Research On The Corrosion Mechanism Of Sulfate-reducing Bacteria Under Cathodic Protection

The metal corrosion caused by Sulfate reducing bacteria?SRB?,and other microorganisms bring serious damage to the national economy.Severe attention has been paid to the corrosion mechanism of SRB.With the widespread use of cathodic polarization as the effective corrosion protection method,it is more and more importane to explore the corrosion mechanism of SRB under polarization.In this paper,the electroactive characteristics of SRB biofilm under polarization was studied using electrochemical method,and put an insight into the electron transfer pathway between SRB and polarized electrodes.The interaction between SRB and alloys the infuece of SRB on corrosion behaviour of Al-Zn-In-Cd aluminum alloys were also studied and the corresponding corrosion mechanism were proposed.The interaction between SRB and polarized electrode and the influence of SRB on the corrosion bahavior of high-strenght steel EQ70 were first studied in this paper.Metabolic factors detection and electrochemical measurements showed that the cathodic polarization of-0.85 VSCE enhanced SRB metabolic activity,and accelerated the corrosion rate of EQ70.While the cathodic polarization of-1.05 VSCE inhibited the metabolic activity of SRB and EQ70 was well protected under this potential.Corrosion product analysises showed that the application of cathodic protection led to the transformation of sulfide rusts into carbonates rusts.While exploring the interaction between SRB and polarized electrode,we found that the metabolic activity of SRB was accelerated at-0.85 VSCE polarized potential.Thus,we investiged the interaction between SRB and 5052 aluminum alloys whose potential was around-0.85 VSCE in sea water.The results showed that SRB metabolic activity was promoted in the presense of 5052 aluminum alloys,and 5052 aluminum alloys corrosion rate was accelerated by SRB in return.However,the promotion effect was much smaller comparing with that of the polarization potential of-0.85 VSCE and iron,which may be related with the compact protective oxide film formed on alloy surface.The influence of SRB on the corrosion bahavior of Al-Zn-In-Cd aluminum alloys showed that SRB promoted the corrosion of Al-Zn-In-Cd aluminum alloys mainly by accelerateing the cathodic reaction,the presence of SRB led to the transformation of corrosion product of Al-Zn-In-Cd aluminum alloys from Al₂O₃ into NaAlO₂.