To acid etch the concrete floor slab or to concrete grind, the concrete slab is The Big Bang question of the flooring industry. Both methods of concrete preparation have their supporters and not so many supporters.
Correct concrete preparation is the key to a long and happy life for your new epoxy floor. Correct preparation means that the concrete pores are open enough for the epoxy to bond with the concrete and right surface profiling has been achieved.
The number one reason for epoxy failure and a short and miserable life span, not to mention tons of wasted money, is insufficient concrete preparation.
We are definitely for concrete grinding as a preferred preparation method, but we will discuss both methods, to see which one you are ruling for.
For years acid etching or acid washing has been the preferred process of concrete preparation. It is the process of applying hydrochloric/muriatic or buffered phosphoric acid to the slab. Followed by cleaning and rinsing the concrete with water after the etching reaction has been completed.
Why wash it with water you may ask? Well, we weren't experts in chemistry at school, but in this case, water neutralizes the acid wash solution.
Put chemistry aside, the way acid wash works is by eating through and removing the top surface of the concrete, some even say achieving the same result as concrete grinding.
Let's face it, throwing some acid on the concrete floor, waiting for a while to do its magic, and then rinsing it off with water, sounds like a kid's play.
Well for a couple of reasons really. The main one is acid washing, which does not work as well as concrete grinding.
For a start, acid etching works by reacting with the free limestone in the concrete. If there is any oil, dirt, or grime on the concrete surface, the acid etching will simply not be enough.
If not washed and removed properly, the acid can clog the concrete pores by creating a wet concrete dust film. This on the other hand will interfere with the epoxy and its bondage to the concrete slab, leading to eventually the epoxy peeling off.
If the acid is left on the concrete for longer than necessary, it can over-expose the concrete pores. Over-etching the concrete floor, can lead to injecting water and moisture into the slab when washing off the acid. This will lead to moisture being trapped underneath the epoxy and ultimately shortening its lifespan.
Finally, acid washing, if not careful with can damage pavement, stones, and grass. In many places, there are regulations on how to handle and clean acid, so it does not affect the environment.
To conclude, acid etching can be very unpredictable and unreliable, even when done by a professional. Many epoxy manufactures do not recommend using acid etching as a concrete preparation method.
Now let's talk about the bad boys of the flooring preparation.
Yes, you guessed it right! It's the concrete grinders.
Concrete grinders use different attachments to grind and level the concrete. These diamond attachments remove all dirt, oil, grime, the grainy compound on the surface (acid cannot remove it), to create a clean and smooth surface.
As every concrete is different in terms of texture, composition, hardness, alternating between different grinding heads, helps achieve the surface needed.
When starting the grinding process, the flooring expert will start with a low grit of 30, moving up to 60/80 grit, until the concrete is ready for the epoxy application.
In between each grinding, the concrete is vacuumed, to ensure there is no dust laying around.
Overall, concrete grinding provides more precision and control over the surface and the professional preparing your floor can get the exact texture they need.
We say this a lot, but concrete texture can be the difference between a happy decades-old epoxy and a sad peeling off after one year of epoxy.
If you decide to do your floor, by using a DIY kit, we beg you not to use acid washing. We simply want to save you money.
If you are confident with your capabilities, you should rent proper grinding equipment, suitable for the job.
Bear in mind you will need to think about how to know you have the right texture and how you will control the concrete dust flying around.
If you are going to hire a contractor to install your new epoxy floor, make sure they diamond grind the concrete.
An epoxy flooring contractor that acid etches the concrete may be cutting corners to cut expenses and will most likely not offer a high-quality floor finish.