corrosion

• corrosion is when metals react with substances in their environment and are gradually destroyed
• iron rusts. in order to rust, it needs to be in contact with water and oxygen.
• iron + oxygen + water -> hydrated iron (III) oxide
• corrosion only happens on the surface of a material exposed to air.
• aluminium aren't completely destroyed during corrosion because aluminium oxide that forms when aluminium corrodes doesn't flake away. forms a nice protective layer and stop any further reactions
• barriers - painting. Coating with plastics. electroplating - using electrolysis to reduce metal ions onto the iron electrode. oiling/greasing
• sacrificial method- placing a more reactive metal such as zinc or magnesium with the iron, water and oxygen then react with this instead of iron
• galvanised - spraying a coating of zinc. the zinc layer is firstly protected, bit if scratched, the zinc around the site of the scratch works as a sacrificial metal