“Do I have to etch new concrete for a garage floor coating?” This is one of the more common questions that we get from those who want to apply epoxy or a DIY garage floor coating kit. If you are not that familiar with concrete coatings, then we can understand why this question would come up after reading the application instructions.
The short answer is: Yes, even new concrete needs to be etched before applying epoxy or a similar type of garage floor coating.
Etching is part of the concrete preparation process. And what many people are not aware, is that proper preparation of the concrete before a coating is applied is the most important part. In fact, poor concrete prep is the leading cause to epoxy floor coating failure.
Also known as concrete surface profiling, the process of acid etching opens the pores of the concrete and creates a rougher surface. This is needed due to the viscous nature of epoxy and other coatings. They are very thick in consistency – much thicker than paint for example.
This thickness does not allow epoxy to penetrate into the surface of concrete very well, nor does it allow it to create a strong mechanical bond. When the pores of concrete are opened up and the surface is made rougher, epoxy and other garage floor coatings will penetrate into the concrete and create a tenacious bond with the surface as it cures.
New concrete can restrict penetration of epoxy even more than older concrete does. The reason for this is that the surface has been freshly troweled smooth, providing even less mechanical grip and access to the pores at the surface.
Concrete surface profiles are often referred to in the industry as CSP. A number assigned to the CSP dictates the actual profile or roughness of the surface. You can see magnified examples of CSP profiles in the chart below.
The majority of garage floor coatings require a minimum surface profile of CSP-1. This can usually be achieved by etching the concrete. Some of the thicker industrial coatings may require a minimum CSP-2 profile. This can only be achieved through grinding of the concrete.
Is grinding better than etching? Grinding will always create a rougher and more desirable profile. However, many garage floor coatings and DIY epoxy kits can do well with etching only if it is done properly.
Cleaning the concrete surface of dirt, oil, and other contaminants before etching is important as well. Oil in particular will not allow epoxy or other garage floor coatings to penetrate into the concrete. In addition, acid etching will not remove oil.
If you attempt to apply a coating over an oil stain that was not cleaned properly, the oil will actually repel the coating and form what is known as fish eyes. These are crater-like openings in the coating that begin to form after the coating has been applied.
Important to note is that you need to match the strength of the concrete etching product you use with what the manufacturer or vendor recommends. Not all concrete etching solutions are created equal.
For example, the less expensive DIY garage floor coating kits that you can purchase from your local home improvement center typically come with a citric-based concrete etch. Also known as a “Clean & Etch”, these are Eco friendly and safe for the environment.
Nevertheless, this particular type of citric acid etch is also the least effective at etching concrete for coatings. They tend to work well enough in most circumstances for these epoxy kits since most are low in solids content (not as thick) and do not require as rough a surface profile. However, you would not use this type of product for a higher quality coating.
Acid etching is the best for providing a true CSP-1 surface profile of your concrete. However, muriatic acid is not Eco friendly and requires taking the proper steps to be safe and successful.
If acid etching is not for you, there are safer etching alternatives that are stronger than what you can find at your local home improvement center.
Are there garage floor coatings that don’t require etching?
When people discover that etching of the concrete is required for a garage floor coating, it is sometimes followed up with the question, “What coating can I use on my garage floor that doesn’t need etching?”
The answer is almost none. However, Rust Bullet is one manufacturer that makes a garage floor coating that you can apply without having to acid etch.
Their decorative option is called DuraGrade Concrete, while the more industrial looking version is Rust Bullet for Concrete.
Before you get too excited though, pay close attention to the water absorption requirements that the concrete needs to pass before Rust Bullet can be applied. If the concrete is too smooth or does not absorb water very well, then you will still be required to etch the concrete.
Before Rust Bullet introduced itself a few years back, there were no traditional garage floor coatings to speak of that did not require etching or grinding of the concrete. And to our knowledge, there have not been any others to choose from since.
The simple fact of the matter is that the manufacturers of concrete coatings know that there is not a substitute for proper concrete prep. If you don’t want issues with peeling and you want to take advantage of the many benefits of a quality garage floor coating, then there is no getting around the fact that you will need to etch your concrete at a minimum before applying epoxy or a similar coating to your garage floor.
What CSP can I expect to obtain with Rust-oleums Clean and Etch. Main ingredient appears to be Urea Monohydrochloride which best I can tell is an organic acid salt.
Hi Peter. From our experience Rust-Oleum Clean and Etch will not achieve a CSP-1 profile in most cases. However, it tends to rough up the profile and open the pores enough to work OK for the Rust-Oleum products since they are lower in solids content and less viscous than higher performance coatings.