GCSE Chemistry · Edexcel 1CH0 · Topic 5A
Transition metals, alloys and corrosion
Key points
- Transition metals (the central block) have high melting points and high densities, form coloured compounds and often act as catalysts, e.g. iron in the Haber process.
- Corrosion is the oxidation of a metal. Rusting needs both oxygen and water: iron + oxygen + water → hydrated iron(III) oxide.
- Prevention: a barrier (paint, oil, grease, plastic); galvanising (coating with zinc); sacrificial protection (attaching a more reactive metal that corrodes instead).
- Electroplating uses electrolysis to coat an object with a thin layer of another metal for appearance or corrosion resistance; the object is the cathode.
- Alloys are mixtures of a metal with other elements. Different-sized atoms disrupt the layers so they cannot slide easily, making alloys harder. Examples: steel, brass, gold alloys (carats), aluminium alloys for aircraft.
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Transition metals such as iron, copper and chromium are among the most useful materials we have, but many corrode. These notes cover their properties, rusting and its prevention, electroplating and alloys.
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