High iron in the water causes rust stains all over the house: toilets, sinks and bathtubs especially. Iron stains are a little difficult because they are tightly bonded at the molecular level. This tight bond wraps around the material and holds on. When these stains attach to the shower curtain, regular soap and water will not help. Using a few regular household items in the right sequence can break this tight bond and allow the curtain to be cleaned as usual.
Spray a light layer of lemon juice onto the shower curtain. This causes the pores to open up and makes them more susceptible to other cleaners.
Douse the area with white vinegar. The white vinegar acts as a cleaning agent when it gets deep into the pores of the shower curtain.
Apply a generous amount of salt to the stained area. The salt will soak up the iron deposits and will act as a safe abrasive to clean the shower curtain.
Take a soft scrub brush and brush the stain until the iron stain is removed. Rinse the shower curtain with hot soapy water. If the stain does not totally come up then repeat the process.
Hang the shower in the sun to dry. If this is not a possibility then hang it back on its hooks in the shower. The better the ventilation the quicker the shower curtain will dry.