Efflorescence on surfaces such as concrete leave a white, hazy substance behind. The cloudy material contains minerals such as salt and lime that travel to the surface of concrete by water. The water evaporates, leaving the chalky substance behind. The efflorescence requires an acidic compound to dissolve the minerals and agitation to remove it completely from the concrete.
- Skill level:
- Moderately Easy
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Things you need
- Water hose
- 2 cups white vinegar
- Shop broom
- Baking soda
- Muriatic acid
- Wet/dry vac
Wet the concrete with a water hose, saturating the surface. New efflorescence stains remove easily using only water.
Mix white vinegar with 4 cups water in a bucket to remove older efflorescence stains. Pour 1/3 of the mixture over one 8-foot by 8-foot section of the concrete.
Scrub the concrete with a shop broom to loosen the efflorescence from the surface. Pour 1/3 of the mixture over another section of the concrete and continue scrubbing. Mix additional vinegar and water if needed to finish removing the efflorescence.
Sprinkle 1/2 cup baking soda over the first 8-foot by 8-foot section. Scrub the baking soda into the concrete with the shop broom. The baking soda neutralises the acid. Continue to the next section, repeating the procedure.
Spray the white haze, vinegar mixture and baking soda from the concrete with the water hose. Start at one end of the concrete and spray back and forth as you force the mixture from the surface. Remove all the acidic moisture from the concrete.
Dilute 1 part muriatic acid with 10 parts water in a bucket, if the vinegar mixture doesn't remove all the efflorescence. Wearing gloves, sponge the acid onto any stubborn stains left on the concrete. Scrub the concrete with the shop broom and neutralise with the baking soda. Spray the muriatic acid and baking soda from the concrete with the garden hose.
Remove any standing water from the concrete with a wet/dry vac.
Tips and warnings
- If muriatic acid does not clean the efflorescence stains, use EDTA or ethylenediamine tetraacetic acid which dissolves calcium salts. Use as directed and test EDTA in a hidden area first to ensure it does not damage the concrete.
- Wear long sleeves, trousers, gloves and eye protection when handling muriatic acid or EDTA, to avoid burns.
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