By: MANAN JAIN (130010114016) T32RENISH PIPALIYA (130010114046) T38

Faculty name: Patel DipsaInstitute name: Food procrssing

Technology departmentA.D.patel institute of technology

Karamsad

CORROSIONCORROSION

What is Corrosion?

Corrosion is the oxidation of a metal due to an ELECTROCHEMICAL reaction. The oxidizing agent is most often O2 (atmospheric corrosion) or H+ (chemical corrosion) or both.

Requirements for corrosion

Active metal

Water

Oxygen (atmospheric corrosion)

Acid (chemical corrosion)

High temperature

Example of Atmospheric Corrosion

Corrosion on wing of Navy aircraftF/A-18C Hornet

Example of Stress CorrosionAloha Flight 243 (28 APR 1988)

Stress Corrosion Crackingtensile stress and

corrosive environmentscracks are initiated at

corrosion areastensile stresses propagate

the crackcorrosion further

deteriorate crack

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Forms of

corrosion

• Stress corrosionStress & corrosionwork togetherat crack tips.

• GalvanicDissimilar metals arephysically joined. Themore anodic onecorrodes. Zn & Mgvery anodic.

• Waterline corrosionMaximum amount of corrosion takes place beneath the surface of the water meniscus

• PittingDownward propagationof small pits & holes.

FORMS OF CORROSION

• Ranks the reactivity of metals/alloys in seawaterm

ore

anodic

(a

ctiv

e)

more

cath

odic

(i

nert

)

PlatinumGoldGraphiteTitaniumSilver316 Stainless SteelNickel (passive)CopperNickel (active)TinLead316 Stainless SteelIron/SteelAluminum AlloysCadmiumZincMagnesium

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GALVANIC SERIES

Factors influencing corrosion

Nature of metalPurity of metalTemperatureHumidity of airPresence of impurities in airInfluence of pH

How do we suppress corrosion?

Applications of Cathodic Protection

Galvanized SteelZinc coating

Sacrificial AnodesShip Hulls

Subs (free flooding areas)

Los Angeles Class Sub

Arleigh-Burke Destroyer

Galvanizing

Galvanizing is the process of coating iron or steel sheets with a thin coat of zinc to prevent them from rusting.

It is most widely used for protection of iron from atmospheric corrosion in the form of roofing sheets , wires , pipe , nail , bolts , screw , bucket etc,

TinningTinning is coating tin over the iron or steel

articles.It possesses considerable resistance against

atmospheric corrosion.Moreover because of non-toxic nature of tin ,

tinning is widely used for coating steel , copper and brass sheets , used for manufacturing containers for storing foodstuffs , ghee , oil etc.

Tinned-copper sheets are employed for making cooking utensils and refrigeration equipment.

Corrosion Prevention

CoatingsBarrier filmsInhibitive

PigmentsSacrificial

treatmentsPaint

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