Acid Etching of Concrete to Prepare Concrete Surfaces

Acid etching is the process of applying an acid solution to a concrete surface, allowing the acid to react with and ‘etch’ the concrete.

Acid Etching of concrete is a method for commercial concrete surface preparation that will remove most surface deposits on concrete.

Shot blasting is another method to prepare concrete surfaces but requires special equipment and trained professionals, special concrete contractors. Acid etching is the best surface preparation method available for do it yourself homeowners.

The following guidelines are suggested to acid etch your concrete.

Concrete acid etching will not remove sealers or concrete surfaces. They must be removed mechanically through shotblasting, sandblasting, or scarifying. Sealers that soak deep into the concrete may not be removable at all.

Acid etching is used for surface preparation of home shops, garages, basements, and general concrete.
If the concrete is contaminated with oils or grease, you must clean the surface with an alkali detergent cleaner and commercial degreaser, or use detergent in combination with a steam cleaner.

Types of Acid Etching Products

HYDROCHLORIC ACID
Sold in 31% solutions. Dilute to 10%-15%. Use 1 gallon for every 40-50 square feet. A dangerous acid with VERY strong fumes, recommended for professional concrete contractors only.

SULFAMIC ACID
A white powder dissolved in hot water, less dangerous to work with than the other acids and the best choice for non professionals. Mix one pound of Sulfamic Acid with 1 gallon of hot water to treat 300 square feet of concrete.

PHOSPHORIC ACID
Produces less fumes and can be used around acid vulnerable metals such as carbon or galvanized steel. Use a solution of 20% – 40% Phosphoric Acid.

Concrete Etching Procedure

1. Degrease and seal contaminated concrete areas, sand, degloss, strip or remove all existing coatings. Well bonded existing coatings can remain in place.
2. Clean concrete floors with a detergent and rinse throughly.
3.  Make the floor damp using tap water and examine where the water beads up on the exposed concrete. After completing the surface preparation retest with more water. Do not coat the area until water does not bead up.
4. Apply the acid solution evenly using a sprinkling can or acid tolerant pump spray unit.
5.  Work the acid solution into the concrete with a stiff bristle broom or scrubber.
6.   Let the acid etching solution sit for 5 – 10 minutes.
7.   Vacuum to remove the excess acid on the etched concrete.
8.   Before the acid dries on the concrete surface, remove residue with water hose or high pressure water sprayer and vacuum the remains.
9.   Neutralize any acid residue on the etched concrete with a diluted Simple Green solution. Do not use diluted liquid bleach as bleach and acids can have a dangerous chemical reaction. Rinse the entire area throughly with water. Improperly neutralizing the acid will damage the entire process.
10.    Wash the surface with a mineral/acid salt remover. Salts on the concrete surface do not easily rinse and lead to adhesion problems as they absorb moisture becoming corrosive liquids and/or as crystals grow on the surface. Hidden salts can be removed with a salt remover product. If you apply this product, it must be rinsed off well as it dissolves the salts. Watch for salt contamination which can cause disbonding of your new surface.
11.  Let the concrete dry and again sweep clean of any dust, dirt, and particles from the acid etching process.
12.   Seal the coat with our Glaze Coat – one part acrylic for that shiny, dust free surface or coat the floor with a light gray water based epoxy coating/primer.