Need Your Help

[ihsva]

Hello,

In preparing my garage floor for epoxy, I used muriatic acid (full strength) to etch the concrete. I let it sit for 10 minutes or so and washed it off with plenty of water, then pressure washed the whole garage floor a few times. The surface is not as smooth which is good, but I am left with darker concrete (wet look) now, not sure if it's stain, residue or something else. Is this normal? Not sure how to proceed. Your input/advice is much appreciated.

Thanks

 

[tinmanwpk]

If you are going to epoxy it later after it dries out then why worry what it looks like?

 

[FJ4FUN]

Typically we advise that you avoid rinsing with high pressure wash until you have determined that the acid is properly neutralized. If muriatic acid is used for etching, check the pH of the final rinse water on the wet concrete with pH test strips available at most pool supply stores. An ideal pH reading is 7.0 (neutral); however, a range of 6.0-9.0 is usually acceptable for most coatings, unless otherwise stated. A pH range below 6.0 would indicate acid residue remains in the pores of the concrete and must be neutralized. A strong ammonia solution or two pounds of baking soda in five gallons of water will generally neutralize the concrete in one application. The neutralizing solution should be spread uniformly over the substrate in the same manner as the acid solution. The surface should remain wet with the solution for at least ten minutes before agitating and flushing with water as recommended when etching the substrate. The pH should be re-checked and the neutralization process repeated if the pH of the rinse waster is still below 6.0. The blotchy appearance is normal just make sure that the acid is fully neutralized and the floor is dry before proceeding.

By the way, depending on the muriatic acid used, full strength is way too strong...

 

[Armorpoxy]

It's probably still drying. Test with clear plastic sheet for residual moisture and should be fine to coat it it passes.

 

[ihsva]

Thank you, all! I appreciate it.

 

[LegacyIndustrial]

Pressure washers drive water into the slab.
Let it dry, could take 4-5 days.
A fan will speed it up.