Shipwrecks and Salvage > 2. Corrosion of Iron >
Use available evidence to analyse and explain the conditions under which rusting occurs
| Condition: | Effect on Reaction: | Explanation: |
| Oxygen and water present | Allows reaction to take place | Oxygen and water are both necessary, as together they can be reduced to form hydroxide ions |
| Electrolyte present | Increases rate | Allows ions to move freely between the site of oxidation and the site of reduction |
| Impure iron | Increases rate | Impurities may act as the cathode |
| Iron in contact with less active metal | Increases rate | Less active metal serves as the cathode |
| Iron under mechanical stress | Increases rate | Individual iron atoms are less tightly bonded together and can more easily break away |