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ENGINEERING, CS 2025 HSC 11 MC

Which of the following is true of cathodic protection?

  1. It uses high temperatures to preserve metals.
  2. It uses a polymer coating to prevent corrosion.
  3. It uses heat treatment to improve the tensile strength.
  4. It uses an electric current to prevent corrosion of metals.
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\(D\)

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  • Cathodic protection works by supplying an electric current that makes the metal structure the cathode, preventing oxidation (corrosion).
  • \(\text{A}\) is incorrect — high temperatures accelerate corrosion rather than prevent it.
  • \(\text{B}\) describes paint/polymer coating — a separate corrosion prevention method, not cathodic protection.
  • \(\text{C}\) describes heat treatment — a process that changes mechanical properties, unrelated to corrosion prevention.

\(\Rightarrow D\)

ENGINEERING, CS 2024 HSC 27a

A towbar hitch and shear pin is shown.

The hitch is exposed to various environmental conditions.

Outline a method to protect against corrosion.   (2 marks)

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  • Applying protective finishes like paint or powder coating provides a barrier that shields the component from corrosive elements.
  • This resistance is a result of preventing the hitch from exposure to oxygen, moisture, and environmental contaminants.

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  • Applying protective finishes like paint or powder coating provides a barrier that shields the component from corrosive elements.
  • This resistance is a result of preventing the hitch from exposure to oxygen, moisture, and environmental contaminants.

ENGINEERING, CS 2020 HSC 26a

Describe methods used to protect civil structures against corrosion. Support your answer with examples.   (3 marks)

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  • The use of sacrificial anodes. For example a block of zinc can be connected to a civil structure so any corrosion occurs at this anode.
  • Surface coating such as organic based paints or salt films can protect the surface of the metal structure.

Other examples could include:

  • Galvanic protection.
  • Ceramic coating or oxide films.
Show Worked Solution
  • The use of sacrificial anodes. For example a block of zinc can be connected to a civil structure so any corrosion occurs at this anode.
  • Surface coating such as organic based paints or salt films can protect the surface of the metal structure.

Other examples could include:

  • Galvanic protection.
  • Ceramic coating or oxide films.

ENGINEERING, CS 2021 HSC 20 MC

The galvanic table below shows the relative corrosion potential of a metal when it is in contact with another metal in an aqueous environment.
 

In which of the following situations is the steel component likely to corrode in the shortest amount of time?
 

 

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`D`

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Two key factors affecting the rate of corrosion:

  • First is the difference in reactivity. Since the difference between steel and copper is greater than the difference between steel and aluminium, the answer must be `C` or `D`.
  • Secondly, the reaction is faster if the anode is smaller than the cathode. Therefore the steel must be the rivet, not the sheet.

`=>D`

♦ Mean mark 38%.