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CORROSION OF STEELCORROSION OF STEEL

STRACTUR IN SEA BEDSTRACTUR IN SEA BEDSEDIMENTSEDIMENT

GUIDE BY:

MR.SANJAY KU. SAHOONAME:GAUTAM BEHERA

B TECH 7 th sem

REGD NO:0701105083ROLL NO:26602


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CONTENTS

INTRODUCTION SBS CORROSION FACTOR

SBS CORROSION MECHANISM MEASUREMENT OF METALCORROSION RATE IN SBS

SBS CORROSION EVALUATIONAND PREDICTION CONCLUSIONS

REFERENCE


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INTRODUCTIONv Sea bed sediment (SBS) corrosion is animportant topic in marine environment

corrosion science. In terms of corrosionlocality, marine environment can be dividedinto atmospheric zone, splash zone, tidal

zone, immersed zone, and seabed sedimentzone. Generally it is considered that theseabed sediment zone has leastcorrosiveness. Development in marine oilexploitation and engineering including marine

cables, steel rigs, pipelines and other marinefacilities is increasing demanding integratedinvestigation and research on corrosion.Therefore, scientific solution and referenceto corrosion in marine oil exploitation andsea bed pipelines can be provided.


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SBS COROSION FACTOR

SBS defination: SBS is a special soilbeneath sea water. It is soaked tosome extent. In this two-phasedsystem, there is no sole gas phase.

Physical and chemical character:

Different from land soil,salina soil& tideland soil.

Factors on which SBS corrosion

depends


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ELECTRO CHEMICAL CORROSION FACTOR

Temperature

Particle size

Electrical resistance Salinity

Dissolved oxygen

PH value


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q INFLUENCE OF TEMPERATURE Affect the kinetics process of

electrode reaction Direct relationship

q INFLUENCE OF PARTICLE SIZE SBS division on basis of particle size Relationship between particle size and

corrosion rate


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FIGURE 1 SHOWS THREE YEAR CORROSI RATE OF DIFFERENT STEELS N MUD AN

SAND


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FIGURE 2 SHOWS THE CORROSION RATE WITH DIFFERENT GRAIN SIZE

OF MILD STEEL


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q INFLUENCE OF ELECTRICAL

REISTANCE Reflection of SBS electricalconductivity

Resistance increases with burialdepth

Relationship between electricalresistance and SBS particle size

q INFLUENCE OF SALINITY General salinity including SBS Relationship between salinity and

corrosion rate Effect of CL ions


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q INFLUENCE OF pH VALUE

Sea water a complicated system pH of surface layer SBS Effect of Alkalophilic bacterium on pH

value of SBS Favourable for propagation of

anaerobic bacteria


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MIC FACTOR

Include SRB

Redox potential (Eh)

Sulfur potential (Es) Ratio of Fe to Fe

Organism content


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q SRB CONTENT MIC is mainly SRB corrosion Wider distribution in sea SRB content in Liaodong Bay SBS

is 0 ~ 460 unit per g wet mud SRB content in south china sea

SBS is 0 ~ 9.3

Effect of SRB on corrosion rate


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GRAPH 3 SHOWS CORROSION RATE OF DIFFERENT STEEL IN SEA MUD WITH

BACTERIA


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q , , /Eh Es Fe Feand organismcontent

All affect SRB corrosion Favorable anaerobic condition for SRB

growth

Effect of SRB growth in marineenvironment

Other factors of corrosion


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SBS CORROSION MECHANISM

Electrochemical corrosionmechanism

MIC mechanism

q ELECTROCHEMICAL CORROSIONMECHANISM

Galvanic corrosion Localized corrosion


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Galvanic Corrosion In PipeLine

Localized Corrosion InsideSteel Pipe Line


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Crevice Corrosion In PipeLine

Pitting Corrosion In Pipes


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q MIC MECHANISM

SRB Localized corrosion

Corrosion product Role of SRB King and Miller study

Corrosion rate of SRB is notless than 0.1mm/a

Other function of SRB


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MIC CORROSION PICTURES

MIC Corrosion In SteelPipe Sample

MIC Corrosion In SteelPipe Sample


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Corrosion Pictures

Sea Bed Sediment Corrosion In Marine Pipe


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MEASUREMENT OF METAL CORROSION RATE IN SBS

In situ measurementmethod

Laboratory method


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SBS CORROSION EVALUATION AND PREDICTION Based on weight loss

method

Models to evaluate andpredict corrosion


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CONCLUSION

Research on SBS corrosionis still in developing stage

Some problem need further study

Development in marineindustry demanding moreresearch on SBS corrosion


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REFERENCE

Batt c et al 2002 corros. Eng .sci .&technology.uk 37

Boussiba s 1989 plant cell physiol 30

Dinhhang t et al 2004 nature 427 Fischer k p 1981 mater .perf 20

Jack j r et al 1998 corrosion 54


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