Project is from the chapter Electrochemistry . Project is based on the rusting of iron when coupled with different metals . One of the easiest projects in chemistry. Please do like , share and comment if my work helped you ;)

2. CERTIFICATE
This is to certify that the project has been satisfactorily performed by Master
RUSHIL AGGARWAL studying in NAVY CHILDREN SCHOOL of class XII-A under the
guidance of Mr. Anit Rana during the academic year 2015-2016.
Signature of Head Of Department Signature of External Examiner
School Stamp

3. Acknowledgement
I would like to express my sincere gratitude to my
Chemistry mentors Mr. Anit Rana and Mrs. Vishu for
their vital support guidance and encouragement without
which this project would not have come forth from my
side.
I would like to express my heartily gratitude to the lab
assistants Mrs. Sanchita , Mr. Pandurang and Mr. Vivek
for their support during the making of this project .
I would like to thank my parents and friends who have
helped me with their valuable suggestions and guidance
has been helpful in various phases of the completion of
the project.
I would like to acknowledge the Almighty God who made
all the things possible.

4. INTRODUCTION
ELECTROCHEMICAL MECHANISM (Rusting)
METHODS OF PREVENTION OF CORROSION
AIM
MATERIALS REQUIRED
PROCEDURE
OBSERVATION
ASSOCIATED REACTIONS
CONCLUSION
BIBLIOGRAPHY
Index

5. INTRODUCTION
Metals and alloys undergo rusting and
corrosion. The process by which some metals
when exposed to atmospheric condition 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 .
Titanic‘s bow exhibiting microbial corrosion
damage in the form of ‘rusticles’

6. 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 to form rust,
i.e., hydrated ferric oxide.

7. Methods of Prevention of
Corrosion and Rusting
Some of the methods used to prevent corrosion and rusting are –
Barrier Protection –
In the method , a barrier film is introduced between iron surface and
atmospheric air. The film is obtained by painting, varnishing etc.
Sacrificial Protection –
The metallic iron is covered by a layer of more reactive metal such as
zinc. The active metal losses electrons in preference of iron. Thus,
protecting from rusting and corrosion.
Electrical Protection –
The metallic iron is connected with more active metals like
magnesium or zinc. The active metal has lower reduction potential
than iron and will lose electron in preference to iron,
This method is used for protecting iron articles which are in contact
with water.
Anti-Rust Solution –
To retard the corrosion of iron, certain anti-rust solutions are used .
example – alkaline phosphate and alkaline chromates.

8. Aim
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
aluminum rusting is prevented but if on the
other hand , it is coupled with less electro –
positive metals like copper , the rusting is
facilitated.

9. Materials Required
1)Two Petri dishes
2) Four iron nails
3) Beaker
4) Sand paper
5) Wire gauge
6) Gelatin
7) Copper, zinc & magnesium strips
8) Potassium ferricyanide solution
9) Phenolphthalein
10) Bunsen Burner

11. 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 & 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.
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 .Covered
Petri dishes for one day or so.
4) 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 𝑲𝑭𝒆[𝑭𝒆(𝑪𝑵) 𝟔] where
pink patch is due to the formation of hydroxyl ions which turns colourless
phenolphthalein to pink.

14. Observation
S.No. Metal Pair Colour of
the patch
Nails Rust
1 Iron-Zinc Pink No
2 Iron-Magnesium Pink No
3 Iron-Copper Blue Yes
4 Iron-Nail Blue Yes

17. Associated reactions
The rusting of iron is an electrochemical process that begins with the
transfer of electrons from iron to oxygen. The iron is the reducing agent
(gives up electrons) while the oxygen is the oxidising agent (gains
electrons). The rate of corrosion is affected by water and accelerated
by electrolytes, as illustrated by the effects of road salt on the corrosion
of automobiles.
 The key reaction is the reduction of oxygen
𝑶 𝟐 + 𝟒𝒆− + 𝟐𝑯 𝟐 𝑶 ⟶ 𝟒𝑶𝑯−
Because it forms hydroxide ions, this process is strongly affected by the
presence of acid. Indeed, the corrosion of most metals by oxygen is
accelerated at low pH.
 Providing the electrons for the above reaction is the oxidation of
iron that may be described as follows:
𝑭𝒆 ⟶ 𝑭𝒆 𝟐+
+ 𝟐𝒆−
 The following redox reaction also occurs in the presence of water
and is crucial to the formation of rust:
𝟒𝑭𝒆 𝟐+
+ 𝑶 𝟐 ⟶ 𝟒𝑭𝒆 𝟑+
+ 𝟐𝑶 𝟐
−
 In addition, the following multistep acid-base reactions affect the
course of rust formation:
𝑭𝒆 𝟐+
+ 𝟐𝑯 𝟐 𝑶 ⟶ 𝑭𝒆(𝑶𝑯) 𝟐 + 𝟐𝑯+
𝑭𝒆 𝟑+
+ 𝟑𝑯 𝟐 𝑶 ⟶ 𝑭𝒆(𝑶𝑯) 𝟑 + 𝟑𝑯+

18. as do the following dehydration equilibria:
𝑭𝒆(𝑶𝑯) 𝟐 ⟶ 𝑭𝒆𝑶 + 𝑯 𝟐 𝑶
𝑭𝒆(𝑶𝑯) 𝟑 ⟶ 𝑭𝒆𝑶(𝑶𝑯) + 𝑯 𝟐 𝑶
𝟐𝑭𝒆𝑶(𝑶𝑯) ⟶ 𝑭𝒆 𝟐 𝑶 𝟑 + 𝑯 𝟐 𝑶
From the above equations, it is also seen that the corrosion products are
dictated by the availability of water and oxygen. With limited dissolved
oxygen, iron(II)-containing materials are favoured, including FeO and
black lodestone or magnetite(𝑭𝒆 𝟑 𝑶 𝟒). High oxygen concentrations
favour ferric materials with the nominal formulae 𝑭𝒆(𝑶𝑯) 𝟑 − 𝒙𝑶 𝒙/𝟐.
The nature of rust changes with time, reflecting the slow rates of the
reactions of solids.
Furthermore, these complex processes are affected by the presence of
other ions, such as 𝑪𝒂 𝟐+, both of which serve as an electrolyte, and thus
accelerate rust formation, or combine with the hydroxides and oxides of
iron to precipitate a variety of Ca-Fe-O-OH species.
Onset of rusting can also be detected in laboratory with the use
of ferroxyl indicator solution. The solution detects both 𝑭𝒆 𝟐+ ions and
hydroxyl ions. Formation of Fe2+ ions and hydroxyl ions are indicated by
blue and pink patches
respectively.

19. 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.

20. Bibliography
1. www.en.wikipedia.org/wiki/Rust
2. www.class12guide.wordpress.com
3. www.academia.edu/Metal_Coupling
4. NCERT Chemistry Textbook for XII
5. Comprehensive (Practical Chemistry – XII)