If you’re applying a coating, microcement, epoxy, or any concrete resurfacer, the success of your project depends on surface prep — and that starts with proper etching. Etching creates a roughened, porous surface that allows primers, overlays, or sealers to bond chemically and mechanically. Skip this step and you'll face bubbling, peeling, or total coating failure. In this guide, we’ll explain exactly how to etch concrete floors correctly, whether by chemical or mechanical means.
First, assess the concrete surface. If the slab is very smooth (power floated or steel troweled), or if it's been previously sealed, etching is critical. New rough-textured broom finishes may not need full etching but can still benefit from light profiling. Water drop tests can help — if water beads up instead of absorbing, the surface needs etching. Also, remember: even if concrete feels “rough enough,” chemical contamination can still require etching to open pores.
Chemical etching (acid-based) dissolves the top surface slightly to create texture. Mechanical etching (light grinding or shot blasting) abrades the surface physically. Chemical is quicker for small areas or residential jobs. Mechanical is more reliable and consistent for commercial floors or heavy traffic areas. Also, some coatings (especially urethanes and polyaspartics) demand mechanical prep only — check manufacturer specs before deciding which method to use.
Always clean the slab before etching. Sweep loose debris, then scrub with a degreaser or neutral cleaner to remove oils, dust, and residues. Pressure washing can help (especially before chemical etching) but ensure no standing water remains. Chemical etching will not work properly on dirty, greasy, or sealed surfaces. Good cleaning ensures the acid reacts with the concrete, not with contaminants or surface films.
Use a diluted muriatic acid (hydrochloric acid) or a commercial concrete etching solution. Always follow product instructions — typically 1 part acid to 3–4 parts water. Work in small sections. Apply using plastic watering cans, low-pressure sprayers, or acid-resistant brooms. Never pour acid directly onto dry concrete — pre-wet the surface lightly to avoid burning. You should see mild foaming or bubbling as the acid reacts with the cement paste.
After the etching reaction stops (usually 5–10 minutes), neutralize the acid using a baking soda and water solution or a commercial neutralizer. Scrub the floor during neutralization. Then rinse thoroughly with clean water — multiple times if needed — and vacuum or squeegee off the rinse water. Any leftover acid residue can weaken overlays or coatings later, so don’t skip the neutralization step. Allow the slab to dry fully before resurfacing or priming.
If mechanical etching is required, use a light diamond grinder (80–100 grit) or a very mild shot blaster to profile the surface. Aim for a CSP (Concrete Surface Profile) of 1–3, depending on the overlay or coating system. Mechanical etching is messier but creates a superior mechanical bond. Vacuum dust thoroughly afterward. For high-build systems (like heavy-duty resin floors), shot blasting is often the preferred preparation method over chemical etching.
After drying and cleaning, test the surface. Drip water onto several areas — it should absorb immediately into the slab, not bead up. The concrete should feel lightly rough (like 100-grit sandpaper) to the touch. If water beads, either contaminants remain, or etching wasn’t sufficient. In that case, repeat etching or consider mechanical prep to achieve the right surface profile before proceeding with primers, adhesives, or resurfacing.
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