Best Method of Concrete Preparation

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Epoxy paints don’t adhere to all things. Fortunately, they strongly adhere to properly prepared concrete. So much so that epoxy coatings are one of the most durable flooring applications available. But proper concrete prep requires that several assessments be made before epoxy application even begins. Determining the best method of concrete preparation, acid-etching versus diamond grinding, is one of these assessments.

Concrete Preparation Assessments

In a prior blog, I discussed the importance of assessing concrete moisture (Moisture Mitigation). Assessing moisture with a moisture meter is critical because it determines which epoxy type should be applied to your concrete floor. A high moisture reading would require the application of a moisture-mitigating epoxy coat as primer.

But there is a second important assessment. It involves testing the concrete to determine the viable methods of creating a concrete “profile”. (For a prior blog on concrete profiles, read Proper Concrete Preparation). Do you need to use a commercial diamond grinder or is acid-etching a viable method? Although professional installers rarely use acid-etching, it’s the “go-to” method for hardware store DIY epoxy kits.

But depending upon the state of the concrete, acid-etching may be a non-starter. A simple test will determine if the concrete you intend to coat has a curing agent only, a sealer, or a pigmented coating. If either of the latter two coatings is present, acid-etching will not be sufficient to produce the required concrete “profile” and the epoxy paint will not adhere. In these cases, only diamond grinding will suffice.

Preparing the Test Solution

The test solution used in this assessment is made up of water and muriatic acid. Muriatic acid is another name for hydrochloric acid (HCl), a very strong and corrosive chemical. Although this test solution is often included as part of DIY epoxy kits, you can prepare one yourself by simply adding 4 parts water to 1 part (31.45%) muriatic acid.

Performing the Test

It is the way in which the concrete reacts with this test solution that determines what coating is present, if any. To start, simply add several drops of the prepared test solution to the concrete and closely watch for a reaction.

Use the table below to determine what coating type is present:

Coating Type

Properties of Existing Concrete

Color of Concrete

Reaction w/ Muriatic Acid

Curing Agent Only

Gray Concrete is Visible Reaction (“Bubbling”)

Clear Sealer

Gray Concrete is Visible

No Reaction

Pigmented Coating Pigmented (Concrete Not Visible)

No Reaction

If the concrete is gray and the solution reacts to cause bubbling, your concrete incorporates a curing agent only (that is, no coating is present). However, if there is no “bubbling”, the floor has an existing coating, either a clear sealer or pigmented epoxy.

All Things Considered?

If the test determines that only a curing agent is present, acid-etching is a viable method of concrete preparation. However, if a clear sealer or pigmented epoxy is present, only diamond grinding will produce an acceptable profile.

But even if the test suggests the viability of acid-etching, there are still other things to consider. Most importantly, acid-etching is only acceptable for well-ventilated areas like patios or garages. Due to acidic fumes, this method cannot take place indoors; only diamond-grinding with the proper dust-reduction attachments is an option. Furthermore, diamond-grinding (or bead blasting) is suggested to provide a more effective profile for larger commercial spaces, in lieu of acid-etching, even if no coating is present.

The Wrap

You can see how acid-etching, the “go-to” method for hardware store DIY epoxy kits, is so limiting. Acid-etching as a means of preparing concrete may be a viable solution, but it is imperative that you assess for the presence of existing coatings first. Etching previously coated concrete will be a waste of your time and money.

If you want an epoxy floor installed that will last for years, call a professional contractor. Don’t hire an inexperienced contractor or attempt a DIY…both will be costly over the long run. Visit us at to learn whether our floor coatings are the right choice for your space.



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