Corrosion inhibition of deposit-covered X80 pipeline steel in seawater containing Pseudomonas stutzeri

Under-deposit corrosion, a typical corrosion type, is a major threat to the safe running of pipeline steel in marine environment. Under-deposit corrosion behaviour and mechanism still require further investigation, especially when there is participation of microorganisms. In this work, the inhibition of corrosion of deposit-covered X80 pipeline steel due to the presence of Pseudomonas stutzeri in seawater containing CO2 was investigated using weight loss, electrochemical measurements, a wire beam electrode and surface analysis. The results show that steel corrosion rates decline rapidly due to the covered deposit in the presence or absence P. stutzeri, but corrosion rates were slower in the presence of P. stutzeri. The highest corrosion rates were (0.365 +/- 0.021) mm/y and (0.230 +/- 0.001) mm/y in abiotic and biotic conditions, respectively. The corrosion inhibition efficiency of P. stutzeri was reduced in the presence of deposits, because the deposits led to a lowered biological activity. The galvanic current density between deposit-covered and bare specimens in seawater was weakened by P. stutzeri, leading to diminshed corrosion, especially pitting corrosion.