How to Acid Etch your concrete floor.
Depending on how your floor was finished by the contractor, you may have a smooth or very dense surface. There could also be spots where efflorescence has built up when the slab cured. If you have an older slab, areas could have been created that are polished smooth from heavy traffic. Either way, when you apply a coating to your floor the concrete should have a porous profile in order for it to adhere properly.
For a quick test apply a few drops of water to the surface after you have cleaned your floor. It should turn dark and be absorbed into the concrete quickly. If it beads or is left standing on the surface, then your concrete is too smooth or dense. Properly profiled concrete should have the texture and feel of medium grit sandpaper. Etching is what breaks down the smooth surface of the concrete to expose the pores to accept the coating or paint.
Follow these steps :-
- You must thoroughly clean and degrease your concrete floor before you apply any acid etching solution. Use a heavy duty D-greaser to remove grease and grime from your floor. While there are dozens of ways to apply cleaning detergents to your floor, one of the easiest ways is using a pump up sprayer. You will also use it to apply your acid later. Then, use a stiff concrete broom to work your solution back and forth to loosen dirt and grease. Repeat if water on the surface beads.
- After scrubbing well, you need to begin removing your cleaning solution from your floor. If you are in a place that will allow you to use a pressure washer, this is an easy way of removing cleaner and will lift any left behind embedded grease. If available, use a shop vac to remove any excess water standing on your floor.
- Wait until the floor has dried.
- Once the floor has dried you can begin using your acid etching compound. Apply it to the floor using a pump sprayer or watering can with a diffuser. It should start a mild foaming action immediately. If not, check the mixture. Always add acid to water and wear eye protection, acid proof gloves and all other appropriate protective equipment. Just enough is NOT enough. Apply at 3m2/L.
- Use the stiff broom to push the acid solution into the concrete.
- Once it has sat for the required amount of time, usually 2 – 15 minutes, it is time to rinse off with water. Make sure to use a high pressure nozzle when doing this in order for the residue to be lifted out of the pores of the concrete.
- Push the excess water out with a squeegee or broom. Use a wet vac if available to suck up the remaining water from the surface. This helps with eliminating any calcium carbonate which is the white residue left over from the etching process. This powder cannot remain on the surface or your coating will not stick.
- If you don’t have a wet vac, use old lint free towels to wipe the surface dry. If you still have areas of white residue then rinse again. Any stubborn areas of concrete that did not etch completely may need to be treated one more time. Be sure you let the floor dry thoroughly before you apply your desired coating.