Corrosion of pipelines under dynamic direct current interference

Abstract While pipeline corrosion under direct current (DC) interference has been investigated, there is few work conducted under dynamic DC existing in reality. This work studied corrosion of an X52 pipeline steel under dynamic DC interference in a diluted sodium bicarbonate solution, which simulated the soil electrolyte. Electrochemical measurements, weight-loss testing and surface characterization were used to determine the effects of DC current density, pulse frequency and wave form of the DC interference on the corrosion. It is found that the dynamic DC can accelerate the steel corrosion at a rate more rapidly than that under the static DC at specific current densities. However, the corrosion enhancement is not significant, especially at low DC current densities. The role of the AC component in the pulse DC in corrosion becomes more apparent as the DC current density increases. When the pulse frequency of the DC increases, the corrosion rate decreases. The wave form of the dynamic DC does not obviously affect the steel corrosion.