Although iron is next to tin in the reactivity series, the oxide coating that develops on iron is porous, which is why iron rusts. The low melting point of tin also means that it is easy to run sheet steel through a bath of tin without any fear that the steel might melt. The disadvantage of using tin plate Tin is plated onto iron or steel to protect it from corrosion, but it is only good if it remains unscratched. This is an important reason why aluminium containers have replaced tin-plated ones in recent years. Metals can be placed in order of how vigorously they react in a list called a reactivity series.
Tin is below iron in the reactivity series.
Therefore exposed iron will always corrode when placed in a damp environment with tin. This is why steel cans rust badly as soon as they become scratched. If a nail with a small tin collar is placed in water. This shows that tin speeds up the corrosion of steel and shows why tin-plated objects are only protected provided the tin remains unscratched.