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

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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.