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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!