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Matakuliah : S0372 – Kimia Teknik Sipil
Tahun
: Ganjil 2007/2008
KINDS OF METAL CORROSION
PERTEMUAN 10
KINDS OF METAL CORROSION
• Corrosion in water
• Atmosphere Corrosion
• Corrosion in Limited place.
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CORROSION IN WATER
1. Corrosion by Freshwater.
a. Korosi by clean water.
At metal which not glorify will be formed by the
following reaction:
L + 2H2O  L(OH)2 + H2
b. Corrosion by clean water and O2
Hence reaction of above will mount to higher level
valence because earning oxidation on the.
2L + 3H2O + 3/2 O2  2L(OH)3
This reaction take place at water near by surface because
O2 diffusion can into water.. To water which in hence O2 will
very minimum more than anything else its silent water, so
that only formed L(OH)2. For Example Fe(OH)2
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2. Corrotion by Sea Water
a. Factor influencing incidence of corrosion by water go out to
sea to metal:
- Dampness of air
- Oxygen
- sea water pH
- Speed of sea current
- Existence of difference of metal humanity potency or
structure which is not homogeneous
- Existence of other sea animal or microbe
- Temperature
- Dissolve element rate in sea water
- Imperfect metal connected
- Less precise painting.
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b. Place – attacked sea water corrosion.
All metal able to have an effect on direct like : which
is sink or hit sprayer also when hitting influence of
sea atmosfir.
c. Effect of sea water corrosion.
 Go down strength him of materials and goods till
can endanger. Flimsy Ship wall and in a moment
will leak.
 Nature of seeing ugly.
 Can generate damage related to.
 Required by defrayal of big conservancy.
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d. Control of water corrosion go out to sea which
during the time often conducted:
1. With painting of and the like.
Paint anti korosi, used by paint marine which
generally have the nature of holding up to :
reaction of chemistry, weather, dampness,
dirts and easy to doing it. Part and parcel of
painting is sweeping of surface to all kinds of
rust pickings dirt, scale mill, sea dirts, oil, dirt
and others.
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2. Other ways besides paint
a. Metallic Coating
Arranging in layers with protector of other metal, both for
more august from is metal of base and also less august.
b. By using two nearby metal in galvanic line of him, so that
not happened galvanic corrosion.
c. Labouring equivalent surface possible. Link of two metal
which not stick correctness often represent beginning
dot of corrosion also result of connected, what not
flatten.
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ATMOSPHERE CORROSION
Seen from facet of aggresive corrosion, hence atmosphere
earn us to the:
1. Mountain atmosphere or hinterland.
2. Atmosphere go out to sea and coastal edge (marine)
3. Industrial area and urban
4. Industrial area in coastal periphery.
Mountain atmosphere which there no cauldron of mount have
fire to hence only containing aqueous vapour, O2, and CO2,
which is have cauldron usually contain H2S very corrosive and
poisonous at metal.
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- Atmosfir go out to sea and coastal very aggresive
caused by sprinkling of aeolian sea water into the
air and pregnant sprinkling of NaCl and very
corrosive other salts because will form strong
electrolyte.
- Industrial Area Atmosfir releasing many gas CO2,
SO2, NO2,HCl, Cl2, if there are any water very
corrosive at metal.
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CORROTION IN LIMITED PLACE
Because limited place its certain volume, in fact environment
can be arranged so that is not aggresive, its way for example
passing draining dismayed etcetera. But on the contrary when
not be controlled, room corrosion will generate the problem of
which complicated enough.
If there are any wet shares, hence when heat, water will
condense and when again chilled of dew. The condensation will
become the source of continuous korosi.
For this event, is needed by good ventilation till if (there are)
any which condensing castaway of exit.
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