Download - 37242980 Corrosion Ppt
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CORROSION:TYPES
EFFECTS &
PREVENTION
PRESENTED BY:
Aaradhna Mang la
10 E
Roll No 2
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What is Corrosion
When a metal is attacked by the substance around itsuch as moisture, acids, etc., it is said to corrode andthis process is called corrosion.
We have observed that iron articles are shiny whennew, but get coated with a reddish brown powderwhen left for some time. This process is generally
called rusting of iron.
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Corrosion causes damage to car bodies, bridges, iron railings,ships, and to all objects made of metals, specially those of iron. It is
a serious problem. Every year an enormous amount of money is
spent to replace damaged iron.
Effects of corrosion
iron
Iron reacts with moist air and acquires a
coating called rust. It obtains reddish brown layer.
copper
Copper turns green to form coppercarbonate.
It reacts with moist carbon dioxide in the air.
silver
Silver articles turn black.
It reacts with sulphur in air to form a layer ofsilver sulphide.
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Conditionsfor iron torust
The consequences of corrosion are many and varied
and the effects of these on the safe, reliable andefficient operation of equipment or structures areoften more serious than the simple loss of a mass ofmetal. Failures of various kinds and the need forexpensive replacements may occur even though theamount of metal destroyed is quite small.
Reduced Strength
Downtime of equipment
Escape of fluids
Lost surface properties
Reduced value of goods
Economic losses
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CORROSION PREVENTION:-
Electrically insulate the two metals from each other. Unless they arein electrical contact, there can be no galvanic couple set up.
Coating the two materials or if it is not possible to coat both, thecoating shall be applied to the more noble, the material with higherpotential.
Another way is to keep the metals dry and/or shielded from ioniccompounds (salts, acids, bases), for example by painting orencasing the protected metal in plastic or epoxy, and allowing themto dry.
Proper selection of materials with known resistance to the serviceenvironment .
Control pH, chloride concentration and temperature
Cathodic protection and/or Anodic Protection.
Regular mechanical cleaning if possible.
Chemical treatment with biocides to control the population ofbacteria.
Complete drainage and dry-storage.
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THANK YOU!