How to remove rust stains from fiberglass tub

Rust stains in a fiberglass tub can be unsightly and difficult to remove. Over time, iron and other minerals in water can cause orange and brown rust stains that build up on the surface of your tub. While scrubbing with bathroom cleaners may help lighten these stains, getting rid of rust in a fiberglass tub completely often requires extra work.

The porous nature of fiberglass means rust has a way of settling in and becoming stubborn. However, don’t lose hope! With the right tools and techniques, you can banish those stubborn rust stains from your bathtub. This article provides a step-by-step guide to removing rust stains from fiberglass tubs using common household ingredients.

remove rust stains from fiberglass tub

Assess the Stains

Before doing anything, inspect the tub closely and identify where the rust stains are located and how concentrated they are. Light colored stains will likely come out easier than darker, concentrated spots. Make note of the heavily stained areas that will require extra attention. This will help you figure out the best approach.

For example, you may need to focus on using a rust remover paste on the intense stains first before moving onto gentler cleaning methods for the overall surface. Gather the supplies you’ll need based on how challenging the stains appear.

Here are some examples of light, medium, and heavy rust staining:

  • Light: Soft orange staining in small spots across tub surface
  • Medium: More concentrated brown staining along drain or bottom of tub
  • Heavy: Dark or black rust spots deep in the fiberglass

Gather the Right Supplies

Removing set-in rust stains requires using the right tools and products. Here’s what you’ll need to get started:

  • Protective gear like rubber gloves, safety goggles, an apron or old clothes
  • Mild abrasive cleaner or scrubbing powder (like Soft Scrub or Bon Ami)
  • Rust removal spray (ex. Whink Rust Stain Remover)
  • White vinegar
  • Lemon juice
  • Baking soda
  • Old toothbrushes and scrub sponges
  • Small brushes for concentrated stains
  • Plastic scraper or putty knife
  • Dry cloths and microfiber towel
  • Tub sealant (ex. Wet & Forget Shower Sealant)

Make sure you have all these supplies assembled before tackling the rust stains. This will make the process faster and more efficient.

Recommended Supplies:

Whink Rust Stain Remover Spray$8
Soft Scrub All Purpose Cleanser$3
Dr. Beckmann’s GK Rust Stain Remover$8
Wet & Forget Shower Sealant$20
Concrobium Mold Control Spray$10

Prep the Tub

Before doing any type of scrubbing or cleaning, it’s important to dry the tub first. Leftover moisture can dilute cleaners and make them less effective at removing the rust stains. Wipe down the tub thoroughly using old rags or paper towels. Make sure to get into the corners and around the drain.

Once dry, do a test spot of your cleaner or stain remover in an inconspicuous place like under the lip or along the side. Check to make sure it doesn’t damage or discolor the surface further. You don’t want to exacerbate the problem.

Apply Rust Stain Remover

For concentrated rust stains, start by applying a commercial rust remover spray. Whink Rust Stain Remover and CLR Calcium, Lime and Rust Remover are two popular options. Spray the product directly onto the intense rust stains. Let it sit for 5-10 minutes before scrubbing. The acidity in the cleaner will help break down the rust.

You can also mix lemon juice and baking soda to make a DIY rust stain remover paste:

  • Combine equal parts lemon juice and baking soda
  • Spread paste onto severe rust spots
  • Let bubble on stains for 2-3 minutes
  • Scrub with brush

The citric acid in lemon juice dissolves rust stains. The baking soda boosts the effect.

Scrub the Stains

Now comes the elbow grease! Take an old toothbrush, small scrub brush, or plastic scraper and start gently scrubbing the rust-stained areas. Apply light pressure and work in circular motions. Let the cleaner or stain remover do most of the work.

For larger areas with lighter stains, use a mildly abrasive cleaner like Soft Scrub combined with a sponge or scrubbing pad. The micro-grit in the cleaner will help lift stains when scrubbed. Always check to make sure the cleanser isn’t scratching or damaging the tub surface.

Rinse Thoroughly

Once you’ve focused on the heavy rust spots, rinse the tub several times with warm water to remove all residue. Wipe the surface down to remove any leftover cleaner or loose rust particles. Inspect to see if the stains have lightened or come off completely. If not, you may need to do another round of stain remover and scrubbing.

Whitening with Vinegar

For an all-over brightening treatment, make a solution of one part white vinegar to two parts warm water. Fill a spray bottle with this mixture. Spray it generously over the bottom of the tub and let it sit for about 10 minutes. The acidic vinegar will help dissolve any lingering rust stains.

After 10 minutes, scrub the tub all over with a sponge. Rinse thoroughly with warm water. Vinegar is a safe yet effective way to get rid of orange discoloration from rust stains in a fiberglass tub. For extra whitening power, sprinkle some baking soda directly onto the damp surface before scrubbing.

Inspect and Repeat

Once the tub is scrubbed and rinsed, go over it once more with a clean, dry microfiber towel. Make sure to buff into crevices and corners. Take a close look at the areas that had rust stains. Check if the stains are completely removed or if you might need to do spot treatments with a brush and rust remover again. A thorough inspection now can prevent the stains from coming back quickly.

For stubborn spots, repeat the stain remover, scrubbing, and vinegar rinse steps until the stains disappear. This may take several treatments over days or weeks for difficult rust stains.

Seal and Protect

As a final step to prevent future rust stains, apply a sealant and protector made for fiberglass tubs. Protecting the porous surface will keep iron, minerals and other metals from setting into the tub and causing discoloration.

Apply the sealant carefully according to directions, let dry completely, and do a final wipe down. Re-apply every 1-2 months for ongoing protection.


While dealing with rust in a fiberglass tub can be a challenge, having the right game plan and supplies makes removing the stains much easier. With the techniques outlined here, you can banish rust stains safely without damaging the tub surface.

Just remember to:

  • Assess stains and gather supplies
  • Prep the tub properly
  • Use rust-fighting cleaners
  • Scrub thoroughly
  • Whiten with vinegar
  • Seal the surface

Soon you’ll be able to enjoy a sparkling clean, stain-free bathtub once again.

Sharing Is Caring:

As the founder of Clean It Spotless, I am Melissa Walker, a leading expert in removing tough stains from fabrics, carpets, and upholstery. With over 10 years of experience in the cleaning industry, I have developed my own natural, non-toxic stain-fighting formulas that lift stains while preserving the integrity of the underlying material. My stain removal tutorials are widely read online, and I have appeared on local TV segments demonstrating my techniques. I also present popular stain removal workshops at community centers and schools.

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