Galvanised iron pipes have a coating of Zinc . Galvanization is a method used for coating metal to protect it against corrosion. The most common method is hot-dip galvanizing , in which steel sections are submerged in a bath of molten zinc. How galvanizing protects from rusting: It forms a barrier that prevents corrosive substances to come in contact with oxygen and water. The zinc serves as a sacrificial anode so that even if the coating is scratched, the exposed steel will still be protected by the remaining zinc. The zinc surface reacts with the atmosphere to form a compact, adherent patina that is insoluble in rainwater.