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