STUDY OF THE EFFECT OF METAL COUPLING ON THE RUSTING OF IRON

PRESENTED BY

NAME: SANJAY PS

CLASS: XII-A

YEAR: 2015-2016

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

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:

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

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

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

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.

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

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

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.

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, 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

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

losses electrons in preference of iron.

Thus, protecting from rusting and

corrosion.

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.

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

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.

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.

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.

OBSERVATION

S.No Metal Pair Colour

of the

patch

Nails

rusts or

not

1 Iron-Zinc

2 Iron-

Magnesium

3 Iron-

Copper

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.

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