Mechanical Properties and Performance of Composite-Reinforced Steel Pipelines in Wet Environments with Cathodic Protection

Composites have seen increased usage for repair of pipelines. The performance of the entire metal-composite system has not been extensively addressed with regard to corrosion of the substrate and adhesion loss when the conditions are wet and the substrate is cathodically protected. In this work we have investigated the influence of corrosive environments on the performance of composite repair systems for pipelines. Earlier in this work we used FEA models to evaluate a composite patch for pipelines and the present research includes the experimental results for both patch and full-wrap composite repairs in simulated and field environments. The effect of impacts, cathodic protection, long term immersion, and soil corrosivity have been investigated by monitoring variables related to potential and conductivity of the electrolyte. We have also tested mechanical properties via four point bend on specimens intentionally exposed to ASTM cathodic disbondment tests. We have also evaluated the performance of these repairs in a modified ASTM G8 cathodic disbondment test with the addition of high pressure cyclic loading. By monitoring these variables, loss of adhesion and integrity in the composite-metal system is addressed.