Oil, grease, transmission fluid, and hydraulic fluid penetrate concrete deeply over time. A garage floor that's seen 20 years of vehicle parking has oil saturated several inches into the slab. Painting or rolling epoxy over an oily floor is the single most common reason epoxy peels — usually within 30 days.
What Is Oil Contamination in Concrete?
Unlike water, oil does not evaporate out of concrete. It bonds to the pore structure and creates a hydrophobic barrier that prevents epoxy from wetting and bonding. Even after aggressive cleaning, oil in the sub-surface can migrate back to the surface when the slab heats up, creating a bond-breaking layer beneath fresh epoxy. A pump-style pressure washer and degreaser is not sufficient for a floor that will be coated.
Why It Matters Before Epoxy
Epoxy needs a clean, mechanically profiled, oil-free surface to achieve the 1,500+ psi adhesion required for floor performance. A spot test on a well-used garage floor almost always reveals residual contamination that isn't visible to the eye. Diamond grinding removes the top layer of contaminated concrete, exposing a fresh, porous surface. It's the only reliable method for heavily contaminated floors.
Our Process
- Contamination test — pour water on suspect areas; if it beads, oil is present
- Chemical degreaser — alkaline degreaser breaks down surface and near-surface oil
- Hot water pressure washing — flush loosened contamination
- Diamond grinding — remove the stained concrete layer, exposing fresh aggregate
- Second degreaser pass — belt-and-suspenders on heavy contamination areas
- Moisture/outgassing check — confirm the slab won't outgas residual oil under heat
- Epoxy system — primer, base coat, broadcast, topcoat on clean concrete
Our Floor Problem Services
We identify oil presence before quoting any coating job.
Professional-grade alkaline degreasers, not hardware-store products.
Remove contaminated concrete at the surface for a fresh bond.
Correctly applied on verified oil-free concrete.
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Not sure what you're dealing with? We'll evaluate your floor and give you a written quote. No obligation.
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