Simple project for high School

1. STUDY OF THE
EFFECT OF
METAL COUPLING ON
THE
RUSTING OF IRON
PRESENTED BY
NAME: SANJAY PS
CLASS: XII-A
YEAR: 2015-2016

2. Certification :
It has been certified that Sanjay PS
Studying in XII-A(Science), during
the academic year 2015-16 has
completed a project on the study of
effect of metal coupling on the
rusting of iron and has given a
satisfactory account of this in their
project report
SURYA GOPALAKRISHNAN(PGT
Chemistry)
Signature

3. Declaration :
I Sanjay PS and of Class XII A
(Science), Kendriya Vidyalaya No 1
Palakkad, declare that the following
project on the study of the effect of
metal coupling on the rusting of iron
has been accomplished under the
able guidance of our Chemistry
Teacher, Smt.Surya Gopalakrishnan
Kendriya Vidyalaya No1 Palakkad
Date:

4. Acknowledgement:
I would like to express our sincere
gratitude to Smt.Surya
Gopalakrishnan, our chemistry
teacher, whose help and
encouragement made this project
possible. We would also like to thank
Mr. Ravi, the lab Assistant for his
help during the completion of this
project.
XII A (Science)
Kendriya Vidyalaya Palakkad

5. INDEX:
 Introduction
 Mechanism of corrosion of
meta
 Electrochemical
Mechanism(rusting)
 Methods of Prevention of
Corrosion
 Economic Effect
 Aim of this project
 Requirements
 Procedure
 Observation
 Conclusion
 Bibliography

6. INTRODUCTION
Metal corrosion is the most common
form of corrosion. The corrosion occurs
at the surface of the metal in forms of
chemical or electrochemical reactions.
This process significantly reduces the
strength, plasticity, toughness and other
mechanical properties of the metallic
material. However, because of the metal
and its alloys is still the most important
pipe and structure materials, the cost of
corrosion grows significantly with the
growth of industries. Thus many
scientists focus on the research of
corrosion control in order to reduce the
cost of replacing the rusting metal
material. Nowadays, there are mainly

7. two corrosion control methods that are
very popular in the world. One is
impressed current and another is
sacrificial anode cathode protection
system. In this project, we will focus on
the mechanism and application of the
sacrificial anode cathode protection
system.
Mechanism of corrosion of metal
General Principle of Corrosion:Reaction
is the fundamental reaction during the
corrosion process, which the electron
can flow from certain areas on the metal
surface to other areas through a
solution which can conduct electric
currents.

8. Basically, both anodic and cathode
reactions have to balance each other
out, resulting in a neutral reaction. Both
anodic and cathodic reactions occur
simultaneously at the same rates.
What’s more, the site of these
electrodes may consist of either two
different kinds of metals, or they may

9. be on different areas of the same piece
of metal, resulting a potential difference
between the two electrodes, so that the
oxidation reaction of the metal at the
anode and formation of negative ions at
the cathode can take place at the same
time.
Similar electrical potentials may also be
developed between two areas of a
component made of a single metal as

10. result of small differences in
composition or structure or of
differences in the conditions to which
the metal surface is exposed. That part
of a metal which becomes the corroding
area is called the “anode” ; that which
acts as the other electrode of the
battery is called “cathode” which does
not corrode, but is an important part of
the system. In the corrosion systems
commonly involved, with water
containing some salts in solution as the
electrolyte. Corrosion may even take
place with pure water, provided that
oxygen is present. In such cases
oxygen combines with the hydrogen
generated at the cathode, removing it
and permitting the reaction to go on.

11. Rusting: an Electrochemical Mechanism
Rusting may be explained by an
electrochemical mechanism. In the
presence of moist air containing
dissolved oxygen or carbon dioxide, the
commercial iron behave as if composed
of small electrical cells. At anode of
cell, iron passes into solution as ferrous
ions. The electron moves towards the
cathode and form hydroxyl ions. Under
the influence of dissolved oxygen the
ferrous ions and hydroxyl ions interact

12. to form, i.e., hydrated ferric oxide.
Methods of Prevention of Corrosion and
Rusting
Some of the methods used:-
1) Barrier Protection: In this method, a
barrier film is introduced between

13. iron surface and atmospheric air.
The film is obtained by painting,
varnishing etc.
2) Galvanization: The metallic iron is
covered by a layer of more reactive
metal such as zinc. The active metal

14. losses electrons in preference of iron.
Thus, protecting from rusting and
corrosion.

15. AIM OF THIS PROJECT
In this project the aim is to
investigate effect of the metals
coupling on the rusting of iron. Metal
coupling affects the rusting of iron. If
the nail is coupled with a more
electro-positive metal like zinc,
magnesium or aluminium rusting is
prevented but if on the other hand, it
is coupled with less electro –positive
metals like copper, the rusting is
facilitated.

16. REQUIREMENTS
1) Two Petri dishes
2) Four test-tube
3) Four iron nails
4) Beaker
5) Sand paper
6) Wire gauge
7) Gelatin
8) Copper, Zinc and Magnesium
strips
9) Potassium ferricyanide solutions
10) Phenolphthalein

17. PROCEDURE
1) At first we have to clean the
surface of iron nails with the
help of sand paper.
2) After that we have to wind zinc
strip around one nail, a clean
copper wire around the second
and clean magnesium strip
around the third nail. Then to
put all these three and a fourth
nail in Petri dishes so that they
are not in contact with each
other.

18. 3) Then to fill the Petri dishes with
hot agar agar solution in such a
way that only lower half of the
nails are covered with the
liquids
4) Keep the covered Petri dishes
for one day or so.

19. 5) The liquids set to a gel on
cooling. Two types of patches
are observed around the rusted
nail, one is blue and the other
pink. Blue patch is due to the
formation of potassium ferro-
ferricyanide where pink patch is
due to the formation of
hydroxyl ions which turns
colorless phenolphthalein to
pink.

20. OBSERVATION
S.No Metal Pair Colour
of the
patch
Nails
rusts or
not
1 Iron-Zinc
2 Iron-
Magnesium
3 Iron-
Copper

21. CONCLUSION
It is clear from the observation that
coupling of iron with more
electropositive metals such as zinc
and magnesium resists corrosion and
rusting of iron. Coupling of iron with
less electropositive metals such as
copper increases rusting.

22. BIBLIOGRAPHY
For our project we have taken help
from following sources;
1) Comprehensive (practical
Chemistry-XII)
2) Internet- www.wikipedia.com
3) NCERT Chemistry Textbooks
4) http://projects.icbse.com/chemis
try