Numerical Study: Mechano-electrochemical effect of X100 buried pipelines with preexisting corrosion defects

Abstract

The new high-strength low alloy steel API X100 is a cost-effective steel grade and has the ability to withstand high operating conditions without the need for increasing pipe wall thickness. However, buried transmission pipelines suffer from external corrosion and cracking, the corrosion kinetics in near-neutral pH environments is not yet fully studied. Therefore, conducting research to contribute to a clearer understanding of the corrosion kinetics in near neutral pH soil environment will therefore have unique novelty when conducted on the modern HSLA steel grades such as API X100. Also, formulating and developing models to simulate the X100 steel pipeline corrosion in nn-pH soil environments is of great importance and benefit to the electrochemical science and assessing the pipeline integrity. This thesis presents and discusses the results of two numerical models conducted on X100 steel, contributing to a clearer understanding of the corrosion kinetics and crack propagation of corroded pipelines occurring in these environments. The results of this research can be used for assessing the integrity of buried oil and gas transmission pipelines, however they can also be extended for the use of other infrastructural and engineering applications such as steel reinforcements of buried structures. Two numerical models were conducted for the purpose of studying the corrosion kinetics and growth rate of a buried pipeline with a semi-elliptical corrosion defect and the crack propagation due to the stress concentration buildup on the defect center. The first model was formulated using Comsol Multiphysics v5.6 and the results showed that the electrolyte potential at the corrosion defect center is shown to be the highest when compared to the remaining geometry. Also, the anodic current density at the corrosion defect center was found to increases from its initial value of 12

Date of Award	Jul 2021
Original language	American English