Use a wire brush, either hand operated or on an electric drill, on the surface and try to remove as much rusty material as possible, don’t be worried if you create a hole, attack the surface with a vengance.

Anything that is vaguely rotten will come off, sometimes if the rust is severe, you may need to use an angle grinder with a grinding disk. Grind the surface lightly. Brown dusty powder is rust and must come off, only when you start making sparks and the surface is shiny can you move on to another area.

Once all rust has been removed you can patch up the holes as needed (See next section)

You must then clean the surface with water and let it dry properly.

If the surface is vaguely rusty or still brownish/blackish in colour you must paint it with a Polycell product called RUSSIST. An alternative is straight phosphoric acid but it is less effective than RUSSIST.

Russist contains phosphoric acid which reacts with the rust (iron oxide) and forms iron sulphate which is dark blue/black in colour and is resistant to further rust. It is for this reason that you must only apply this product to RUSTY metal as it does not bond on clean steel.

You should apply the russist as instructed on the container, then apply your favourite paint as the russist acts as a primer for most paints. Russist can be sprayed on and you can apply spray paint onto russist.

If you used straight phosphoric acid (With gloves !) you must thoroughly wash the item after the it has stood for a good few hours, then let it dry and apply paint.