A 13 b Rust protection by tin and by zinc coating
 
 

Coating protects iron from rusting:

What is about rust protection after scratching of the coat?
* Left: Cut a piece of steel covered by zinc and a piece of steel from a milk can.
* Middle: Scratch the two samples and put them into 5-ml vials with water.
  Add drops of hydrochloric acid to speed up rusting.
  As an indicator for corroded iron particles add a drop of  K3[Fe(CN)6] solution.
Observation right: Only the tin sample is corroded resulting in a blue colour of the Fe2+indicator.


Zinc is a suitable coating substance for instance for the body of cars and other out-door products made of steel.
Tin is a suitable coating substance for food packing but as soon as it is scratched corrosion starts rapidly. This is one of the reasons why tin coating in food packing is more and more replaced by plastic coating.
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