23-02-2013, 12:35 PM
Study of effect of metal coupling in rusting of Iron
[attachment=51605]
INTRODUCTION
Metals and alloys undergo rusting and
corrosion.The process by which some
Metals when exposed to atmospheric
conditions i.e.,moist air, carbon dioxide
form undesirable compounds on the
surface is known as Corrosion. The
compounds formed are usually oxides.
Rusting is also a type of corrosion but
the term is restricted to iron or products
made from it. Iron is easily prone to
rusting making its surface rough.
Chemically, rust is a hydrated ferric
oxide Fe2O3.nH2O. Rusting may be
explained by an electrochemical
mechanism. In the presence of moist air
containing dissolved oxygen or carbon
dioxide, the commercial iron behaves as
if composed of small electrical cells.At
iCBSE.com
anode of cell, iron passes in to solution
as ferrous ions.
Fe Fe2+ +2e-
The electrons from the above reaction
move towards the cathode and form
hydroxyl ions
H2O + (O) + 2e- 2OHUnder
the influence of dissolved oxygen
the ferrous ions and hydroxyl ions
interact from rust,i.e., hydrated ferric
oxide.
2Fe2+ +H2O +(O) 2Fe3+ + 2OH-
2Fe3+ + 6OH- Fe2O3.3H2O (rust) or
2Fe(OH)3
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If supply of oxygen is limited the
corrosion product may be black
anhydrous magnetite, Fe3O4 .
Methods OF
PREventing corrosion
Some of the methods used to prevent
corrosion are discussed here :
1.Barrier Protection. In this method, a
barrier film is introduced between iron
surface and atmospheric air.The film is
obtained by painting , varnishing etc.
2.Galvanization. The metallic iron isn
covered by a layer of more active metal
such as zinc.The active metal loses
electrons in preference to iron
Zn Zn2+ + 2e-
Thus, protecting iron from rusting and
corrosion.
iCBSE.com
MATERIALS AND EQUIPMENTS
Two petridishes
Four test-tubes
Four iron nails
Beaker
Sand paper
Wire gauge
Gelatin
Copper, Zinc and Magnesium
strips
Potassium ferricyanide solution
Phenolphthalein
iCBSE.com
EXPERIMENTAL PROCEDURE
1. Clean the surface of iron nails with
the help of sand paper. Wash them
with carbon tetrachloride and dry
on filter paper.
2. Wind a clean zinc strip around one
nail, a clean copper wire around the
second and clean magnesium strip
around the third nail.Put all these
three and the fourth nail in Petri
dishes so that they are not in
contact with each other.
[attachment=51605]
INTRODUCTION
Metals and alloys undergo rusting and
corrosion.The process by which some
Metals when exposed to atmospheric
conditions i.e.,moist air, carbon dioxide
form undesirable compounds on the
surface is known as Corrosion. The
compounds formed are usually oxides.
Rusting is also a type of corrosion but
the term is restricted to iron or products
made from it. Iron is easily prone to
rusting making its surface rough.
Chemically, rust is a hydrated ferric
oxide Fe2O3.nH2O. Rusting may be
explained by an electrochemical
mechanism. In the presence of moist air
containing dissolved oxygen or carbon
dioxide, the commercial iron behaves as
if composed of small electrical cells.At
iCBSE.com
anode of cell, iron passes in to solution
as ferrous ions.
Fe Fe2+ +2e-
The electrons from the above reaction
move towards the cathode and form
hydroxyl ions
H2O + (O) + 2e- 2OHUnder
the influence of dissolved oxygen
the ferrous ions and hydroxyl ions
interact from rust,i.e., hydrated ferric
oxide.
2Fe2+ +H2O +(O) 2Fe3+ + 2OH-
2Fe3+ + 6OH- Fe2O3.3H2O (rust) or
2Fe(OH)3
iCBSE.com
If supply of oxygen is limited the
corrosion product may be black
anhydrous magnetite, Fe3O4 .
Methods OF
PREventing corrosion
Some of the methods used to prevent
corrosion are discussed here :
1.Barrier Protection. In this method, a
barrier film is introduced between iron
surface and atmospheric air.The film is
obtained by painting , varnishing etc.
2.Galvanization. The metallic iron isn
covered by a layer of more active metal
such as zinc.The active metal loses
electrons in preference to iron
Zn Zn2+ + 2e-
Thus, protecting iron from rusting and
corrosion.
iCBSE.com
MATERIALS AND EQUIPMENTS
Two petridishes
Four test-tubes
Four iron nails
Beaker
Sand paper
Wire gauge
Gelatin
Copper, Zinc and Magnesium
strips
Potassium ferricyanide solution
Phenolphthalein
iCBSE.com
EXPERIMENTAL PROCEDURE
1. Clean the surface of iron nails with
the help of sand paper. Wash them
with carbon tetrachloride and dry
on filter paper.
2. Wind a clean zinc strip around one
nail, a clean copper wire around the
second and clean magnesium strip
around the third nail.Put all these
three and the fourth nail in Petri
dishes so that they are not in
contact with each other.