How to Acid Wash Concrete in 10 Steps

Concrete is a strong, durable material that holds up well to the elements. However, its drab, grey color doesn’t impress as much as other materials.

To prepare concrete for a more decorative layer, it has to go through a process called acid washing.

Steps to Acid Wash Concrete

Once the concrete has been set and you are ready to add the decorative layer to the surface, you will need to acid wash the concrete. This will open up the pores of the concrete and prepare it to receive the coating.

To acid wash the concrete, you’ll want to follow these steps:

  1. Clean the area: Use a brush or vacuum to remove any dirt and grease from the area to prevent it from reacting with the acid.
  2. Choose which acid you want to use: Phosphoric, muriatic, and sulfamic acid all have different applications, so choose the acid that makes the most sense for your expertise and location.
  3. Don safety gear: Goggles, rubber gloves, and rubber boots are all recommended when handling dangerous acids.
  4. Add the acid to water: By pouring the acid into the water, you prevent the acid from splashing up and causing damage to your body or the surroundings.
  5. Hose down the area: The area you want to clean should be wet before applying the acid.
  6. Apply the acid and scrub it in: Once the acid is applied to the concrete, a brush or mop will ensure that the acid is spread in an even layer across the concrete.
  7. Wait 10 minutes: You should see the mineral deposits of the concrete start to bubble up within this time, meaning you’ll have a clear sign of when to start your clean-up.
  8. Neutralize the acid: Once the acid has done its job, using a base like baking soda or garden lime will neutralize the acid and remove its dangerous and corrosive properties.
  9. Rinse and dry the area: Rinse the area with water several times to remove the acid from the concrete.
  10. Clean up leftover acid: Add the neutralizing agent to any leftover acid in your bucket and discard the solution safely.
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Many concrete contractors will have guidelines on how to safely dispose of the neutralized acid.

This mixture should not be dumped into the sewer system or poured down the sink, so ensure that you and your workers do not do this.

FAQs

Here are some of the common questions about acid washing concrete:

Can You Acid Wash Existing Concrete?

You can acid stain old concrete, which is a similar process to acid-washing fresh concrete.

When Should You Acid Wash Concrete?

Acid washing concrete should happen after the concrete has cured and become hardened.

Does Acid Dissolve Concrete?

Acid does not dissolve concrete that has cured. Instead, it pulls minerals out of the concrete that would interfere with coatings or decorative layers.

Summary

Acid washing concrete involves using a strong acid to pull minerals out of the concrete that would interfere with coatings. These coatings can then be applied, improving the look or feel of the concrete.