Efflorescence is a crystalline deposit of excess salts that travel with moisture to the surface of concrete. It is whitish in appearance and is naturally occurring in all concrete. Water must be present to carry and move the salts to the surface, once the water evaporates a white hazy substance is left on the surface; this is efflorescence. The denser the concrete, the more difficult it is for salts to travel through the concrete. By sealing with a penetrating concrete sealer, concrete is hardened up to 45% and efflorescence is eliminated. Since humidity can affect efflorescence, it has been shown that it can be a seasonal problem with efflorescence being most common during rainy seasons. Common causes of efflorescence include the movement of groundwater; since hydrostatic pressure can force water and salts to move to the surface. Bricks are also common surfaces that have problems with efflorescence and the combination of a brick and a certain type of mortar may result in increased salt deposits.
Efflorescence must be removed before applying a penetrating sealer. To remove efflorescence before applying a sealer we first recommend scrubbing the surface with a wire brush and water. If that does not work we recommend acid removal. Acid removal includes using Hydro-Etch 1000 on the efflorescence. (Please note Hydro-Etch 1000 must be diluted before use. Read all label instructions before application and wear the proper safety gear when applying.) After etching, the concrete needs to be rinsed with water and neutralized with baking soda or household ammonia.