Cathodic Protection Technique to Control Galvanic Corrosion Problem.

1. SUBMITTED BY
Mahmoud Saleh Elkaffas
 Ahmed Shawky Said
 Waleed Mohamed Awny
 Abdelhamid Saleh Abdelhamid
 Mohamed Mamdouh Ahmed
 Ahmed Nagdy Arafa
 Marwan Ahmed Abou-Salem
 Omar Mahmoud Moustafa
 Mahmoud El-Sayed Mahmoud
 Mohamed Nabil Zein El-din


2. SAFETY OF
ELECTROMECHANICAL
SYSTEMS
SUBMITTED TO: DR/ MOHAMED
MOHAMED ZAKARIA
Cathodic Protection

3. Introduction
- Corrosion is a process of formation of the compound of pure metal by the
chemical reaction between metallic surface and its environment.
-It is an oxidation process. -It causes loss of metal. - Hence, disintegration of a metal by its surrounding chemicals through
a chemical reaction on the surface of the metal is called corrosion.

4. Galvanic Corrosion
(Electrochemical
Corrosion)
A process that degrades metals electrochemically. It
occurs in two cases.
Case I
Occurs
between two
dissimilar
metals
Case II
Occurs between
same metals
exposed to
electrolyte with
different
concentrations

5. Case I (Corrosion occurs between two
dissimilar metals)
In a galvanic cell, the more active
metal (the anode) corrodes at an
accelerated rate and the more
noble metal (the cathode)
corrodes at a retarded rate.

6. What happens inside the galvanic cell?
Zinc atoms are losing two electrons, forming Zinc ions (Zn⁺⁺) which enter the
solution.
The two electrons (e⁻) lost by Zinc metal flow through the wire to the copper
electrode

7. Two electrons (e⁻)
combine with each
cupper ion (Cu⁺⁺) in the
solution to produce
cupper metal.

8. Galvanic Series
- The galvanic series (or electro potential series) determines the nobility
of metals and semi-metals. When two metals are submerged in an
electrolyte, while electrically connected, the less noble (base) will
experience galvanic corrosion. The rate of corrosion is determined by the
electrolyte and the difference in nobility.

9. Case II (Corrosion occurs between same metals)

11. What happens at the anode part?

12. What happens at the cathode part?

13. The end of the corrosion process on the pipeline. (WatchVideo:
http://www.youtube.com/watch?v=hfmD1RyUWgY)

14. Causes and Effects of Corrosion
The impact of corrosion on pipelines

18. (Video: http://www.youtube.com/watch?v=zeNtWvsmXAY)

19. The impact of corrosion on structure
(Video:http://www.youtube.com/watch?v=JweyK4rs6TE)

20. Cathodic
Protection
1- Sacrificial Anode
2- Impressed
Current

21. WHAT IS CATHODIC PROTECTION?
CP is a technique used to control 
the corrosion of a metal surface.
The principle of CP is to prevent 
anodic sites occurring on the
structure under protection by
allowing the anodic reactions to
occur on specially designed and
installed anodes.

22. 1- SACRIFICIAL ANODE
 A piece of more active metal is attached to the
vulnerable “less active” where it is exposed to the
corrosive liquid.
 Metals like (Zn, Mg, Al) are used for making
anode because they are more active “low
electrochemical potential” as compared to steel.
 When it is consumed completely, it will be
replaced by a newer one.

24. How the sacrificial anode works?

25. What happens at both the cathode and the anode?

26. (Video: http://www.youtube.com/watch?v=RAlC75xG4qU)

27. Cathodic
Protection
1- Sacrificial Anode
2- Impressed
Current

28. 2- IMPRESSED CURRENT
 For larger structures, sacrificial anode type can
not economically deliver enough current to
provide complete protection.
 An impressed current is applied in opposite
direction to nullify the corrosion current and
convert the corroding metal from anode into
cathode.
 ICCP systems are rectifiers which are connected
to an AC supply source and convert it into DC.
 In ICCP, the impressed current is given to
insoluble anode like graphite, stainless steel or
scrap iron buried in soil.

29. How the ICCP works?

31. (Video: http://www.youtube.com/watch?v=QYd9ENn1nP0 )

32. When to use ICCP?
Stray current: is a flow of electricity through equipment, buildings
or the ground due to imbalances in electrical supply systems or
because of wiring damage. It may cause electrochemical
corrosion.

36. (Video: http://www.youtube.com/watch?v=fUv9eGp5AUM)

37. When to use sacrificial anode cathodic protection?

39. (Video: http://www.youtube.com/watch?v=9I5tMKqFXXo)

40. ANY QUESTIONS ?

41. References:
http://www.youtube.com/user/CorrConnect/videos
 http://www.slideshare.net/abhishekwantsyou/cathodi
c-protection-14917643?from_search=1
 http://www.mhhe.com/physsci/chemistry/essentialch
emistry/flash/galvan5.swf
