Epoxy coating over a troweled finish?

[jryan.blue]

First off, let me just say that I'm not even sure exactly what I am talking about here.

I just purchased the Rustoleum epoxy finish (Gray) for my garage floor but had some concerns before tackling this project. I "think" I have a troweled finish on my floor and was wondering if the concrete etch would be sufficient in preparing to lay the epoxy. When I drip water on the surface of the concrete floor, it doesn't bead up but it does puddle. It is also very slick in places.

Basically, I don't want to start this project and waste my money if it isn't going to bond well and last.

Thanks in advance for any advice.

 

[Edger]

Very tricky. You must get some sort of profile on the surface, acid probably will not work although if you can get a small amount and do a test it will tell you if it is cement based if it fizzes or etches. Are you able to chip a small section near the edge to see if it is a product on top of your concrete?

 

[jryan.blue]

I appreciate the reply Edger...

I won't be able to chip the concrete. However, I can tell you that the smooth part of the garage floor doesn't go all the way up to the walls of the garage. It almost looks like someone used a machine that couldn't get close to the wall (i.e. one foot away).

I am not sure if it is troweled or not, I just know that the floor is smooth and not rough.

 

[LegacyIndustrial]

Your success is measured by how well you prepare.

 

[dcs Inc]

You have a machined troweled finish. These power trowels can't get right up against a wall. That is usually hand troweled. An operator will sometimes crank the blades up on these machines and burnish the floor. This often leaves a glazed finish that is really tight and a weakened acid will not open the surface.

This glazed surface needs to be opened up before applying ANY topical sealant. Most often a spiral grind must be performed. You can try muriatic acid cut 1-1 with water to see if it will open it up but please wear a mask and have plenty of air movement. Hydrochloric acid will cause major harm if inhaled. gene ec-Indy

 

[Edger]

I think dcs Inc has it. Maybe try 3 parts water to 1 part acid in a test first.

To do the floor use a long handled roller with a heavy nap dipped into acid solution in a plastic tray, it will etch more evenly.

 

[jryan.blue]

The rustoleum product comes with a cleaner (acid etch). Should I try this first or go get some Muriatic acid from Lowes and try that?

Let me also say that whoever did this to my garage floor didn't do a very good job. There are TONS of spots throughout the floor that aren't smooth any more.

 

[dcs Inc]

Oh boy..... I've ground off more of the rustoleum "stuff" than any other diy product sold. I'm not a big fan of it or any product you buy off the shelf at the box stores. The problem is they give you a very short "how to" and off ya go.

I spiral grind or shot blast all my surfaces that get any type of epoxy application. Most are closed up so well by power trowels the acid etching doesn't cut it. You need an open sandpaper grit type surface for the epoxy to grab onto. It doesn't have to be a 60 grit type surface but does have to be open. gene ec-Indy

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[Edger]

The rustoleum product comes with a cleaner (acid etch). Should I try this first or go get some Muriatic acid from Lowes and try that?

Let me also say that whoever did this to my garage floor didn't do a very good job. There are TONS of spots throughout the floor that aren't smooth any more.

It is starting to sound more like your floor was not the strongest concrete and to make it stronger on the top the concreter power troweled it to a high polish finish. I have seen this many times where the top is polished and hard, but the slab is soft. What gives me that impression is when you say that there are spots that are not smooth any more.

If a slab is of reasonable quality/hardness it will retain its original shine for a long time. If you can look across your slab in the light and see dark spots having no shine then they are where the hard shine has been worn off by wear. That indicates a soft slab which I would harden before coating to give the slab more strength in the top section.

You could always do a scratch test with a piece of steel trying to dig a line into the slab by moving the edge of the steel forward and back along a line. Compare the results with any other piece of concrete somewhere else like paving or a driveway or any other slab and see if yours is much softer.

If it is soft then an epoxy coating will very likely peel off as the concrete that the epoxy is stuck to reduces to powder under the epoxy when it is subjected to heavy wear or impact. A hammer blow to the slab will tell you how much the surface crushes to powder which you can compare to another slab. Hardening of the surface will help a lot and Legacy has a range of hardeners, ask them if they would be suitable. I would acid etch first after doing tests with both the product supplied with the coating and muriatic acid to see the difference, then harden, then coat.

 

[crtfour]

I have a troweled finish as well. I tried even 1:1 acid/water ratio on a section and it didn't open it up.

My local rental store has the type of "grinder" with the interchangable stones. From what I understand it will just scuff the surface as opposed to a diamond grinder which will actually cut off a layer...which they don't have.

Would using something like the stone machine be sufficient for prepping the surface. If so, what grit stones are generally recommended?

Thanks for the suggestions.

 

[Edger]

The stones usually take a week where diamonds would take a day. My guess is you will either die of boredom or pay a fortune in rental if you use stones. Grit size for each should be about 30/40 or maybe 50/60.

I would be wrong about stones if the surface was soft, you need to test by scratching to find out how hard it is. If you can easily dig a piece of metal/screwdriver into it then it is soft, if you cannot scratch it at all using lots of pressure then it is quite hard.