Advanced Corrosion

Question 1

Describe Passivation?

Answer 1

Passivation is the formation of a protective oxide film on the surface reducing its chemical activity and its ability to corrode

Question 2

Describe the following factors and how they affect corrosion:
Oxygen-
Temperature-
Chemical salts-
Humidity (or wetness)-
Pollutants and acid gases-

Answer 2

Oxygen- increases the rate of corrosion
Temperature-Corrosion usually accelerated with increasing temperature
Chemical Salts-Increase the rate of corrosion bu increasing the efficiency of the electrolyte
Humidity(or wetness) - The wetter the environment the more corrosion is likely to occur
Pollutants and acid gases- Acid rain, chemical byproducts and chlorides all promote corrosion

Question 3

Two broad categories of corrosion?

Answer 3

General

Localised

Question 4

Describe galvanic corrosion?

Answer 4

An electrochemical action of two dissimilar metals in the presence of an electrolyte and an electron conductive path, which occurs when dissimilar metals come into contact

Question 5

Describe cathodic protection?

Answer 5

Cathodic protection is the reduction or elimination of corrosion by making the structure to be protected a cathode by means of an impressed current or attachment to a galvanic anode.

Question 6

The two primary types of cathodic protection are?

Answer 6

Impressed current

Galvanic (sacrificial)

Question 7

Impressed current power sources include?

Answer 7

Rectified commercial power
Solar Cells
Generators
Fuel Cells
Wind-powered cells
Thermoelectric cells

Question 8

Describe cathodic disbondment?

Answer 8

Cathodic disbondment is the separation of the coating from the surface through hydroxyl (OH-) formation due to increased (made more negative) potential