Effects of Seawater - Mixed Transportation on Scaling and Corrosion Behavior of the Submarine Pipeline

Abstract

In order to ensure the safety of pipeline flow and clarify the scaling and corrosion risks of seawater - mixed pipeline transportation scheme, the change of water scaling tendency after adding seawater was analyzed based on the actual on - site working conditions of an oil field in South China Sea, and the deposition state of scale layers was simulated to carry out corrosion simulation evaluation experiment. To study the effects of adding seawater on the scaling corrosion of pipeline steel, the average corrosion rate was tested by weight loss method, the scanning electron microscope and energy dispersive spectrometer were employed to observe the corrosion morphology and analyze the corrosion products, and the surface corrosion morphology of the substrate was observed by a laser confocal microscope. Meanwhile, in - situ galvanic corrosion experiments were carried out to investigate the effect of scale deposition on the electrochemical behavior of pipeline steel corrosion. Results showed that the proportion of seawater in the submarine pipeline and the type and content of corrosive ions in the seawater affected the scaling risk of the submarine pipeline transportation system. On the one hand, the formation of the scale layer reduced the overall corrosion tendency of the inner wall of the pipeline; on the other hand, the uneven distribution of the deposited scale layer on the surface of the substrate changed the potential state of the substrate surface, formed a local galvanic battery and thus promoted the emergence and development of local corrosion pits.

Keywords

• pipeline steel|seawater - mixed transportation|scaling tendency|under - deposit corrosion|localized corrosion