项研究具有高度的原创性、创新性，并与一个具有国家重要性的问题格外相关。研究成果将包括新知识和新模型，有助于为天然气管道内腐蚀奠定坚实的科学基础，并使管道运营商能够有效地管理这一问题。这项研究将制定一项高素质的人才培训计划，以满足行业对新一代管道工程师的需求。预计这项研究将进一步巩固加拿大在管道腐蚀研究方面的全球领先声誉。

The overall objective of the research is to advance the understanding of internal corrosion of natural gas pipelines and quantitatively predict the corrosion growth on the pipelines. Internal corrosion is a main contributor to failures of natural gas pipelines. Failure of natural gas pipeline in Alberta from 1990 to 2012 was resulted from internal corrosion at a rate of 53.2%. Internal corrosion of natural gas pipelines is unique. It is associated with the generation of an electrolyte layer as thin as tens of microns on the interior of pipe wall. Moreover, the corrosion occurs in multiple steps simultaneously, often synergistically interacting together. Currently, there has been limited work to investigate the problem in thin electrolyte layers, compared with the existing literature on corrosion for liquid pipelines. Considerable work will be required to gain knowledge on the corrosion fundamentals in order to quantitatively predict the corrosion growth for improved pipeline integrity management. The proposed research will be built upon the applicant's established experiences and accomplishments in the areas relevant to the project, addressing both the scientific and technical gaps. In this research, testing facilities enabling accurate control and measurements of the thickness of an electrolyte layer on the steel surface will be used. A scanning Kelvin probe and home-made micro-electrode techniques will enable potentiodynamic polarization and electrochemical impedance measurements in thin electrolyte layers. Parametric effects, including the electrolyte layer thickness, solution chemistry and pH, temperature, operating pressure, CO2/H2S partial pressure, methanol and acetic acid concentrations, steel metallurgy, etc., will be determined. The research will also investigate microbial corrosion and pitting corrosion in the thin electrolyte layers containing sulfate-reducing bacteria by biotesting and electrochemical measurements. Mechanistic models will be developed to quantitatively predict the corrosion growth rate on interior of natural gas pipelines. A water chemistry model is developed to determine the concentrations of corrosive species and solution pH, and an electrochemical corrosion model will integrate multiple steps and affecting factors to determine the internal corrosion rate. The research is highly original, innovative and exceptionally relevant to an issue of national importance. The research outcomes will include new knowledge and new models, contributing to a strong science base in internal corrosion of natural gas pipelines and enable pipeline operators to effectively manage the problem. The research will develop a highly qualified personnel training program to meet the industry's need for a new generation of pipeline engineers. It is expected that this research will further solidify Canada's global reputation for leadership in pipeline corrosion research.