Galvanizing is the coating of a metal with a more reactive metal to stop corrosion. Normally zinc is used to coat iron. The zinc coating corrodes instead of the iron, stopping the iron from corroding. Even if the zinc is scratched, it does not corrode. Metal corrodes after the paint is scratched. The zinc eventually corrodes all the way and then the iron starts corroding.
Galvanizing can happen in two ways. There is hot dip galvanising, where the object is dipped in a pool of liquid zinc. This makes a thicker coating that lasts a long time. It does not have a shiny clean surface, though, so some people would not like it as much.
There is also electro-galvanizing. This is the electroplating of zinc onto an object. It is shiny but thinner, so it does not last as long.