The document discusses various concepts related to corrosion and electrochemistry, including the definitions of cathode and anode, electrochemical cells versus electrolytic cells, and the electrochemical series. It elaborates on different types of corrosion such as galvanic, concentration, and pitting corrosion, as well as methods for protection against corrosion like sacrificial anodes and galvanization. Additionally, it highlights the importance of protective coatings and the process of tinning in corrosion prevention.

9. Difference Between Cathode and Anode

10. Difference Between Electrochemical Cell and Electrolytic Cell

11. Electrochemical Series
The arrangement of elements in order of increasing electrode
potential values is called “Electrochemical Series”.
The Electrochemical Series is also called “Activity Series”.
The series has been established by measuring the potential of
various electrodes versus standard hydrogen electrode (SHE).

21. Mechanism of Dry Corossion
-

22. Galvanic corrosion, also known as
bimetallic corrosion, is an electrochemical
process whereby one metal corrodes in
preference to another metal that it is in contact
with through an electrolyte. Galvanic
corrosion occurs when two dissimilar metals
are immersed in a conductive solution and are
electrically connected.
Galvanic Corrosion

24. Concentration Corrosion
It is due to the electrochemical attack on metal surface, exposed
to an electrolyte of varying concentrations or of varying aeration.
It occurs when one part of metal is exposed to a different air
concentration from the other part.
This causes a difference in potential difference between
differently aerated areas. It has been found experimentally that
poor oxygenated parts are anodic.

25. Pitting Corrosion
Pitting corrosion is very localized form of corrosion, which causes
small holes in the metal affected. Pitting corrosion can be started
by a small scratch or damage to a protective coating.
Pitting is more common in alloys that are protected against
corrosion by using a passivation layer. These include stainless
steel, Nickel alloys and Aluminium alloys etc.
Pitting corrosion is a localized form of corrosion by which
cavities or holes are produced in the material. Pitting is
considered to be more dangerous than uniform corrosion damage
because it is more difficult to detect, predict and design.

26. Different Types of Pitting Corrosion

27. 1 2
3 4

28. Protection from Corrosion

29. Protection from corrosion by protective coatings

33. 1
2
3
4

36. It is also called “Sacrificial Protection”. Because oxidation potential of Zinc (Zn) is
higher than the oxidation potential of Iron (Fe).
Hence, oxidation of Zinc (Zn) occurs first and iron (Fe) will be protected.
Galvanization: Electroplating of Zinc

39. Application and Uses of Galvanization:-
There are a number of uses for zinc, with zinc metal being the largest and most
common. In fact, fifty percent of the annual production, or approximately 5.5
million tons of zinc, is used for galvanizing to protect steel from corrosion.

41. Similarly, Tin (Sn) coating is called “Tinning”.
Tinning is the process of thinly coating sheets of
wrought iron or steel with tin, and the resulting
product is known as tinplate.

42. Cathodic Protection: Sacrificial Anode
Protection of metal from corrosion by connecting it with a more active metal (i.e.
more anodic metal e.g. Mg, Al etc.)
The connected active metal undergoes corrosion, thereby protecting the parental
metal from corrosion.

45. Modifications in Design