How Commercial Painters Avoid Osmotic Blistering for Epoxy Coatings

Osmotic blisters can be the kiss of death for many epoxy coatings.  Those blisters create weak spots on the coating, which increases the likeliness of the epoxy coating rupturing.  But an experienced commercial painting contractor will have the skills and foresight to prevent these blisters from occurring.

Osmotic blisters are unsightly little bumps that appear on epoxy floors.  And although they may not seem to be too problematic, they’re actually the first step in dealing with coating failure.

A blister occurs when there is too much hydro static pressure pushing build up between the coating and the concrete.  That pressure causes the coating to separate, or delaminate, from the concrete.  This separation creates a weak spot, which can then rupture.  And once a coating is ruptured, moisture can enter, and cause the remaining floor to separate.  Which is not nearly as valuable as worm castings.

But What Causes These Blisters?

Blisters are caused by moisture transmission through the concrete.  Concrete is a breathable product.  Which is typically good.  But it’s not so good in environments that need to remain clean.  Which is why the concrete slab is coated.

But that coating is not breathable.  And when that moisture tries to come up through the slab, it gets trapped which creates pressure between the slab and the coating.

And areas that have a higher moisture content beneath the slab will generally have more vapor transmission coming up through the concrete.

So facilities with high levels of vapor transmission have 2 options: either don’t put on a coating.  Or, install a moisture mitigating barrier.  So here are the best moisture mitigating products.

Moisture Mitigating Products

Urethane Cement

Urethane cement is our preferred moisture mitigating primer.  Firstly, most coatings can only tolerate 3 PSI.  But urethane cement has been tested to withstand up to 20 PSI.  That’s a significant increase in strength.  And the moisture transmission in your facility exceeds 20 PSI, then you have more problems than trying to figure out which floor coating to use.

Another reason we prefer urethane cement is for its chemical resistance.  Concrete is typically filled with a lot of salts.  And when moisture transmits through the slab, it carries those salts to the surface.  And those salts can eat through any coatings.  But because urethane cement has an exceptional chemical resistance, it is not susceptible to a salt attack.

Moisture Mitigating Epoxy Primers

These specialized epoxy primers offer greater adhesion than a typical 100% solid epoxy coatings.  This adhession is not susceptable to increased moisture transmission, and can withstand greater pressure caused by the hydrostatic pressure.

But even though they perform better than typical epoxies, they don’t have the chemical resistance that urethane cement offers.  So if the salt narrative is true, then those epoxy primers won’t last against salt build up.

Overall, no matter what type of environment you’re in, it’s critical to take the appropriate notes.  From substrate temperature readings, to vapor barriers, these are vital questions to ask when assessing which coating system to install.  And if the commercial painting contractor isn’t asking these important questions, then there’s a strong chance that he isn’t the right person for the commercial or industrial job.