Corrosion of Metals Flashcards
All 6 cards in this deck
What happens to a metal when it corrodes?
The metal is oxidised (it reacts with oxygen to form an oxide).
True or false? Iron will rust if it is left in completely dry air.
False. Both oxygen (air) and water are needed for iron to rust.
Name three barrier methods used to prevent iron rusting, and say how a barrier works.
Painting, oiling/greasing and coating with plastic; the barrier excludes oxygen and water from the iron surface.
How does sacrificial protection stop iron from rusting?
e.g. iron galvanised with a layer of zinc
A more reactive metal is oxidised in preference to the iron; the zinc corrodes instead of the iron because zinc is more reactive than iron.
Give two reasons why a metal object is electroplated with gold.
To improve its appearance and to increase its resistance to corrosion.
What are the steps to set up the electroplating of a metal object?
e.g. plating a steel spoon with silver
- Object = negative electrode (cathode): the steel spoon.
- Plating metal = positive electrode (anode): silver.
- Electrolyte = solution of a salt of the plating metal: silver nitrate solution.