When considering how to remove rust from tiles, first take into account the type of tile. For non-porous tiles (glazed ceramic tiles), apply lemon juice to the rust stain and cover with coarse salt. Leave on for a few minutes for a small stain, or up to 1 hour for stubborn stains. Then, using a sponge, rub the area gently.
Alternatively, you can create a paste by mixing baking soda and lemon together and apply to the area. Then, remove as above.