Effects of Desulfotomaculum sp on corrosion behaviour of mild steel and aluminium in sea water

The microbiologically influenced corrosion of mild steel and aluminum in sea water (SW) caused by a sulfate reducing bacterium (SRB), Desulfotomaculum sp was investigated. The corrosion rates were evaluated at intervals of ten days for a period of sixty days using gravimetric and electrochemical methods. Results showed that corrosion rate decreased with exposure time after initial increase. The plot of the electrode potential (EP) with the exposure time shows a decrease as resistance increased due to the corrosion product formed on the surface of the metals. Aluminum recorded a maximal EP reduction (-0.85 mV) after 60 days of incubation, with an onset potential of -0.53 mV after 10 days. The more negative the EP, the greater the tendency to form ions and hence to corrode. The average corrosion rate of mild steel and aluminum coupons in the presence of SRB was 4-fold higher compared to coupons on media without Desulfotomaculum sp.