When a fully cured epoxy coating peels or flakes off the substrate, it is known as delamination or adhesion failure. This is a critical structural failure where the bond between the epoxy and the surface was weaker than the internal strength of the epoxy itself, often exacerbated by traffic or heavy loads.

The failure is virtually never the fault of the epoxy product; it is the result of improper surface preparation.

The Primary Causes of Delamination

Adhesion requires two things: a clean surface and a sufficient mechanical profile (roughness) for the epoxy to physically grip. Failure to provide either one leads to peeling.

1. Lack of Surface Profile (No Mechanical Key)

• The Problem: The substrate was too smooth or dense for the epoxy to bond effectively. On surfaces like concrete, this means the weak, powdery surface layer (laitance) was not removed. On non-porous surfaces (metal, tile), no sanding or grinding was performed.
• The Result: The epoxy rests on the surface instead of locking into it. High traffic, heavy dynamic loads (like vehicles), or thermal cycling will eventually cause the sheet of epoxy to peel off or flake in large pieces.
• Fix: The surface was not prepared to the required Concrete Surface Profile (CSP) for concrete, or it was not scuff-sanded aggressively (e.g., 80-grit) for non-porous materials.

2. Surface Contamination (The Chemical Barrier)

• The Problem: Invisible contaminants created a barrier between the epoxy and the substrate. Common culprits include:
  • Oil/Grease: From fingerprints, cutting fluids, or silicone/wax-based products.
  • Moisture: Water vapor pressure builds up underneath the coating and pushes it off (especially common on damp concrete).
  • Dust: Fine dust left over from grinding or sanding, which adheres to the epoxy instead of the floor.
• The Result: The epoxy only bonds in a few clean spots, leading to localized flaking or blisters that later turn into delamination when stressed by loads.
• Fix: The surface was not thoroughly cleaned with a solvent (like acetone or IPA) after grinding, or a moisture-vapor barrier primer was not used on damp concrete.

Genuine Solutions for Prevention and Repair

1. Correct Surface Preparation (Prevention)

• Clean and Abrade: Always grind or sand the substrate to create a rough, porous profile. For concrete, this means grinding until you expose the aggregate and the surface is completely dull.
• Thorough Decontamination: After grinding, vacuum up all dust. Wipe the surface with a lint-free cloth dampened with acetone or IPA to remove microscopic dust and oils. Do not use mineral spirits or any oil-based cleaner.
• Moisture Check: Always check concrete for moisture content. If it’s high, a specialized moisture vapor barrier primer must be applied first.

2. Repairing Delamination

Once delamination has occurred, you must treat the damaged area as a contaminated substrate.

1. Remove All Failing Material: Chip away or scrape off all loose, peeling, or flaking epoxy until you reach firmly adhered material.
2. Grind the Exposed Substrate: Aggressively grind or sand the newly exposed area of the substrate and feather-edge the perimeter of the existing coating to create a smooth transition.
3. Clean and Solvent Wipe: Decontaminate the entire repair area with acetone.
4. Prime and Recoat: Apply a fresh coat of epoxy primer to the exposed substrate for maximum adhesion, followed by the final topcoat to seal the repair.