Corrosion
Corrosion is the slow damage of a metal by air, moisture, or other substances around it.
Practice This ConceptMain explanation
Teacher explanation
In iron, corrosion commonly appears as rusting. Air supplies oxygen and moisture helps the reaction continue. Because it is slow, students often notice corrosion only after the metal has already started weakening.
Example
An iron gate left outdoors in rainy weather rusts faster.
Simple analogy
Rust grows where air meets water.
Common confusion
Students often mention only air or only water. For iron, both air and moisture are important.
Exam tip
If the question asks why rusting speeds up, mention both air and moisture clearly.
Answer writing and exam use
1-mark use
Write the exact meaning of corrosion in one clean line.
2-mark use
Define corrosion and add one example or condition.
3-mark use
Explain corrosion, show the method or example, and mention the common mistake.
Practice this concept with focused MCQs
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