How to remove rust stains from a fiberglass tub

how to remove rust stains from fiberglass tub

If rust stains on your fiberglass tub are old and set, it can be a challenge, but you can still remove them using the right techniques. Get rid of rust stains on fiberglass using salt and lemon, a baking soda paste, or a white vinegar and borax mixture with a little elbow grease.

These methods take some time but are highly effective. To help preserve your bathroom’s good and clean-looking condition, ensure you remove rust stains from the fiberglass tub quickly.

Removing rust stains using lemon and salt

Fiberglass tubs are lightweight and easy to install. But, as water moisture spreads, these tubs become vulnerable to rust stains. The good news is, you might already have the things needed for this at-home stain-removing method: lemon and salt.

Lemon and salt are useful in removing stains and have fantastic cleaning properties. They allow you to remove the stubborn rust stains that are invading your fiberglass tub.

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If part of your fiberglass tub has rust stains just grab some lemon and salt and follow these steps:

  1. Find a bottle of lemon juice or lemon and salt.
  2. Roll the lemon along your counter to release the juices and cut it in half.
  3. Squeeze the lemon juice into a bowl.
  4. Soak a clean cloth or sponge into the lemon juice and dab the stained area with it.
  5. After dabbing lemon juice on the stains, place a generous amount of salt on each stained area. Make sure that you cover all the stains with salt.
  6. Let the salt sit for three to four hours. It will effectively remove the stains on your fiberglass tub.
  7. After the said time, remove the remaining rust stains using a microfiber towel by gently scrubbing the stain residue.
  8. Rinse your fiberglass tab with plain water and let it dry.

Baking soda is also useful in removing rust stains from your fiberglass tub

Baking soda is a great active agent in removing stains of any kind. Aside from eliminating stubborn stains, it also acts as an excellent deodorizer, removing foul smells from any material. In this method, we’ll be using the classic baking soda method in removing rust stains from your fiberglass tub. It helps you remove the stains and eliminate the foul odor of rust stains.

Follow the procedure below for optimal results.

  1. Find baking soda and microfiber cloth, which you’ll use to remove the rust stains.
  2. Create a baking soda paste with one-part water to one-part baking soda. Consider the number of rust stains on your tub when determining the amount of paste you’ll need. Start with a little and make more if necessary.
  3. Spread the baking soda paste on the stained area. Make sure that you cover all the stains for faster results.
  4. Let the paste sit on your stained tub overnight. Make sure that you don’t interrupt the procedure. Don’t use your fiberglass tub for a while to get the best results.
  5. The next day, use the microfiber cloth to remove the baking soda paste from your fiberglass tub.
  6. Rinse off the baking soda paste residues, and your tub should be stain-free. But if there are still stains, you can repeat the process. And add some salt to your baking soda paste.

Vinegar and Borax is the best way to eliminate rust stains from fiberglass tubs

Vinegar and borax properties support each other when removing rust stains on your fiberglass tub. Despite their acidic nature, these materials don’t let your tub lose its shine, leaving your tub looking as good as new. They work by softening the deposited minerals from rust stains, while also protecting glass surfaces from being scratched.

Vinegar and borax are straightforward to use, so just follow these steps to get the best results.

  1. Make a paste by mixing equal parts borax and distilled white vinegar.
  2. Put the paste on the rust stains. Use a toothbrush to scrub the stained area.
  3. Let it sit for a few minutes. But, make sure that you don’t let it dry, becoming powdery in appearance. If this happens, spray some vinegar in the area.
  4. Rinse it with water. If there are still rust stains, spray some more vinegar and use the toothbrush to scrub it again.
  5. If you don’t have vinegar, you can use hydrogen peroxide as an alternative. You can also use an abrasive sponge to scrub away the stains.

Commonly asked questions about rust stains

What causes rust stains on the fiberglass tub?

Bacteria buildup causes the rust stains on your fiberglass tub. Bacteria has high-iron content that can produce yellow or brown stains. Water with high levels of brass and copper are also reasons for stains. If you don’t regularly clean and maintain your tub, it can accumulate stains over time.

Another cause of rust stains on fiberglass is if you leave wet metal, a can of shaving cream for example, on the surface. If the can starts to rust, it can spread to the rub. Try using the processes above to avoid staining your clean white tub.

Can elbow grease remove rust stains?

Yes, but it’s not the easiest method. It requires force and effort. Vigorous polishing and cleaning won’t hurt your fiberglass rub, but you’d be better off trying another method first, such as a baking soda and vinegar paste.

If you try one of the techniques we listed first and there’s still a little rust stain left, you can probably get rid of the rest of it with a little elbow grease. Just make sure that you have a lot of patience.

Will vinegar completely diminish the oxidation coming from the fiberglass?

Yes. Older fiberglass often looks rusty because of oxidation (a chemical reaction of iron, water and oxygen). You can replenish and bring back the fresh look of your fiberglass using vinegar. All you need to do is to mix water and white vinegar and apply it to your tub.

Follow the complete procedure above to remove the oxidation in your fiberglass tub completely.

The bottom line

Prevention is always better than allowing stains to ruin your fiberglass tub. But if somehow rust stains start forming in your tub, don’t worry as you can remove them with any of the methods mentioned above. You can use salt and lemon, baking soda paste, or vinegar and borax to ensure your fiberglass tub stays in top condition.

how to remove rust stains from fiberglass tub


Michael René, consultant, is the leading stain removal expert in Denmark. Read about him and the rest of the team here

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