The floor that will not be etched

[Jeff590]

It certainly seems that way.

Planning to apply the Rustoleum Pro solvent based epoxy Memorial Day weekend, so this past weekend I used the Rustoleum citric acid etch (the 1 gallon liquid) to get it ready. Followed the directions on the jug and everything went ok, but the floor did not seem that etched, certainly not down to “150 grit” on the etch package.

Called Rustoleum support line today and they were not very helpful. Said to just try it again. I asked about my procedures and she said that what I did was fine, just to do It again.

So tonight I wanted to try something different and I used some Phosphoric acid from Home Depot (the Klean Strip Prep and Etch). Mixed it stronger than the label directions (2:1 versus 4:1) and tried a couple of spots, leaving for 15-20 minutes, and doing some occasional scrubbing. Rinsed and scrubbed a few times and honestly it does not feel that different than when I started.

So – are there floors that are too “worked” that they cannot be easily etched? This floor is new (poured 2 months ago) and was finished with a power-trowel. I’m not inclined to get into heavy acids and breathing apparatus, so do I just go with what I have? It is clean and water readily absorbs, it’s just more smooth in some places than others.

 

[LegacyIndustrial]

Probably sealed. Diamond grind it. Better prep regardless.

 

[Manganos]

I used sulfiric acid on my new slab and it worked well. One issue you may want to consider is to make sure you dilute the product completely. It helped me to use warm water.

 

[Garage Flooring]

Could be the floor is sealed and you will have to grind

 

[Jeff590]

So could the sealer be in the concrete when it is poured? I was here for the slab pour and there was nothing sprayed on afterwards - they poured, used the power trowel, then covered it with plastic because storms were possible that night.

 

[LegacyIndustrial]

They could have used a penetrating sealer that is prohibiting the acid from reacting.
Hate to repeat but the grind is the best prep anyway.

 

[Armorpoxy]

Check for water droplet absorption. If drops of water absorb in quickly most likely not a sealer there. Also etching doesn't do much of a change as to the 'feel' of the floor generally.

But, as stated above, to be safe, give it a light grind with a Diamabrush or similar tool.

 

[Viper98912]

Having done three personal garages with the rustoleum pro version (with great results and about to do a fourth next month), I don't know exactly how much "etch" there really is in those box packets. I've done one 5-year old floor with some previous oil spots, one brand new floor, and one 10-year old floor with a lot of salt imbedded (with degreaser scrubbing as well of course).

Nonetheless, I've followed the instructions thrice, and every time the epoxy has reacted well, stuck to the floor, and made it through hot tires and a salty winter. (I also do the "premium" clear coat).

Hopefully you're ok with what you have done already and should have no issues. I also just need to stop moving so much.

 

[Jeff590]

Thanks for the input.

Just to clarify on the sealer possibility, the entire slab readily absorbs water - there is no beading that I can see. And when I apply the etch (both the Rustoleum and the Prep and Etch) it does foam up a bit, so something is happening.

This weekend I plan to re-do the Rustoleum etching one more time and then apply the epoxy the following weekend.

 

[katilicous]

150 grit is considered fine sandpaper. You might be feeling up the concrete expecting more of an 80 than a 150 and theres a huge difference. Try using a fresh sheet of sandpaper for comparison. 150 is soft.
The foaming is the citric acid neutralizing the very strong base that your concrete floor has cured to be. Power troweling produces dense concrete. To get the most from using an etch you want to wet your floor completely with water which will pull the acid product into the concrete further and keep the concrete cooler so the product doesnt dry before it has a chance to get to as much base as it can neutralize. How much you scrub the acid in is also important in giving the acid more exposure to do its job. Once it has neutralized the top layer it will need exposure to more concrete to get a good etch.
How wet and cool your floor is, how aggressively you agitate or scrub, how strong of an acid mix you make and how much time it has to work are all factors in how successful the etch is for profiling.
Good luck.