Electrochemical Study on the Macro-Cell Corrosion of Pipeline Steel Partially Covered by Different Kinds of Mineral Deposits

High Resolution Image Download MS PowerPoint Slide This study presents the impact of mineral deposits (SiO 2, Al 2 O 3, and CaCO 3 ) on the corrosion behavior of X65 pipeline steel in CO 2 -containing brine solution with low pH. The study investigates the initiation and propagation of under deposit corrosion (UDC) using a wire beam electrode (WBE) partially covered by different mineral deposit layers, in conjunction with electrochemical measurements and surface characterization. The results indicate that the corrosion behavior varies, depending on the characteristics of the deposit. During the test period, the Al 2 O 3 -covered steel acted as the main anode with more negative potential, while the bare steel acted as the cathode. The SiO 2 -covered steel acted as the cathode with more positive potential and a localized FeCO 3 layer formed beneath the silica mineral. The CaCO 3 -covered steel initially acted as an anode with a more negative potential but transformed into the cathode at the end of the test. Additionally, shallow and small pits were observed beneath the deposits with the depth in the sequence Al 2 O 3 > SiO 2 > CaCO 3 .