Distinguish between galvanizing and tinning.
Q.1 (b) Distinguish between galvanizing and tinning.
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| Galvanizing | Tinning |
|---|---|
| Iron or steel is coated with zinc, usually by dipping in molten Zn at about 450 °C. | Iron or steel is coated with tin, usually by dipping in molten Sn at about 232–250 °C. |
| Zn is more electropositive (more anodic) than Fe, so it is an anodic coating. | Sn is less electropositive (more cathodic, more noble) than Fe, so it is a cathodic coating. |
| Zn protects Fe sacrificially. Even if the coating is broken, Fe is still protected because Zn corrodes instead. | Sn protects Fe only while the coating is unbroken. If it is scratched, Fe becomes the anode with a small area and a large cathode, so pitting is rapid. |
| Galvanized vessels are not used for food, because Zn dissolves in dilute food acids to give toxic compounds. | Tinned containers are used for food storage, because Sn is non-toxic. |
| Uses: roofing sheets, buckets, pipes, wires, nuts and bolts. | Uses: food cans, copper utensils, refrigeration equipment. |
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· 25 Oct 2026
AI-verified · Oct 2026
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