oest 740 022008 - university of hawaiimcooney/oest740/biocorrosion_ppt.pdf · oest 740 022008....
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BiocorrosionBiocorrosion
OEST 740022008
OutlineOutline
Introduce corrosionIntroduce corrosion
Atmospheric corrosion
Bi iBiocorrosionOxygen gradients
SRB
Role of EPS
Biocoenosis
Summaryy
Corrosion
ElectrochemicalElectrochemical Anodic – oxidation
cathodic reductioncathodic - reductionResult – electric circuit
CorrosionCorrosion
pH dependent
Atmospheric Corrosion
> 60% humidity> 60% humidityRelatively slow
CorrosionOxidative layer or polarizing film
D t i ll tibilit f t l tDetermines overall susceptibility of metal to corrosion
Depolarizing agents
Polarizing film
BiocorrosionBiocorrosion
Microbiological influenced corrosion (MIC)Microbiological influenced corrosion (MIC)Electron-transfer Hypothesis – biocorrosion is a process in which metabolic activities ofis a process in which metabolic activities of microorganisms associated with metallic materials supply insoluble products whichmaterials supply insoluble products which are able to accept electrons from the base metalmetal
Organic component of matrixE i iEnzymes present in matrix
MIC
Oxygen gradients anoxic niches
SRBSulfate reducing bacteria (SRB)
AnaerobicAnaerobic Sulfate – electron acceptorDesulfovibrio desulfuricansDesulfovibrio desulfuricans
Binding properties of matrixBinding properties of matrix
Bacteria change EPS composition accordingBacteria change EPS composition according to substrate/substratumProteins lipids polysaccharides nucleicProteins, lipids, polysaccharides, nucleic acids, etc
BiocoenosisBiocoenosis
Interaction of all organisms in a particular habitat
Why care?Why care?
MIC is believed to contribute 30-78% ofMIC is believed to contribute 30-78% of corrosionUS $100 billion/yr to prevent or retartUS $100 billion/yr to prevent or retart corrosion Di US ili i f $700Direct costs to US military aircrafts > $700 million/yrDOD corrosion problems - $10 billion/yr
SummaryyBiocorrosion occurs in both aquatic and
i l h bi d i di iterrestrial habitats under various conditionsResults from presence and physiological activities
f i bi l i lli fof microbial consortia on metallic surfaceBiofilms promote interfacial physiochemical reactions not favored under abiotic conditionsEffect of EPS matrix and impact of enzymes in p ybiofilms needs to be addressed furtherContribute significantly to the billion dollarContribute significantly to the billion dollar problem on corrosion