A thorough insight into corrosion control, its types, causes, measures to control along with case studies.

1. A Presentation by:
PSV
Narender
Pranjal
Ratan
Saurabh
Shakti
Shikhar
Sohan

2. Corrosion Fundamentals
 Corrosion can be defined as the degradation of a
material due to reaction with its environment.
 Corrosion is Extractive Metallurgy in reverse.
 It is a spontaneous process.
 The driving force of corrosion is the tendency of the
metals to have lower energy.

3. Why Corrosion Control?
 Economic Aspects: It can be referred to as
cost of corrosion under Direct Loss and
Indirect Loss.
 Health Aspects: Surgical instruments,
implants, pacemakers, etc. are all prone to
corrosion.
 Cultural Aspects: Antiques and Monuments may
get extinct due to corrosion.
 Safety Aspects: Machine parts in factories
and home appliances can cause harm if
corroded.

4. Prevention Measures
 Design Constraints
 Role of Materials
 Protective Coatings
 Cathodic Protection
 Environmental Modification
 Passivation

5. Design Constraints
 Design for proper drainage, less crevices, less stress,
less water retention.
 Design for allowances.

7. Role of Materials
 Use of pure metals: eg: Aluminium, Titanium ,Gold,
Platinum etc....
 Use of corrosion resistant alloys. eg:Duralumin, Stainless
steel, Brass, Bronze etc....
 Fulfill required functionality in terms of strength and
corrosion resistance.

8. Protective coatings
 Metal coating: Surface of a metal( base metal) is
coated with another metal(coat metal).
 Painting: A suitable top coat which excludes water
and oxygen from the surface.
 Polishing: Finely finishing the surface.

9. Metal Coating
 Hot Dipping: Base metal is dipped or passed through
molten coat metal or alloy.
Eg:Galvanization
 Metal Spraying: Coat metal is sprayed on base
metal.
 Cementation: Base metal is protected by alloying its
surface with another metal.

10. Metal Coating
 Metal Cladding: Base metal is sandwiched
between thin layers of hot metal and
pressed between rollers.
 Electroplating: Deposition of coat metal over
base metal using electricity.
 Anodising: Formation of hydrated oxide layer
of coat metal over base metal.

11. Painting
 Oil Painting: Most widely used consist of
pigments and thinners.
 Water Painting: A suspension of dispersible
pigments in emulsion of water and small
quantities of drying oils.
 Special Paints: Special chemicals are added in
paints specific purpose. Eg: Heat resistant
paints, water repellant paints, etc.

13. Cathodic Protection
 The metal to be protected is connected to an
external anode and a D.C. current is passed so that
all areas of the metal surface become cathodic and
do not corrode.
 Cathodic protection can be achieved in two ways:
1. By Sacrificial Anodes.
2. By Impressed Current.

14. Sacrificial Anodes
 These anodes consist of the highly reactive metal like
Mg.
 To protect pipes, rods of Mg buried near the pipes and
connected to them by wires.
 Thus Galvanic cells with high E.M.F are setup with
surface to be protected made cathodic.
 The cost of replacement of corroded anodic Mg is
much less than replacing pipes.

16. Impressed Current Method
 The object to be protected is made cathode of an
electrolytic cell by connecting it to negative terminal
of a D.C source.
 This is done by rectifying an A.C line or using D.C
source.
 The positive terminal is connected to scrap iron.

18. Environmental Modification
 Deaeration: Removal of dissolved oxygen. Eg:
By adding chemicals like Sodium Sulphite.
 Dehumidification: Removal of moisture from
air. Eg: By adding chemicals like Silica.
 Inhibitors: It is a chemical additive which
reduce the rate of corrosion. Eg: Alkali,
Amines, Orthophosphates, etc.

19.  It is using a light coat of material such as a metal oxide
to create a shell against corrosion. It can only occur in
certain conditions and is used in micro-electronics to
enhance silicon.

20. Case Study: Iron Pillar, Delhi
 The iron pillar of Delhi has not rusted from the
last 16 centuries due to the following reasons:

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21. Case Study: Eiffel Tower
 The structure comprises 220000 metre square of
surface (300 tonnes of wrought iron) that have to be
maintained and repainted every 7 years, consuming 50
tonnes of lead free paint.
 for renovation ,corroded areas are prepared before
painting.
 All this is carried out by around 25 painters, works
lasting for around 15 months and costing over
20 million francs.

22. Conclusion
Thus we understood the basics behind corrosion and its
aspects in practical life. We also looked at various
aspects of corrosion control along with 2 case studies.
Thus this presentation underlines the importance of
corrosion control and its significance for the model
world.

23. Reference
 Textbook of engineering chemistry by:- R Gopalan,
D Venkappayya, Sulochana Nagarajan.
 corrosion.ksc.nasa.org
 Lecture notes by Dr. K.G. Sreejalakshmi.
 Google.
 Wikipedia.