Transcript of "Cathodic Protection Technique to Control Galvanic Corrosion"
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
SUBMITTED TO: DR/ MOHAMED
- 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.
A process that degrades metals electrochemically. It
occurs in two cases.
Case I (Corrosion occurs between two
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.
What happens inside the galvanic cell?
Zinc atoms are losing two electrons, forming Zinc ions (Zn⁺⁺) which enter the
The two electrons (e⁻) lost by Zinc metal flow through the wire to the copper
Two electrons (e⁻)
combine with each
cupper ion (Cu⁺⁺) in the
solution to produce
- 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.
The impact of corrosion on structure
1- Sacrificial Anode
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
1- SACRIFICIAL ANODE
A piece of more active metal is attached to the
vulnerable “less active” where it is exposed to the
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.
1- Sacrificial Anode
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
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.
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