Acrylic tubs are less expensive than many forms of tubs. They are also one of the most widely used forms. However, this material is more delicate than tubs made of stronger materials. Rust stains can cause a lot of damage to the tub if treated improperly. However, with appropriate cleaning products and techniques it is possible to successfully clean away all rust stains without causing permanent damage to the tub itself.
Bleach causes the finish on an acrylic tub to disintegrate and can permanently damage or even ruin the tub. It is important to never use bleach products on acrylic tubs. The best products to use on the rust stains are rust-fighting products that are meant to be used on a variety of surfaces. Most calcium and rust remover products will work well on acrylic surfaces. Lemon juice will also work for minor rust stains, but will not work on the toughest stains. As a last resort an abrasive powdered cleaner can be used to help scrub away the stain.
First, get some lemon juice, salt, rust cleaner, powdered abrasive cleaner, soft brush, soft cloth and a bucket of warm water. Apply the simplest methods of cleaning first. Use the lemon juice mixed with a small amount of salt. Let it sit in the rust stain for several minutes, then wipe away with a damp cloth. In all likelihood this will not be effective enough. Next use the rust cleaner, making sure it is safe to use on acrylic. Follow the package directions. Sometimes the cleaner needs to sit for awhile, and sometimes it should be wiped away immediately. Only if this measure does not work then move on to the abrasive powders.
A pumice stone can be used to remove stains that are deeply ground into the acrylic tub, but usually the introduction of such harsh materials will cause the tub to be damaged. Abrasive powders are usually gentle enough to use on acrylic tubs although they can sometimes ruin the finish. A circular motion is usually the best for wiping or rubbing away any rust stains. Always wear rubber gloves when working with chemicals of any kind and work in a well-ventilated area.