Why does metal rust?
Show answer & explanation
Answer: Iron reacts with oxygen
Iron reacts with oxygen ✓ — Correct! Rust is iron oxide (Fe₂O₃). Iron reacts with oxygen in the presence of water (electrolyte): 4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃, which dehydrates to rust. This is oxidation—iron loses electrons. Rust is porous, allowing further corrosion. Prevention: paint, galvanization (zinc coating), stainless steel (chromium prevents oxidation). Only iron and its alloys rust specifically!
Temperature changes metal — Wrong. Temperature can accelerate reactions, but rust is specifically iron oxidation—chemical reaction between iron, oxygen, and water.
Dirt corrodes the surface — Wrong. Dirt doesn't cause rust—it's oxidation. Iron reacts with oxygen in the presence of water, forming iron oxide (rust).