Because your pool deck is constantly wet, rust stains can develop. This can be avoided by not placing metal objects around your swimming pool or, if you do, by painting a thin layer of clear sealant on the bottom of metal pots or poles. When you discover rust on your pool deck, clean it as soon as possible to prevent it from getting worse and becoming more difficult to remove.
Soak a clean cloth in distilled white vinegar.
Lay the cloth over the rust stains on your pool deck.
Let the cloth sit there for several hours or until it has dried completely.
Remove the cloth and scrub the surface with a pool brush.
Dip the pool brush in distilled white vinegar and continue brushing if the rust stains do not come off easily.
Repeat the process again if the rust stains are still visible.
Rinse the area with clear water and let it air dry completely.