Corrosion & Its Prevention Flashcards

All 6 cards in this deck

What is corrosion?

The destruction of materials by chemical reactions with substances in the environment.
e.g. rusting of iron is an example of corrosion.

Which two substances must both be present for iron to rust?

Air (oxygen) and water.
If either is missing, the iron does not rust.

What are the steps to set up an experiment to show that both air and water are needed for rusting?
e.g. an iron nail in each of three boiling tubes

1. Tube 1: nail in air and water — rusts.
2. Tube 2: nail in boiled water with a layer of oil on top (no air) — no rust.
3. Tube 3: nail in dry air with a drying agent such as calcium chloride — no rust.

Name three barrier methods of preventing corrosion.

Greasing (oiling), painting and electroplating.
They stop air and water reaching the metal.

Why do aluminium objects not need protecting from corrosion?

Aluminium has an oxide coating that acts as a barrier, preventing contact between the metal and air/water.

What is sacrificial protection?
e.g. galvanising iron by coating it with zinc

Coating the metal with a more reactive metal, which corrodes instead of the metal underneath.
Zinc is more reactive than iron, so the zinc corrodes and the iron is protected.