Preventing Corrosion

• Metals corrode when they react with oxygen and water in the environment
• When iron objects or or objects containing iron corrode , the term rusting is used
• Iron + Water + Oxygen ---> hydrated iron (III) oxide
• How can painting , electroplating or greasing a metal object prevent corrosion?

  It stops oxygen and water from reaching the surface - however if the coating is damaged , the metal will start to corrode
• How does sacrificial protection prevent corrosion?

  A more reactive metal is placed in contact with the metal . For example - Blocks of the more reactive magnesium metal are attached to an iron or steel object . As magnesium is more reactive than iron , it reacts and loses electrons instead of the iron
• How can galvanising be used to protect and prevent the corrosion of iron and steel objects?

  The object is coated in a layer of zinc - the zinc layer stops oxygen and water from reaching the metal and stops corrosion - If the surface of the zinc is scratched , it does not matter as the zinc provides sacrificial protection
• In sacrificial protection the more reactive metal reacts and loses its electrons instead of the iron or steel object that it is protecting
• What do aluminium objects have that protects them from corrosion?

  A thin layer of aluminium oxide , which acts as a barrier and prevents the aluminium from reacting further