How to Remove Tannin Stains from Concrete

Tannin stains are characterized by their dark brown color, similar to chocolate, thus being unique and easily identifiable. Basically, the main cause of tannin stains is rot, or water spreading through hardwoods, which leach resin or tannin.

In fact, tannin can easily stain surfaces, including bare concrete, and can sometimes be hard to remove. However, there are different methods for their removal, and generally soot or smoke removal methods are usually also effective. In this article, we will explain different methods on how to remove tannin stains from concrete, which vary in their effectiveness depending on the toughness of the stain.

How to remove tannin stains from concrete: The best proven methods

Method #1: How to remove tannin stains from concrete using oxalic acid

This method involves the use of a mild acidic solution of oxalic acid for cleaning light and relatively new tannin stains from concrete surfaces.

Things you will need

• Safety gear.
• Oxalic acid.
• Water.
• Stiff bristle brush.

Notes

• Oxalic acid or Othanedioic acid.
  Appearance: Colorless crystalline compound.
  Availability: It is available at cleaning and chemical supply stores.
  Hazards: This product is toxic, irritant, and corrosive to flesh.

Procedure

1. Wear your protective gear.
2. Prepare a 2-2.5% oxalic acid solution by mixing 3 ounces (85 grams) of oxalic acid with 1 gallon (3.78 liters) of water.
3. Scrub the tannin stain with the solution using a stiff bristle brush.
4. Rinse thoroughly with clean water.

Explanation

This method is simple and straight forward. First, put on your safety gear. Then, mix the crystalline oxalic acid with water to produce a concentration of 2 to 2.5 percent. For example, 3 ounces of oxalic acid per gallon of water gives the desired concentration, but, you can scale the amounts according to the size of the tannin stain. Next, saturate the stain with the solution, and use a stiff bristle brush to scrub the surface. And finally, rinse and flush the surface with clean water. Usually, several attempts are necessary to completely remove the stain. However, if this method shows no improvement from the first attempt, or during testing on a small area, use stronger and more effective methods.

Method #2: How to remove tannin stains from concrete using bleach

In this method, bleach is the active compound which can break down moderately stubborn tannin stains.

Things you will need

• Safety gear.
• Chlorine bleach.
• Water.
• Stiff bristle brush.

Notes

• Chlorine bleach is a liquid that consists of sodium hypochlorite, water, and other chemicals.
  Appearance: Colorless or slightly yellowish.
  Availability: It is available at the supermarkets and cleaning supply stores.
  Hazards: This product is corrosive to flesh, and can react with other chemicals to produce a toxic gas.

Procedure

1. Put on your protective gear.
2. Prepare the chlorine bleach solution.
3. Apply bleach to the tannin stains and scrub vigorously using a bristle brush.
4. Rinse and flush with clean water.

Explanation

This method follows the same procedure as the one for the oxalic acid, but the solution is usually more effective.

Method #3: How to remove tannin stains from concrete using a bandage

This method involves the use of a bandage soaked up in bleach, which is highly effective for removing stubborn tannin stains from concrete.

Things you will need

• Safety gear.
• Chlorine bleach.
• Absorptive cloth.
• Water.
• Stiff bristle brush.

Notes

• Chlorine bleach is a liquid that consists of sodium hypochlorite, water, and other chemicals.
  Appearance: Colorless or slightly yellowish.
  Availability: It is available at the supermarkets and cleaning supply stores.
  Hazards: This product is corrosive to flesh, and can react with other chemicals to produce a toxic gas.

Procedure

1. Wear your safety gear.
2. Soak up a piece of absorptive cloth with chlorine bleach, and place on the tannin stains.
3. Allow to stand for 30 minutes.
4. Remove the bandage, and scrub the surface using a stiff bristle brush.
5. Repeat steps 3 and 4 until the stain completely disappears.
6. Rinse and flush with clean water.

Explanation

This method is powerful in removing old and tough tannin stains from concrete. After wearing your safety gear, apply a piece of cloth saturated with chlorine bleach to the stain. Then, after about half an hour, remove the bandage and scrub the stain with a bristle brush. However, if the stain persists, you can repeat the process. And finally, rinse and flush the surface thoroughly with clean water.

Yet another method for the removal of tannin stains from concrete

Alternatively, you can scrub the surface first with a 1:4 solution of glycerin to water using a stiff bristle brush. Then, apply one of the methods for the removal of soot from brick walls and concrete surfaces. In fact, the cleaning with glycerin solution first boosts the effectiveness of the method which follows, and accelerates the process.