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A sacrificial anode protects iron because the anode metal has a reduction potential that is:
ALower than iron's
BHigher than iron's
CIdentical to iron's
DExactly equal to zero
Answer & Solution
Correct answer: A. Lower than iron's
1. Galvanising coats iron with zinc, but the coating can be breached by corrosion or abrasion.
2. Even then the iron may still be protected by a cathodic protection process.
3. The more active metals, those with lower reduction potential, are called sacrificial anodes.
4. They get used up as they corrode, that is oxidise, at the anode.
5. The iron survives because the more active metal is oxidised in its place.
_Source: OpenStax Chemistry 2e (CC BY 4.0), Ch 17 'Electrochemistry', sections 17.1-17.7_
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