Cathodic protection.
The use of finishes · Technical principles
Revision notes
Cathodic protection
Cathodic protection is used to reduce corrosion of metals, particularly steel structures exposed to water or soil, such as pipelines, tanks, ships and offshore structures.
A more reactive metal can be connected to the steel. This sacrificial metal corrodes preferentially, helping protect the main steel structure. Zinc or magnesium may be used as sacrificial materials depending on the application.
Another method is impressed-current cathodic protection, where an external electrical system supplies the protective current. This is useful for large structures but needs power, monitoring and maintenance.
Why a designer might choose it
Cathodic protection can extend product or infrastructure life where ordinary paint or coating may be damaged or difficult to maintain. However, it adds components, installation cost and maintenance requirements.
Useful comparison
A coating such as paint or galvanising creates a protective barrier at the surface. Cathodic protection uses an electrochemical method to reduce corrosion and can continue protecting exposed areas when correctly designed.
For an exam answer, link the method to the environment and product life rather than simply stating that it ‘stops rust’.
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