<p>The steel pipeline in the oil and gas industry is subject to complex stress-strain due to soil movement along the pipes and internal pressure. As an example, high strength steel pipeline in the Arctic and sub-arctic regions due to harsh geographic environments experience complex stress/strain conditions. In addition to the internal operating pressure, the induced longitudinal strains due to soil movement along the pipe and the induced elasto-plastic local strain distribution is shown to impact the corrosion of the steel pipeline. Local strain distribution on and around defects in the pipeline is of utmost importance especially considering corrosion response of steel pipeline in the proximity of the defects. In this work, we study the effect of defect geometry and density along the pipe on the local stress-strain distribution and subsequent local corrosion activity. We use the finite element method to study the mechano-electrochemical effects of corrosion in high-strength steel, X100 steel, used in pipelines under the effect of soil strain at corrosion defects in a near-neutral pH bicarbonate solution. The modeling is done by coupling solid mechanics at the steel pipe wall and electrochemical activity at the interface between the pipe wall and the surrounding soil. Small strain von Mises yielding criteria is used and corrosion potential, anodic current density, and cathodic current density are characterized and used for this study by looking at the center to edge ratio. The effects of defect depth to pipeline length ratio, defect length to pipeline length ratio, and the defect density along the pipeline on the corrosion activity at the defects are studied. Validation of the model is done against a previous work and the effects of defect geometry and density on corrosion activity are studied. We used a new normalization parameter comparing to the previous work to better characterize the corrosion activity at the defect. In addition, this work studies the effect of uniformly distributed defect density. This work provides an insight based on FE simulation for prediction of localized corrosion on pipelines under complex stress and strain conditions to support recommendations to industry for risk assessment and integrity management. The results show that increased defect depth to pipeline thickness ratio leads&nbsp;to an increase in local stress concentration and subsequently higher corrosion activity. It is also shown that increased defect length to pipe length ratio leads to more distribution of local stress-strain and lower corrosion activity at the defects. Increased number of defects also reduces local stress concentration and subsequent corrosion activity at each defect.</p>

Study of Defect Morphology and Density on Mechano-Electrochemical Effect of Pipeline Corrosion

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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