By: MANAN JAIN (130010114016) T32 RENISH PIPALIYA (130010114046) T38 Faculty name: Patel Dipsa Institute name: Food procrssing Technology department A.D.patel institute of technology Karamsad CORROSION CORROSION
Dec 27, 2015
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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