Research on Corrosion Behavior of 20 Steel under High Moisture Content and High Cl-Soil Environment in Coalbed Methane Field Production Platform
In order to study the corrosion mechanism of the buried pipeline in soil suffering from produced water flooding in the coalbed methane drainage and production platform,corrosion coupons of 20 steel were installed in-site of buried pipeline in the long term,and the corrosion profile and corrosion production were analyzed by means of SEM,EDS and XRD,and then the corrosion behavior of 20 steel was studied by combining with its long-term soil electrochemical impedance spectroscopy and polarization curve test in soil samples with 20%water content in the laboratory.The results showed that 20 steel exhibited general corrosion with pitting corrosion characteristicsafter being buried for 75 days;long term electro-chemical research further revealed that 20 steel undergoes oxygen polarization corrosion due to during the initial burial stage,and the corrosion process is controlled by oxygen diffusion.As a large amount of Cl-ions penetrated through the loose corrosion product film and formed the pitting nuclei,the corrosion process was controlled by the activation and the diffusion.Therefore,produced water flooding made 20 steel developing into the pitting corrosion from the general corrosion in the influence of the oxygen polarization and Cl-autocatalytic acidification effect,thereby evolving into the perforation and leakage of the pipeline.
20 steelburied pipelinesoil corrosionpitting corrosioncorrosion production film
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