1. What condition is essential for galvanic (bimetallic) corrosion to occur?
Oxygen; electrolyte; (two metals having) different potentials
2. How do we recognize turbulence corrosion?
In copper we can find sharply defined pits which commonly are undercut on the side facing the water’s direction of flow
3. When we use the term degraphitation of cast iron, what kind of corrosion do we refer to ?
Selective corrosion
4. Degraphitation is a special form of bimetallic corrosion and either iron or the steel is consumed
through dissolution. Which of the two substances will go to dissolution?
Iron (will sacrifice itself for graphite leaving the surface as a layer. This layer has no
mechanical strength, however the object looks intact. The graphite may be easily removed with
e.g. a knife.
5. Most of coatings function by the barrier principal. Against what is the coating barrier?
(against) liquid; water and partly oxygen
6. Dose a coating heavily pigmented with zinc phosphate provide corrosion protection by the
galvanic principle?
No, by inhibitor principle
