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Why can a layer of paint not protect an iron article from rusting permanently?
AA scratch lets air reach the bare metal
BPaint chemically reacts with the iron
CPaint dissolves the protective oxide layer
DPaint attracts more moisture to the iron
Answer & Solution
Correct answer: A. A scratch lets air reach the bare metal
1. Painting isolates the metal from air and moisture for a while.
2. If the paint gets scratched, a small bare surface of iron is exposed.
3. Air and moisture then reach this exposed metal and rusting starts beneath the paint.
4. The paint does not react with or dissolve into the iron, so those options are wrong.
_Source: Balbharati (Maharashtra Board) Class 10 Science & Technology, Ch 8 "Metallurgy", p.116_
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