Chapter 16.3 - Corrosion

Question 1

Define ‘dry corrosion’/’direct corrosion’.

Answer 1

A direct reaction with oxygen in the air to form a metal oxide.

Question 2

Define ‘wet corrosion’.

Answer 2

A reaction where the presence of moisture accelerates the corrosion of a metal.

Question 3

State the circumstances in which wet corrosion can occur.

Answer 3

In moist air or by direct immersion in water.

Question 4

State what corrosion can be accelerated by.

Answer 4

1. The presence of moisture.

2. Impurities. e.g Salt and acidic pollutants which dissolve in water.

Question 5

State the two ways of preventing corrosion.

Answer 5

1. Surface protection.

2. Electrochemical protection.

Question 6

Describe ‘surface protection’.

Answer 6

The covering of a metal’s surface in order to prevent contact with oxygen and moisture.

Question 7

State different materials used for ‘surface protection’.

Answer 7

1. Paint.
2. Plastic.
3. Oil/Grease.

Question 8

State how surface protection can occur without the physical act of covering a metal with a material.

Answer 8

Alloying (mixing metals) with small quantities of metals can produce stainless metals. E.g iron to stainless steel.

Metal can also be coated with thin layers of less reactive metals in a process known as electroplating.