Corrosion Behavior of 20 Pipeline Steel in Soil of Tahe Region in Xinjiang

Twelve locations along a pipeline in Tahe region of Xinjiang were selected to bury coupons. The physicochemical properties of the soil at the buried sites were tested, and their corrosion ratings were given. The relationship between soil corrosion and cathodic protection was comprehensively analyzed. The results show that the corrosion rate of pipeline was not directly proportional to the corrosion rating of soil, due to the complexity of soil corrosion. Based on GB/T 21448-2017 standard, four locations on the pipeline met the criteria of cathodic protection potential less than -850 mV and potential polarization degree greater than 100 mV, seven sites on the pipeline met the criterion of potential polarization degree greater than 100 mV only. When the protection potential of pipeline met the protection criteria of GB/T 21448-2017 standard, the corrosion rates of the pipeline were lower than 0.025 4 mm/ a (specified in NACE RP0775-2005 standard), and the protection degrees for the pipeline were higher than 85% (specified in GB/T 21447-2018).