New
New
Year 11
Edexcel
Higher

Corrosion and its prevention: including half equations

I can describe corrosion in detail, including chemical equations, and describe what actions can be taken to prevent corrosion.

New
New
Year 11
Edexcel
Higher

Corrosion and its prevention: including half equations

I can describe corrosion in detail, including chemical equations, and describe what actions can be taken to prevent corrosion.

Lesson details

Key learning points

  1. Corrosion is a general process of degradation of metals through various causes.
  2. Rusting is a specific type of corrosion, affecting iron in the presence of air and moisture.
  3. A metal oxide layer can protect the underlying metal if the oxide forms a physical barrier.
  4. Some coatings are reactive and contain a more reactive metal to provide sacrificial protection, e.g. zinc to galvanise.
  5. Electroplating can be used to improve the appearance and/or the resistance to corrosion of metal objects.

Common misconception

Students often believe rusting refers to the oxidation of any metal, and that corrosion is linked to the hazard 'corrosive'.

Highlight the conditions required for rusting, and the general description of corrosion.

Keywords

  • Rusting - The corrosion of iron or steel, in the presence of water and oxygen.

  • Corrosion - The gradual deterioration of a substance when it reacts with substances in the environment, for example when a metal oxidises in air.

  • Sacrificial protection - Using a more reactive metal to corrode preferentially, to protect another metal from corrosion.

  • Tarnishing - The process by which a thin, discoloured layer forms on the surface of a metal due to reactions with the environment, e.g. oxidation.

  • Electroplating - A process that uses electricity to deposit a thin layer of metal onto the surface of another conductive object.

A demonstration of the ways corrosion of metals can be limited (specifically iron and rusting) would be good to see, but may take time to set up. Really emphasise the key differences and similarities between the key words.
Teacher tip

Equipment

None required.

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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6 Questions

Q1.
Transition metals like copper and zinc are used in electrical applications because they are excellent of electricity.
Correct Answer: conductors
Q2.
When a metal reacts with oxygen, it often forms a .
Correct Answer: metal oxide, oxide, oxide product
Q3.
A is formed when two or more elements are chemically bonded together.
Correct Answer: compound
Q4.
Arrange the following metals in order of increasing reactivity with oxygen (most reactive at the top of the list).
1 - potassium
2 - zinc
3 - iron
4 - silver
5 - gold
Q5.
Which of the following reactions represents oxidation?
Cu²⁺ + 2e⁻ → Cu
Correct answer: Zn → Zn²⁺ + 2e⁻
H₂ + Cl₂ → 2HCl
NaCl → Na⁺ + Cl⁻
Q6.
The reactivity of a metal is linked to its ability to .
Correct Answer: lose electrons, oxidise

6 Questions

Q1.
What is sacrificial protection?
Painting a metal to prevent corrosion.
Correct answer: Using a more reactive metal to corrode preferentially and protect another metal.
Covering a metal with plastic to prevent air exposure.
Cleaning a metal regularly to prevent tarnishing.
Q2.
Which metal is often used to galvanise iron?
copper
Correct answer: zinc
silver
gold
Q3.
Which process involves the use of electricity to prevent corrosion and improve appearance?
galvanising
Correct answer: electroplating
anodising
alloying
Q4.
Rusting is a specific type of corrosion affecting in the presence of water and oxygen.
Correct Answer: iron, steel
Q5.
Complete the word equation for the rusting of iron. iron + → (hydrated) iron(Ⅲ) oxide
Correct Answer: oxygen + water, water + oxygen
Q6.
Which of the following equations is not involved in the rusting process?
O₂ (g) + 2H₂O(l) + 4e⁻ → 4OH⁻(aq)
Fe(s) → Fe²⁺(aq) + 2e⁻
Fe²⁺(aq) + 2OH⁻(aq) → Fe(OH)₂ (s)
Correct answer: 2Fe + O₂ → 2FeO
4Fe(OH)₂ (s) + O₂ (g) → 2Fe₂O₃·H₂O(s) + 2H₂O(l)