Etching vs. Grinding

[tomsop]

I watched a This Old House youtube video that covered how to epoxy a garage floor and they prepped the floor with acid etching. Another popular set of videos by the Idaho Painter says that his 15 years of experience with epoxy involves a process that relies on acid etching but he mentions sanding is another method and then he goes on to just use acid etching only in his demo video series. And then we have this forum where many people use a grinder from Home Depot to prep their floor. Then I read people take many hours (some take 12 hours) to grind away on their garage floor. I have put off doing this because I am not sure what is the most efficient and effective use of my time and costs involved. I think acid etching looks relatively painless vs. 12 hours riding a grinder all over a 400 sq foot garage yet don't want to spend 700 dollars on materials to learn I should have grinded vs. I could have saved 11 hours with just pouring some acid on the floor.

I know there is a good number of people on here who recommend grinding - are there others who got a good result from just acid etching instead?

 

[krouchchocolate]

I'm in the same dilemma, but I know that if I was going to spend $600 on epoxy, then I will grind the floor like what is recommended on here.

 

[bdamico]

Many, many people have fine success with etching but the people who know what they are doing--(1) pros who do installs and (2) manufacturers--are rarely gonna tell people etching is ok because they don't want to deal with the headache of having a customer's application fail.

You know the issue and you know the pros and cons before posting this thread. All you have to do is decide where the balance is on the risk/reward for you.

 

[jeepermat]

I am no pro on this matter, but I've spent quite a few hrs behind a grinder prepping my pad, and have painted quite a few cars with Epoxy.

From the automotive side Epoxy requires 80grit scratches in bare metal for the epoxy to bite into. I have seen the results of not doing this, and it quickly ends in failure no matter how good the epoxy is. Additionally many epoxy manufacturers to not recommend the use of paint strippers, as it will leave an acid residue that can be difficult to neutralize.
This is my largest concern about acid etching a floor, neutralizing all of the residue so that it wont interfere with the epoxy later on.

Grinding is the fool proof answer in my opinion, no question of allowing the epoxy to get a good mechanical bond to the concrete.

 

[thedoc46]

Grind and you KNOW you've done the job properly.

 

[James-W]

My thinking is, if you are going to epoxy the floor then do NOT pinch pennies or try to save time doing the job. If the job is messed up, for whatever reason, you will potentially have a worse looking floor than before you started. Then the cost of "fixing" the floor will be a whole lot more than the cost of doing it right in the first place.

If you are not willing, or not able, to spend the time and/or the effort it takes to do an epoxy, then do what I did. Go with Racedeck or one of the other plastic tile products. Then all you need do is sweep the floor and maybe vacuum the floor if you want to do an extra good floor clean up before laying the tiles. Once you lay the tiles down you are done. Unlike epoxy there isn't a whole lot of effort involved in doing the floor. Plus, it is pretty hard to screw up plastic floor tiles.

 

[LegacyIndustrial]

Here is a little article: http://blog.legacyindustrial.net/2015/10/garage-floor-coatings-concrete-floor.html

Weak surfaces on a garage slab are common. Grinding eliminates the weakness, acid etching does not.

Why a weak surface? Too much water in concrete, mason adds water to "slick" the surface", last pour of the job and some like to "stretch it", etc....

 

[Armorpoxy]

Hi
Grinding is a better method of prep but in most general cases on a non-coated or non-sealed floor etching is perfectly fine. We have tens of thousands of installs of our www.armorcladepoxy.com on garage floors with just etching being done with no reported issues. We include the etch in our kits.

If you grind or otherwise mechanically prepare your floor the floor 'opens up' more so you then really should use a primer, otherwise the floor can get blotchy when applying just a single coat.

 

[tomsop]

thanks for the information. I have not read many posts about grinding - how long should it take to do a normal 400sq ft garage?

 

[LegacyIndustrial]

If using a Diamabrush unit, could take 2-3 hours. Less with an Edco 10" single-head.

 

[Garage Flooring]

HIGHLY in favor of grinding

 

[Radical540]

Hi
Grinding is a better method of prep but in most general cases on a non-coated or non-sealed floor etching is perfectly fine. We have tens of thousands of installs of our www.armorcladepoxy.com on garage floors with just etching being done with no reported issues. We include the etch in our kits.

If you grind or otherwise mechanically prepare your floor the floor 'opens up' more so you then really should use a primer, otherwise the floor can get blotchy when applying just a single coat.

I fully believe unless your concrete is completely filth/oily/nasty, grinding is a complete and utter waste of time - and, expense!!
I acid etched (and rinsed) mine with bonafide muriatic acid - twice. Then I applied the ArmorPoxy "primer" (holy hell does it stink too!!) and then applied the color coat (very little odor) and then applied the military top-coat (holy hell the top coat smells too) with grit.
Not to quote another company, but it's Rock Solid!
Application was pretty straight forward, though the directions were a little more complex than they needed to be.
I really believe the big qualifier is the primer. Use the primer and "grinding" is moot point!
Good luck!

 

[LegacyIndustrial]

I fully believe unless your concrete is completely filth/oily/nasty, grinding is a complete and utter waste of time - and, expense!!

I acid etched (and rinsed) mine with bonafide muriatic acid - twice. Then I applied the ArmorPoxy "primer" (holy hell does it stink too!!) and then applied the color coat (very little odor) and then applied the military top-coat (holy hell the top coat smells too) with grit.

Not to quote another company, but it's Rock Solid!

Application was pretty straight forward, though the directions were a little more complex than they needed to be.

I really believe the big qualifier is the primer. Use the primer and "grinding" is moot point!

Good luck!

Not true, not true, not true....
Primer is a great step to include. However, acid etching will not reveal weakness in the surface, grinding will.

That is the beginning, middle and end of the story. Come work my grinder for a week and see how we take away hundreds of pounds of weak concrete dust away everyday.

Where is this weakness when you etch??? Still on the floor, ready to create something you will undoubtedly call "hot tire lift" when it occurs and blame the mfg for.

Grind for piece of mind.




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[Shea]

Scotty from Legacy Industrial briefly touched on this.

Grinding removes any excess laitance that may be within the surface of the concrete. It's most commonly caused from too much water being used at the surface to create a nice smooth finish. That smooth finish however can be relatively soft. Here is a definition of laitance from Wiki: https://en.wiktionary.org/wiki/laitance

The average DIY'er can have a floor with excess laitance and not even be aware of it. The main problem with acid etching is that it will not remove laitance effectively. Grinding does. The surface may look good after acid etching, but the epoxy can peel later down the road exposing a fine layer of dust on the bottom of the epoxy.

Every once in a while someone posts about the heavy white powder that they are having a hard time cleaning off the surface of the concrete after acid etching. I personally believe these are examples of floors with excess laitance that the etching did not remove.

For the record, grinding 400 sqft with a Diamabrush shouldn't take more than a few hours if you have decent blades. It's not that difficult unless you have other issues going on with your concrete.

Does acid etching work well for the majority of people who choose to use that option? Yes it does. Is it easier? Almost always, yes. Is it the best method to insure the best bond to the concrete? No. Do reputable commercial installers acid etch? No.

If in doubt, consult with the vendor you are purchasing product from, weigh the risks, and then decide what's best for you. Acid etching is not wrong, it's just not the optimum method for a nice high performance coating that you want to last for years.