Corrosion Failure Causes of Transportation Pipeline for Produced Water of Lime Coagulation and Clarification Treatment

A Q235B carbon steel pipeline for conveying produced water of lime coagulation and clarification treatment in a power plant in Shanxi Province corroded and leaked in a short period of time after operation. In this paper the corrosion failure causes of the pipeline were analyzed through physical and chemical inspection of the failed pipeline and field coupon tests, combined with Lagelier empirical index. The results indicated that the corrosion reaction of carbon steel in water led to the increase of pH in microcathode area, inducing the rapid nucleation and deposition of CaCO₃ on the surface of carbon steel under the water condition of low alkalinity and high hardness. However, uniform protective film did not form under such conditions. Instead, oxygen concentration difference cells formed due to the heterogeneity of sediments on carbon steel surface, which was the main cause of the corrosion failure of the carbon steel pipeline.