Under Deposit Corrosion Behavior of Pipeline Steel in Oxygenated Medium

Using a self-designed array multi-electrode system, the under deposit corrosion behavior of X65 pipeline steel in oxygenated seawater environment under the condition of sea sand coverage was studied, and the non-uniform corrosion process of pipeline steel was analyzed. The results showed that the working electrode in the sea sand coverage area was the anode, and the cations generated by the dissolution of anode diffused to the bare area, which would reduce the pH of working electrode surface in this area, thereby causing corrosion. With the continuous formation of the porous corrosion product layer, the working electrode near the sea sand coverage area gradually became the main anode area, and serious non-uniform corrosion occurred in this area. CaCO₃ precipitation formed on the surface of the working electrode farther from sea sand coverage area. The precipitation layer had a certain protective effect on the substrate, and kept the working electrode in this area as a cathode all the time, so that the working electrode was not corroded.