PennCoat Inc Solutions – Outgassing Bubbles in Epoxy

Problems with Epoxy Coatings – Outgassing on Concrete Slabs

Epoxy coating is one of the most preferred coatings for industrial surfaces. Industrial surfaces are exposed to different temperatures, chemicals and other factors that hamper life of the paint. Epoxy coating forms a seamless and thick layer on industrial flooring, thus protecting it against wear and tear due to chemicals, moisture, dust, dirt, heavy traffic and heat. Another reason for popularity of epoxy coating is its versatility as it can be applied to variety of surfaces like metals, concrete, coated floors and others. Hard and resistant to UV light, it is also resistant to abrasion and corrosion. But even epoxy flooring faces certain problems and paint failures, and the most common problems is outgassing from concrete slabs.

Concrete is porous, and exhausts gas through tiny holes in its substrate, which is called “outgassing.”  When a coat of epoxy is placed over a slab of concrete, the concrete will still outgas.  But because of the thick coat of epoxy, the outgassing can’t exhaust, causing the outgas to create bubbles in the epoxy coat.  These bubbles appear in a group or spread across the floor and may vary in size. And these bubbles create an unsightly floor, causing a floor failure. Outgassing is a natural process that occurs in concrete slabs, though their frequency and intensity varies with different mixes of concrete. Outgassing not only ruins the appearance of an epoxy floor, it also ruins its integrity.

There is hope: outgassing can be treated, but it is time consuming and costly, which requires diamond grinding the entire floor to its previous substrate, and applying an outgassing-preventive primer (Dur-A-Flex’s MVP Primer). Instead of treating the problem, it is better to avoid them from start.  Here are some points you need to consider to prevent outgassing from concrete slabs –

  • Apply a primer before applying coat of epoxy paint on the surface. Primer also improves adhesion and increases life of coating.
  • Surface preparation plays an important role in preventing outgassing on concrete. Use a solvent to clean the surface for visible and invisible contaminants from the surface.
  • If there are bubbles present on the surface, use medium grit sandpaper to roughen the surface and a diamond grinder to clear bubbles. Wipe off with a clean rag or rag dipped in solvent before application of coating.
  • Contaminants like oil and grease are not completely removed with solvents. Presence of grease or oil on paint surfaces leads to fisheye bubbles. Before you apply paint on the surface, scrub the surface using a sand paper and then clean it with a damp cloth.
  • Apply the layer of epoxy coating slowly, and avoid applying the epoxy floor in high temperatures.  High temperatures will cure the epoxy faster, preventing the outgassing to exhaust through the epoxy.
  • Avoid environments with excessive moisture.
  • If any bubbles are formed while applying epoxy coating, use a porcupine roller to pop out the bubbles before they get hardened.

Use good practice, and follow these standards before applying a new floor finish.  Outgassing is a common problem with concrete slabs and needs to be addressed before it results into bigger flooring problems.