CORROSION DETECTION ON NATURAL GAS PIPELINES WITH MICROLINEAR POLARIZATION RESISTANCE SENSORS

摘要

This paper presents an experiment adapting linear polarization resistance based corrosion sensors, originally developed for aerospace applications, to measure the corrosion rate of API 5L ERW grade-B steel natural gas line pipe using micro-sized linear polarization resistance (μLPR) sensors made from the same alloy and grade steel. Sensors were installed under a 15 mil coating of fusion-bonded epoxy, at various proximities to a 1/8 inch defect introduced at a weld joint and along the pipe seam. After sensor installation the pipe was buried in an controlled environment with soil amended to a pH of five. This environment was held at a temperature above 35°C while soil moisture content was modulated between wet and dry cycles, each lasting seven days. LPR and environmental measurements were sampled at five minute intervals. Post processing was performed to convert the LPR measurements to a surface-loss. Comparisons made in the data showed API 5L ERW grade-B steel natural gas pipelines were highly susceptible to corrosion along the seam, with all sensors showing activity in this region early in the experiment. Sensors adjacent to a weld joint began to display evidence of corrosion more slowly. These results verify the ability of μLPR sensors to measure corrosion activity under protective coatings in underground environments.