How to Remove Rust Stains From Concrete With a Pressure Washer

Rust stains on a concrete surface are hideous. They are as unsightly as they’re stubborn to remove. Most people fail to realize that you can’t simply pressure wash a rust stain from a concrete surface.

To remove rust stains from concrete with a pressure washer, you first need to treat the surface with a concrete rust remover. Unlike other stains, rust penetrates the surface of the concrete, making it difficult to remove. Rinsing off the rust remover with a pressure washer ensures great results.

If you have unsuccessfully tried to pressure wash a rust stain from a concrete surface without success, chances are you’re doing it wrong. Read on for the best way to remove rust stains from a concrete surface with a pressure washer.

Pressure Washing Rust From Concrete

Your choice of a rust remover depends on the duration of the stain on the concrete surface. The longer the stain sits on a concrete surface, the more challenging it is to remove.

Therefore, we’ll break this tutorial into two categories to address both minor and major rust stains.

If you’re unsure how old the rust stain is, it’s advisable to start with the minor rust stain treatment. If that doesn’t work, you can then progress to the major rust stain treatment.

Removing Minor Rust Stains From Concrete With a Power Washer

You need to be sure of the type of concrete surface you’re dealing with before you can commence with the rust treatment. Painted and acid-treated concrete surfaces are a tad delicate and are susceptible to acidic cleaning products.

For painted and other delicate concrete surfaces, it’s best to dilute the cleaning solution. Be sure to use a one-part cleaning solution to one-part water ratio for these surfaces.

To remove minor rust stains from concrete, you’ll need:

  • Liquid detergent
  • Plenty of water
  • Pure lemon juice or vinegar
  • Rubber gloves
  • Safety glasses
  • A pressure washer

Follow this procedure:

  1. Clean the rust-stained concrete surface with soap and water. The key here is to strip away the dirt or grease on the concrete surface. A thick layer of dirt and grime keeps the acids from effectively penetrating the concrete surface and removing the rust stain.
  2. Rinse off the soapy solution from your rust-stained concrete surface with plenty of clean water. Be sure to remove all traces of the soap from the concrete surface.
  3. Apply the undiluted lemon juice generously over the rust-stained area. In its pure form, lemon juice is a powerful acid with excellent stain removal capability.
  4. Soak the entire rust-stained concrete surface with pure lemon juice and let it sit for 10 to 15 minutes. Letting the acid lemon juice steep for 15 minutes allow it sufficient time to penetrate the surface and react with the rust stain.
  5. Rinse the acid from the concrete with a pressure washer. A pressure washer is an excellent alternative to scrubbing the surface with a brush. Be sure to choose the right pressure washer nozzle. You need a 0 or a 15-degree nozzle for this job to deliver a strong and forceful spray. The lower the degree of a pressure washer nozzle, the more pointed and forceful the spray.
  6. Rinse the rust-stained area and leave it to dry. If the stain persists, have another go at it following the same process.
  7. If the second run doesn’t clean away the rust stain, substitute the lemon juice with white vinegar. Vinegar is an excellent cleaning solution and stronger than lemon juice. Follow the same cleaning process with the white vinegar.

Removing Major Rust Stains From Concrete With a Pressure Washer

If the white vinegar and lemon juice method fails, you’re dealing with a major rust stain on concrete. It’s time to upgrade to a commercial rust cleaner or a stronger acid.

The best concrete rust stain removers have oxalic acid as the active ingredient. Other useful acids include hydrochloric acid and trisodium phosphate, which is diluted with water.

Avoid leaving hydrochloric acid on a concrete surface for too long, as it can lead to discoloration. If you plan on leaving the acidic solution to steep a while, dilute two parts acid with one part water to keep it from turning the concrete surface blue.

Since acids are corrosive liquids, you should follow all precautions on the bottle’s label and wear protective gear.

To remove a significant rust stain from concrete, you’ll need:

  • A commercial rust remover
  • Soap
  • Plenty of water
  • Safety glasses
  • Rubber gloves
  • Long-sleeved shirts and long pants
  • A pressure washer

Follow this procedure:

  1. Put on the protective gear and gather all the material and equipment.
  2. Clean the rust-stained concrete surface with soap and water. It helps to strip away the grime and grease from the concrete surface. Dirt can mar your results by limiting the acid’s ability to penetrate beyond the concrete surface.
  3. Rinse the rust-stained area with plenty of water and leave it to dry. Applying the commercial rust cleaner on a wet surface might lower its efficacy. Be sure to check the instructions on the label for more details.
  4. Apply the rust remover or the acid generously on the rust-stained concrete areas. Follow the directions and safety instructions on the bottle.
  5. Let the acid or the concrete rust remover sit for the recommended duration. Resist any attempt to let the mixture sit longer as it might ruin the concrete surface.
  6. Rinse with the pressure washer once the recommended steeping time lapses. Since a pressure washer has 80x the pressure of a hose pipe, it’s more effective than a scrubbing brush. A pressure washer is recommended when dealing with stubborn rust stains on concrete surfaces.

Conclusion

It’s not enough to pressure wash a rust stain from a concrete surface. Rust stains penetrate deep into the concrete’s porous surface. You need to apply a concrete stain remover for the best results and then rinse it off with a pressure washer. Undiluted lemon juice or white vinegar are the ideal options when dealing with minor rust stains on concrete.

For stubborn concrete rust stains, you’re better off with a commercial concrete rust stain remover. Such removers contain oxalic acid as an active ingredient. Hydrochloric acid and trisodium phosphate make excellent substitutes.

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