The modification of oxygen reduction rate induced by bacterial settlement on stainless steel (SS) surfaces immersed in natural seawater was studied as a function of temperature (25 C ≤ temperature ≤ 40 C), imposed potential, and duration of cathodic polarization. Data derived from galvanic couples, potentiostatic polarizations, impedance measurements, and biochemical analyses [adenosin triphosphate (ATP), electron transport system (ETS) activity, and chlorophyll a (Chl a)] were used for this purpose.
The results show that bacterial settlement has a depolarizing effect on oxygen reduction at seawater temperatures <40 C. At these temperatures, the oxygen reduction rate on specimens covered by bacterial slime reaches its steady value 4 to 5 days after cathodic potential is applied. These results can explain how the corrosion rate of SSs in natural seawater decreases when the temperature increases over 40 C. Finally, a model is suggested to correlate the oxygen reduction rate with the bacterial settlement and the duration of cathodic polarization.
