Oxalic Acid to Clean a Fiberglass Bathtub

About Oxalic Acid

• Oxalic acid effectively cleans surfaces and is found in many commercial cleaners and rust removers. You can also purchase oxalic acid in a pure powder form, but it must be diluted before you can use it safely on fiberglass. The acidic cleaner effectively removes rust, mineral deposits and tough stains from fiberglass bathtubs and has a bleaching effect.

Application

• Before you apply oxalic acid to the fiberglass bathtub, always read the label carefully. Oxalic acid must be diluted when you purchase it at full strength. Dilute one part of oxalic acid with 10 parts of water. Apply the solution to the fiberglass bathtub with a nonabrasive sponge and let it sit on the stain for five to 10 minutes. You can leave the oxalic acid on tough stains for up to one hour. After the cleaner sits on the stain for the desired time, rinse it off the fiberglass with clean water. Apply the oxalic acid to the bathtub again if the stain remains.

After Application

• After you clean the fiberglass bathtub with oxalic acid, the surface may appear dull. If you notice that the area appears dull due to the oxalic acid, restore the shine with an application of white automotive cream wax. Dry the bathtub with a towel to remove the excess moisture, then apply the wax to the fiberglass with a clean washcloth. When you apply the wax, buff it over the surface carefully to prevent streaks from forming.

Warning

• Never mix oxalic acid with any other cleaners because it can create toxic fumes. Never get oxalic acid on your skin or in your eyes. Wear gloves, a mask and goggles when working with oxalic acid to protect your health. Never use abrasive cleaners such as steel wool or scouring pads to clean fiberglass because they will scratch the surface. Avoid applying oxalic acid to bathtub fixtures that are not acid-resistant because it can ruin the finish. Remove the rust with trisodium phosphate instead.