Preventing corrosion: Prevent Rusting, Physical Barriers, Electrotrapping & Sacrificial Protection

PREVENT RUSTING: - oxygen can be excluded by storing the metal in an atmosphere of unreactive nitrogen or argon - desiccant: a substance that absorbs water vapour, so it keeps the metal dry PHYSICAL BARRIERS: - painting - oiling and greasing - coating with plastic ELECTROTRAPPING, using electrolysis to put a thin layer of a metal on the object: - the cathode is the iron or steel object - the anode is the plating metal - the electrolyte contains ions of the plating metal SACRIFICIAL PROTECTION: - If a metal is in contact with more reactive metal (The more reactive metal oxidises more readily than , so it ‘sacrifices’ itself while so the less reactive metal does not rust. Once the sacrificial metal has corroded away, it can simply be replaced) GALVANISING: When iron is coated in zinc, the process is called galvanisation. The zinc layer stops oxygen and water reaching the iron. Zinc is more reactive than iron, so it also acts as a sacrificial metal. This protection works, even if the zinc layer is scratched