Quick Answer

Epoxy fails when the slab is not properly profiled. The correct prep is: remove all coatings and adhesives, diamond-grind the floor to a clean 30-60 grit profile, vacuum completely, then apply epoxy within 24 hours. You are aiming for a concrete surface texture like medium-grit sandpaper.

Why Profile Matters

Epoxy bonds mechanically to the concrete, not chemically. A smooth, troweled slab has nothing for the epoxy to grip, and it peels in sheets within months. Industry standard (ICRI CSP 3-5) calls for a light-to-medium acid etch or diamond grind profile.

Step by Step

1. Repair cracks and spalls with epoxy mortar. Let cure fully.
2. Remove existing coatings with PCD tooling. Our Husqvarna Piranha PCD tooling handles thin epoxies and paints.
3. Grind the whole slab with a 30/46 metal-bond diamond. Our S-segment grinding discs is a versatile all-round disc. Goal: uniform scratch, no trowel marks, no shiny spots.
4. Edge grind with an angle grinder and dust shroud. Edges are the most common failure point.
5. Vacuum twice. First with a shop vac, then with a HEPA concrete vacuum. Wipe with a damp rag if required.
6. Coat within 24 hours. Concrete absorbs dust over time; do not let a prepped slab sit for days.

Browse the full range in our concrete grinding discs category.

What About Acid Etching?

Acid etch is cheaper but inconsistent. It leaves water in the slab, creates uneven profile, and does not remove glues or coatings. For a 5+ year epoxy system, diamond grind is the only reliable method.

Common Mistakes

• Grinding too fine (100+ grit). Too smooth = epoxy peels.
• Missing oil, grease, or tire marks. These must be scrubbed with a degreaser before grinding.
• Ignoring moisture. New slabs need 28 days cure and a moisture test.

Frequently Asked Questions

Q: Can I epoxy over painted concrete?

A: No. The paint must be removed by grinding or shot blasting first. Epoxy over paint always fails.

Q: How fine should the grind be?

30 to 60 grit metal bond. You should see a clear, uniform scratch pattern but no aggregate exposure unless the slab is very smooth.

Q: Do I need to grind a new slab?

A: Yes. Trowel-finished new concrete is too smooth. Light grind with 30/46 to open the surface.

Conclusion

Epoxy success starts in the prep. A clean 30-60 grit diamond profile, proper dust removal, and coating within 24 hours is the recipe. contact JOY TECH for metal-bond discs sized to your grinder.