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:

SO4^2- + 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.