What is galvanisation? Why does a galvanised iron article remain protected against rusting even if its zinc coating is scratched?
Generated by claude-sonnet-4-6 · 2026-06-26 01:05 · grounding rag
Model Answer
Galvanisation is a method of protecting iron and steel from rusting by coating them with a thin layer of zinc.
Even if the zinc coating is scratched, the iron beneath remains protected because zinc is more reactive than iron. Zinc corrodes preferentially (acts as a sacrificial metal), thereby preventing iron from rusting.
Source: Chapter 3, Section 3.5.1 – Prevention of Corrosion
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Explanation
- Part 1 (definition) fetches 1 mark — state it concisely.
- Part 2 (reason) fetches the other 1 mark — the key idea is that zinc is more reactive than iron, so it oxidises first and protects iron even when the coating is broken. Examiners look for the phrase "more reactive" or "sacrificial protection." Don't just say "zinc forms a protective layer" — that only explains unscratched coating.