Corrosion is the degradation of metal. In this EEI the corrosion of tin cans will be looked at, in more detail the galvanic corrosion of Fe in a Fe and Sn galvanic cell.
The most common from of rust that we encounter is Iron rust. This is a result of the Fe metal oxidising as seen in these half reactions both for Iron 1 and Iron 2.
Fe(s) → Fe2+(aq)
+ 2e-
Fe2+→ Fe3+
+ e-
The second half reaction containing Iron 2 is because the Fe3+ ion is the ion in Fe2O3 and Fe2O3 is the hydrated iron oxide with H2O.
Therefore if the more easily the metal is oxidised the higher its corrosion rate will be.
Facts about rusting
(taken from the Chemistry in Use Book 2 p372)
(taken from the Chemistry in Use Book 2 p372)
1. Both oxygen and water are necessary for rust to form.
2. Salt water accelerates rusting.
3. Impure iron rusts more rapidly that pure iron.
4. Iron rusts more rapidly when attached to a less reactive metal such as Cu or Sn when on its own (the EEI being conducted involves Fe in Contact with Sn)
4. Iron rusts more rapidly when attached to a less reactive metal such as Cu or Sn when on its own (the EEI being conducted involves Fe in Contact with Sn)
5. Rust occurs most readily where iron is under mechanical stress-at bends in sheets, points of nails, sharp edges of knives and razor blades, and around bolts and rivets under tension.
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