Nothing looks older, dirtier and more contaminated than the appearance of rust. Also known as iron oxide, rust is generally found around areas with liquids and metals. It takes on a reddish-brown hue and deteriorates over time if left untreated. Adding heat to an area with liquids and metals will speed up corrosion and rusting of the metal. Rust can be a particular problem on outdoor garden taps that are exposed to the elements. Treat rust around water taps with lemon juice or white vinegar. If that does not work, oxalic acid should help.
Squeeze the juice from a lemon into a bowl or pour 125 ml (1/2 cup) of white vinegar into a bowl.
Soak your sponge, with the rough part face down, into the lemon juice or vinegar.
Forcefully scrub the rust around the water tap. If the rust does not come off, try again with a rougher sponge. If the rust still does not disappear, then you will need to use an oxalic acid rust remover.
Pour a small amount of oxalic acid into a bowl and soak your sponge in the solution.
Scrub forcefully and the rust stain should disappear.
Make sure you wear gloves, because oxalic acid is toxic on contact with the skin.