Corrosion behavior of carbon steel in presence of sulfate-reducing bacteria in seawater environment
Résumé
The influence of sulfate-reducing bacteria (SRB)on the corrosion behavior of carbon steel was studiedin a laboratory test-loop, continuously fed with nutrient supplemented North Sea seawater. The mainparts of the test-loop, represented by two separated flow cells, were fitted with steel specimens. The test-loop was operating anoxically for 2200 h and each flow cell was three times inoculated with Desulfovibrioalaskensis or Desulfovibrio desulfuricans species. Additionally, each flow cell was two times perturbed with antimicrobial treatments. Steel specimens exposed in flow cells exhibited comparable appearance andsystems responding similarly to inoculations and antimicrobial treatments. The effect of the inoculations in both flow cells on the steel coupons electrochemical behavior was materialized as lower resistanceto corrosion and higher surface activity or occurrence of localized pitting events. The localized surfaceattacks recognized in both flow cells after inoculations continued to progress with the time, althoughbacterial activity was temporarily suppressed by antimicrobial treatment. Post-exposure sample evalu-ations might suggest that, some particular steel surface areas have been subjected to a dramatic change in the corrosion mechanism from initial localized attack to general corrosion. The long-term exposureof the carbon steel specimens resulted in identifiable formation of biofilms and corrosion products. Cor-rosion deposits were characterized by a specific structure built of iron sulfides (FeS), sulfated green rust(GR(SO42−)), magnetite (Fe3O4), Fe(III) oxyhydroxides (FeOOH), chukanovite (Fe2(OH)2CO3), carbonatedgreen rust (GR(CO32−)) and some calcareous deposits. Presented factual evidence reinforced the idea thatsulfidogenic species in natural seawater environment may cause localized damage with a specific surfacepattern; however, this does not necessarily lead towards significantly elevated corrosion rates.
Domaines
Génie des procédés
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