Chapter 2 - Corrosion, Decay and Degradation

Question 1

Rust

Answer 1

The oxidation of steels (not stainless steel) due to contact with the air that may well contain moisture. The oxide layer of steels is porous, so further oxidation can take place. This results in a thicker oxide layer as the material breaks down.

Question 2

Electrochemical cell

Answer 2

The term given to the conditions necessary to promote corrosion between two different metals. The additional component is an electrolyte e.g. Rainwater containing salts and acids.

Question 3

Wet rot

Answer 3

Decay in woods that is a direct result of alternating cycles of the timber being wet, followed by drying i.e. an accumulation of moisture that breaks down the cellular structure

Question 4

Dry Rot

Answer 4

A fungal attack, causing a breakdown of lignin resins that hold the cellular structure of the material together. The fungus is Merulius lacrymans and is usually present in dry, unventilated areas. The strands of the fungus can also penetrate brickwork, enabling it to travel quickly through a building

Question 5

Woodworm

Answer 5

An insect that attacks both hardwood and softwood by laying eggs in crevices in the material. The larvae eat away at the timber, then emerge through flight holes ? the tell-tale signs of wood work infestation.