Effect and Mechanism of Cathodic Protection Conditions on the Corrosion Behavior of X80 Steel Under HVDC Interference

Recently, the problem of high-voltage direct current (HVDC) interference suffered by buried oil and gas pipelines has attracted widespread attention among research communities. Hence, accurately assessing the corrosive impact of HVDC interference on buried metal pipelines and performing effective protection procedures for the prevention of such corrosion have become priority issues that need to be resolved for producing reinforced pipelines. To date, the effect of the cathodic protection of the pipeline on the corrosion behavior of X80 steel under HVDC interference has rarely been reported. Hence, in this study, the corrosion behavior of X80 steel without cathodic protection conditions before HVDC interference and the effect of these protection conditions on the corrosion behavior of X80 steel under HVDC interference were studied through laboratory simulation experiments. Results showed that the corrosion rate of X80 steel was 170.81 mu m/h without cathodic protection under 20 V DC interference for 1 h. When the cathodic protection pretreatment potentials were-0.85,-0.95,-1.05, and-1.20 V, the corrosion rates were 124.39, 87.13, 54.56, and 1.45 mu m/h, respectively. The effect of various cathodic protection pretreatment potentials on the corrosion behavior of X80 steel under HVDC interference was clarified based on the product surface membrane layer, polarization, and EIS results. For the cathodic protection pretreatment potential of-0.85 to-1.05 V, the sample products after HVDC interference mainly showed a mixture of green rust GR1, calcium, and magnesium deposits; the corrosion rate of the sample products decreased with the increasing negative cathodic protection pretreatment potential under DC interference due to the gradual increase in the quality of the calcium and magnesium deposited layer on the surface of the sample products. At-1.20 V cathodic protection polarization potential, the corrosion rate of the sample products was substantially lower than that at other potentials because passivation of the products occurred under the combined action of high cathodic protection potential and HVDC interference.