Galvanic corrosion behavior of deposit-covered and uncovered carbon steel

Highlights: • Corrosion of steel under sulfur-containing deposit is more severe than bare steel. • Corrosion under deposit is accelerated at 60 °C by coupled with uncovered region. • Wire beam electrode was used to reveal the localized corrosion under deposit. - Abstract: The galvanic effect between the mixed deposit-covered electrode and bare electrode in CO₂-containing formation water was studied by electrochemical measurements and surface characterization. It is found that the bare electrode always acts as anode while the deposit-covered electrode always acts as cathode at 25 °C. The polarity reverses at the late stage at 60 °C due to the formation of FeCO₃ on the bare electrode. Wire beam electrode was used to determine the initiation and propagation of localized corrosion under deposit. Current and potential maps of WBE reveal that severe localized corrosion occurs at the deposit-covered electrodes