Rust forms when iron, oxygen, and water meet at the same time, which is why keeping any one of the three away stops the reaction. Paint and oil keep water and oxygen off the metal surface. Galvanizing coats steel in zinc, a metal that corrodes in preference to the iron beneath it, so the zinc sacrifices itself first. In dry climates, iron can sit exposed for decades with barely a mark, which surprises people who assume rust is simply what old metal does. It is not age that causes rust. It is the presence of water.
It can be inferred that galvanizing protects steel by
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Correct answer to question 66 (Paragraph Comprehension): corroding before the steel underneath does
Method
The passage says zinc corrodes in preference to the iron beneath it and sacrifices itself first, so the coating protects the steel by rusting in its place.
Updated: November 2026
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