Action of sulfate reducing bacteria

Shipwrecks and Salvage‎ > ‎6. Corrosion at Depths‎ > 

Describe the action of sulfate reducing bacteria around deep wrecks

  • Seawater contains approximately 840 ppm of sulfates.
  • Much corrosion of metals in deep water is caused by anaerobic bacteria that reduce sulfate to sulfide:

SO42- + 5H2O + 8e → HS + 9OH

  • This reduction half-equation is accompanied by the oxidation half-equation of the metal involved, such as iron:

Fe → Fe2+ + 2e

  • Combining the above two equations:

4Fe + SO42– + 5H2O → 4Fe2+ + HS + 9OH

  • The products react to form the insoluble compounds of iron sulfide and iron hydroxide:

4Fe2+ + HS + 7OH → FeS(s) +3Fe(OH)2(s) + H2O(l)

  • The main sulfate-reducing bacterium is Sporovibrio desulfuricans, which obtains energy from the reduction process.