C13 Corrosion Of Metals

Question 1

Corrosion

Answer 1

• Corrosion is the process of oxidation of a metal, caused by oxygen in the atmosphere. For some metals it is very easy (sodium or lithium) for some it is very very hard (gold or platinum).
• This links with the reactivity series.
• Corrosion of iron and steel (made mostly of iron) is called rusting.

Question 2

Tarnishing

Answer 2

• Middle reactivity metals undergo tarnishing commonly silver, copper, aluminium.
• This is when the outer layer of the metal oxidises, producing a protective layer of metal oxide. The coating stops oxygen from getting to the pure metal underneath.
• Copper’s oxide is know as Verdigris and it is why copper statue of liberty looks green.

Question 3

Oxidation

Answer 3

Oxidation is the loss of electrons.
• Most corrosion/ tarnishing in metals is due to a reaction with oxygen but it can also be due to a reaction with other substances found in air.
• Silver reacts with hydrogen sulfide to produce a black solid called silver sulphide.

Question 4

Rusting

Answer 4

• When corrosion continues (doesn’t just form a protective layer) the metal will breakdown over time.
• Rusting is corrosions of iron or steel (mostly iron).
• Rust is the brow flaky substance, as it flakes off it exposes more fresh iron/ steel to oxidation, corroding and weakening the metal.