FACULTY OF SCINCE AND ENGINEERINGSCHOOL OF PETROLEUM AND CHEMISTRY PETROLEUM DEPARTMENT Third stage

(Overview of Galvanic Corrosion) Prepared by : Kamal AbdurahmanSupervised by: Dr.Nabil 

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

Example corrosion

Example #2

Result of Galvanic Corrosion

Corrosion forms

• 1-Uniform corrosion • 2-Galvanic corrosion

• In this presentation we explain the second form of corrosion which is

• Galvanic corrosion

2. Galvanic Corrosion

Video of Galvanic corrosion Procedure

• 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.

Attractive Video

• 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

Example#2: Storage Tanks

Prevention of Galvanic Corrosion:

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

Galvanic Metallic Coatings

Example#1: Galvanized Steel

Example#2: Tinned Steel Cans

Questions?

Thank you for your attention