Atlas of continuous cooling transformation (CCT) diagrams applicable to low carbon low alloy weld Metals PDF

Electrochemical measurements (polarisation curves and a.c. impedance) have been conducted on carbon steel coupons exposed to SRB-active environments. Results from a.c. impedance measurements show that very large interfacial capacities are found in such systems, and consequently high capacitive currents are to be expected when conducting d.c. polarisation scans. Further, it is indicated that the interfacial capacitance correlates with the concentration of dissolved sulfide, which in turn, to some degree, correlates with hydrogenase activity. It is suggested that the large and increasing interfacial capacitance is reponsible for the large potential hysteresis generally found in d.c. polarisation curves obtained in these environments. By comparing polarisation curves obtained using different scan rates in an inorganic control environment, it is suggested that an ever increasing interfacial capacitance may be responsible for a misleading conclusion that increased corrosion rates are caused by cathodic depolarisation in SRBactive environments.

Edited by: D. Thierry