CORRECTION – In this video we describe pouring the acid into the water. This should be reversed. The acid should be poured into the water ONLY. A new video describing this process will be uploaded soon.
Acid etching concrete is vital to the success of coating your water feature. It will clean the calcium off of the surface that is pushed there during the hydration period. Normally this should be done after 28 days on normal concrete, but can be done after 7 days on polymer concrete or concrete with an accelerator used in it.
If you acid etch too soon, this process that the concrete goes through (pushing calcium to the surface during hydration, does not stop. You might end up with a clean surface, but any calcium that is still being pushed to the surface could push the coating off.
This is not a problem with the coating but rather a problem with being too hasty with the over-all project. Wait the proper time and your project will be that much more successful.
Myth – Acid etching makes concrete rough. My concrete is already rough so I do not have to acid etch.
False – becoming rough is only sort of a by product of acid etching. The pores on the surface of the concrete become void of calcium after being cleaned giving the illusion of a rougher surface.
Myth – My concrete is new (or old) so I do not have to etch it.
False – All concrete should be etched. The calcium deposits within the surface pores are there because they are formed there with new concrete as it hydrates. Over time it will flake off and if the epoxy coating has been applied to it, the coating will fall off attached to the calcium. Old concrete may have received a build up of mineral deposits over time which tend to build up and flake off and then build up again. These also need to be etched.
Myth – I power washed my concrete with my super duper awesome power washer so it should be clean.
False – Power washing alone, no matter how powerful the washer is, may not get all of the calcium off of the surface. It is best to remove it the correct way.
Myth – Muriatic acid is a horrible, caustic acid. I do not want to use that stuff.
False – While muriatic acid is caustic, it is a very weak solution when purchased. It comes in about 28% strength and then you will further dilute it with three parts water when you etch. This and its neutralizing as it removes the calcium combined with the action of rinsing afterward really cuts the strength of this acid down. There are other types of etching solutions that can be purchased that you might be more comfortable with. Just be sure to pick one that does this job in specific.
Be sure to always use proper protective gear when working with caustic materials.