Most food is stored on the supermarket shelves in tin coated iron containers. Tin is not a very reactive metal and will not rust in the presence of oxygen. The iron is totally covered with tin in order to protect it from rusting. If the tin is scratched and the iron exposed the iron rusts very quickly. Explain why?
Zinc coated iron will not rust if scratched. Explain why?
Why is galvanised steel not used for food containers even though it prevents iron from rusting?

Aluminium is a very reactive metal. It reacts with water to produce hydrogen gas in a similar way to sodium. The reason why we can make cooking pots out of aluminium is the fact that aluminium oxide (aluminium rust) forms an impenetrable layer. Unlike iron rust, that flakes off to expose more iron, aluminium rust forms abarrier protecting the aluminium from the oxygen. Salt water tends to break apart the aluminium rust layer.

A sea side holiday house was built very close to the ocean. Explain why an aluminium window frame secured to the wood with iron nails fell off the support.