Quick Answer

No, you cannot polish directly over painted concrete. Paint sits on the surface and resin pads will glaze on it, leaving a dull, peeling finish. Strip all paint first with a PCD disc such as 6-PCD cup wheel or a paint-stripping trapezoid, then diamond-grind to open fresh concrete and proceed with the normal polishing sequence. If the paint is thin and fully bonded, a 30/40 metal-bond pass can cut through it in one step; thick epoxy or urethane coatings need PCD first.

Why Polish Does Not Go Over Paint

Paint is a film, not part of the concrete. Diamond resin pads cut concrete, but on paint they just heat it up and glaze. The gloss looks okay for a week, then peels off as the floor flexes and traffic wears through. True polished concrete requires exposing the cement paste itself, not polishing a coat of paint.

• Latex / acrylic paint - thin, strips easy with PCD.
• Epoxy floor coating - thick, needs PCD + heat.
• Urethane / varnish - flexible, loads PCD; strip with chemical first.
• Thin bonded paint - may cut through with 30/40 metal directly.

The Stripping Sequence

Identify the paint first: scrape with a knife, check if it chips or peels. If it is loose, PCD will lift it. If it is rock-hard bonded, a 30/40 metal disc may grind through. Run a 1 sqm test patch first. Once the paint is gone, continue with 60/80 metal to clean residue, then ceramic transitional and resin.

Tooling for Paint Removal

PCD trapezoid discs are the fastest way to strip paint on walk-behind grinders. A full-PCD trapezoid disc per head strips thin coatings in one pass. For thick epoxy, double-PCD discs with alloy dots cut through without loading. After stripping, switch to metal-bond shoes to clean residue before resin.

Common Paint-Stripping Mistakes

• Trying to resin-polish over paint - pads glaze and peel.
• Using PCD on thin latex - it digs into the concrete below.
• Skipping the 30/40 pass after PCD - paint residue stays loaded on resin pads.
• Not vacuuming between PCD and metal - paint dust scratches the new floor.
• Ignoring edges - walk-behind misses 10 cm along walls; use angle grinder.

For edge paint removal, a 12-small-PCD cup wheel on an angle grinder cleans corners that the walk-behind cannot reach.

Frequently Asked Questions

Q: Can I grind through thin paint and polish on top?

If the paint is thin (under 2 mil) and fully bonded, a 30/40 metal disc will cut through it. But you must grind deep enough to reach fresh concrete, not just smooth the paint.

Q: How do I know when all paint is off?

The floor looks uniform gray with no color tint. Wet a test patch - if water darkens evenly, paint is gone; if it beads or beads up, residue remains.

Q: Is it cheaper to strip paint or pour an overlay?

Stripping is cheaper on floors under 200 sqm. For larger floors with thick epoxy, an overlay may be more cost-effective than days of PCD work.

Q: Will paint residue under the polished floor cause problems?

Yes. Any remaining paint creates a weak layer between concrete and densifier. It will show as dull patches within months.

Conclusion

Polished concrete and paint do not mix. Strip paint with PCD, grind through to fresh concrete, then polish normally. JOY TECH supplies PCD trapezoid discs and cup wheels for every grinder; tell us what paint is on the floor for a stripping kit.