This document provides an overview of galvanic corrosion. It defines corrosion and galvanic corrosion specifically. Galvanic corrosion occurs when two dissimilar metals are in contact, where the more active metal corrodes at an accelerated rate while the noble metal corrodes at a reduced rate. The document highlights how the difference in corrosion potentials between the metals determines the severity of galvanic corrosion. It also notes some methods to prevent galvanic corrosion, such as using galvanic coatings and controlling the surface area ratio between the metals. Videos are included to demonstrate galvanic corrosion procedures and examples.

1. FACULTY OF SCINCE AND ENGINEERING
SCHOOL OF PETROLEUM AND CHEMISTRY
PETROLEUM DEPARTMENT
Third stage
(Overview of Galvanic Corrosion)
Prepared by :
Kamal Abdurahman
Supervised by:
Dr.Nabil

2. Definition
• Corrosion may be defined as the destruction of a
metal or an alloy because of chemical or
electrochemical reaction with it's surrounding
enviroment or medium

3. Example corrosion

4. Example #2

5. Result of GalvanicCorrosion

6. Corrosion forms
• 1-Uniform corrosion
• 2-Galvanic corrosion
• In this presentation we explain the
second form of corrosion which is
• Galvanic corrosion

7. 2. Galvanic Corrosion

8. Video of Galvanic corrosion Procedure

9. • When two dissimilar metals are in contact, the
corrosion rate of the more active metal(more
negative Ecorr) is accelerated, while the
corrosion rate of the noble metal(less negative
Ecorr) is reduced.
• •The higher the difference in Ecorr, the more
severe is galvanic corrosion.
• •Galvanic Series: a list of measured corrosion
potentials (Ecorr) of a number of metals and
alloys in a given electrolyte.

11. Attractive Video

12. • Area effects:
• –IC= Ia(total current in amps)
• –ic*Ac= ia* Aa(i in amp/cm2)
• –or ia∝Ac/Aa(proportional to galvanic corrosion damage)
• –High Ac/Aaleads to high ia(bad from GC viewpoint)
• –Example: integrity of mechanical fasteners
• •Riveted plates of Cu and steel.
• •Painted steel storage tank

15. Example#2: Storage Tanks

16. Prevention of Galvanic Corrosion:

17. Kinetics of GC: 1-Corroding metal-inert
metal couple

18. Galvanic Metallic Coatings

19. Example#1: Galvanized Steel

20. Example#2: Tinned Steel Cans

23. Questions?