Early identification of stress corrosion cracking of P110 low alloy steel in downhole fluid by electrochemical noise measurement

Electrochemical noise (EN) measurements were applied to detect the stress corrosion cracking (SCC) of API P110 low alloy steel in simulating CO2-containing downhole fluid during the slow strain rate test (SSRT). Several statistical parameters of potential and current transients were defined, and they were proven to be indicative of the metastable and stable pitting, as well as the initiation and propagation processes of microcracks. The EN results showed that the amplitude and lifespan of current transients increase with the CO2 concentration. The increasing SCC susceptibility of P110 steel is mainly attributed to the decreasing pH at the crack tip, which not only accelerated the rupture of passive film on crack walls but also prolonged the lifespan of cracks advance. EN measurement may be a promising technique for the early diagnosis of SCC.