Rust
Rust is iron oxide — a chemical compound formed when iron meets oxygen and water. It forms an ionic bond with fabric fibres. Acids (citric, oxalic) break this bond by dissolving the iron oxide.
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Frequently asked questions
Why does bleach make rust worse?
Bleach oxidises the iron in rust further and permanently bonds the orange colour to fabric fibres. It makes the stain darker and fully permanent.
How does lemon juice remove rust?
Citric acid in lemon juice reacts with iron oxide (rust), converting it to a water-soluble iron citrate compound that can be rinsed away.