Acid Washing versus Concrete Grinding to Prepare your Floor

Acid Washing versus Concrete Grinding to Prepare your Floor

The Big Question: Acid Washing or Concrete Grinding...

Concrete Grinding: The Key to a Lasting Epoxy Floor

This is an age old debate: Should you grind or acid wash/etch your concrete floor before you apply an epoxy coating?

The acid wash companies tell you that using their products are satisfactory and the professional flooring applicators swear by concrete grinding. So we did a video to show you the results of both methods being done side by side at the same time. You be the judge.

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Video Overview

Hi, my name is Tim McGary from Epoxy Flooring Co. Today I wanted to show you the difference between grinding a floor and acid washing a floor in preparation to put down an epoxy coating.

One of the most common questions I get asked from people who are looking to do it themselves is, “is it really necessary to grind the floor?” and the best way to show that is just to grind a section and right next to it we’re going to acid wash a section just to see what the difference is.

I’ve borrowed a friend’s garage and before I get in and do the entire floor I thought I would just show this first section just to get to the bottom of this question and answer it once and for all. So stay tuned.

So okay, so welcome back. Thanks to the wonders of technology we have been about two hours since we first started and this is the end result. So I’m going to ask a rhetorical question and the question is this, if you were a piece of epoxy what would you rather stick to?

So you can just see if you remember in the start of the video this was the really really badly marked section of concrete and I deliberately ground this just to see what result we get compared to the acid wash.

As you can see it’s vastly different. Just got a great finish on it and I’ve got exposed clean concrete pretty much all the stains have gone. I only did one pass over it, I could get it even better if we had to but you can just imagine if you’re a chemical and you’re looking for a home to latch onto that one looks pretty good. Obviously, we’ll be fixing that crack.

But this is the acid wash. So I did two two applications of the acid and I had it at about a 4 to 1 ratio which means I had one litre of hydrochloric acid and 4 litres of water so it’s a pretty strong mix. It went on and this is the end result vastly different to the grind.

So what you could probably say, and the best thing I could say, about this finish here is – it’s clean. It’s taken away a lot of the dirt but in terms of a substrate for a coating to latch onto I think you probably agree if you are that coating you’d rather be sitting on that one than sitting on this one.

Something else I just want to point out here on the acid wash finish is you can see some marks here – these marks around here. Okay, now I want to show you, this is something you really have to watch out for if you do decide to acid wash, hydrochloric acid residue.

That’s one of the hassles with using acid washing. What that means is I need to wash it again to get rid of it and I might have to do it two or three times and I might have to scrub it in between because if I try and put a coating of any sort onto that it won’t latch and it will peel off in the months or years ahead.

So that just takes more time. So it means that if you’re doing it at home I personally allow three days if I’m going to acid wash something – to wash it off properly – rinse it; rinse it; rinse it; rinse it; and then let it dry out as opposed to grabbing a grinder from your local hire specialist the job gets done in you know a fraction of the time and you’re literally coating it the same day.

So this gives us the best mechanical bond and that means that the coating can literally mechanically join onto its substrate as to those two types of bonds we look for in epoxy world. So one is a mechanical bond and the second is a chemical bond.

So chemical bond means that we want the epoxy to chemically bind to the substrate or the floor. The best finish you’re ever going to get is if you can combine those two things give a chemical bond and a mechanical bond that just never lifts it’s going to stay there for your whole lifetime.

Over here we really are reliant on that chemical bond because we haven’t taken off a layer of concrete to give the epoxy something to bind to but this can work it just takes a lot more work and you’re just not guaranteed a result down the track.

But you know for the home handyman it is an option but if you’re pretty good with your hands what I’d recommend is get down to your local hire place find yourself a grinder and have a go at that as you’re going to get a much better result in much shorter time.

Alright, that’s all for today. We’ll see you on the next one.

Related FAQs

  • What is the difference between grinding and acid washing a concrete floor in preparation for an epoxy coating?

    Grinding a concrete floor involves mechanically removing a layer of the concrete surface to expose clean concrete, which provides an excellent substrate for an epoxy coating to adhere to.

    Acid washing, on the other hand, involves applying a strong mix of hydrochloric acid and water to the concrete surface to clean it.

    However, it doesn’t provide as good a substrate for the epoxy coating as grinding does.

  • Is it necessary to grind a concrete floor before applying an epoxy coating?

    While it’s not absolutely necessary to grind a concrete floor before applying an epoxy coating, grinding provides a superior substrate for the coating to adhere to.

    It exposes clean concrete, removes stains, and allows the epoxy to form a strong mechanical bond with the concrete.

  • What is the problem with acid washing a concrete floor?

    Acid washing a concrete floor can leave behind hydrochloric acid residue, which can prevent an epoxy coating from adhering properly to the concrete.

    This residue needs to be thoroughly washed off, which can require multiple washes and scrubs, and then the floor needs to be allowed to dry out, which can take several days.

  • What are the two types of bonds that epoxy forms with a concrete floor?

    Epoxy forms two types of bonds with a concrete floor: a mechanical bond and a chemical bond.

    The mechanical bond is formed when the epoxy adheres to the rough surface of the concrete created by grinding.

    The chemical bond is formed when the epoxy chemically binds to the concrete.

    The strongest and most durable finish is achieved when both types of bonds are formed.

  • What is the recommended method for a home handyman to prepare a concrete floor for an epoxy coating?

    If you’re comfortable using power tools, it’s recommended to rent a grinder from a local hire place and grind the concrete floor.

    This method provides a superior substrate for the epoxy coating to adhere to, takes less time than acid washing, and allows you to apply the coating the same day.

About the Author

Tim McGary

Tim McGary, a notable figure in the construction industry since the Y2K era, pioneered Same Day Epoxy Flooring Systems in Australia. His expertise extends to polished concrete and single-colour industrial floors. Celebrated as the Australian Installer of the Year from 2021 to 2023, he now excels in creating full fake seamless epoxy floors for both residential and commercial spaces. Renowned for having the most 5 Star Google reviews in his field, Epoxy Flooring Co. blend Tim’s extensive knowledge and skills, ensuring every project is completed with precision and on time.

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