Aluminium does not rust like iron because it forms a protective oxide layer (Al₂O₃) that prevents further corrosion. Its dull appearance can be prevented by polishing or anodizing, which maintains shine. Aluminium is preferred for roofing because it is lightweight, corrosion-resistant, durable and requires less maintenance, making it more suitable than iron sheets.
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(i) Aluminium forms a thin protective oxide layer (Al₂O₃) on its surface when exposed to air. This layer prevents further corrosion, unlike iron which forms rust (Fe₂O₃·xH₂O) that flakes off.
(ii) The dull appearance can be prevented by polishing or anodizing the aluminium surface to maintain its shine and protect it from corrosion.
(iii) Aluminium is lightweight, corrosion-resistant, and durable, making it ideal for roofing, whereas iron sheets are heavier and prone to rusting, requiring more maintenance.