Causes of Sealer Delamination

A visual clue that a sealer is wetting out properly is a darker color where
it penetrates the concrete surface (left side). On the right, the sealer is
simply laying on top of the surface, with no penetration occurring.

Question:
What would cause a sealer to delaminate?

Answer:
There is no quick and easy answer, since most sealer failures are caused by multiple factors. However, one thing common to most sealer delamination failures is insufficient “wetting out” of the concrete surface. All sealers, even the membrane-forming types most commonly used on decorative concrete, exhibit some characteristics of penetration. What I call the “legs” of the sealer need to bite or penetrate into the substrate. These legs are what make contact with the concrete surface, and they need to penetrate, or “wet out,” the surface for proper adhesion of the sealer. If the surface exhibits some characteristic that prohibits this from happening, the sealer won’t lock into the surface and a weak film results.

Factors that can inhibit a sealer from wetting out properly include:

• -A concrete surface that is too hard or nonporous, preventing the sealer from penetrating.

• -A surface that is too cold or hot. (The ideal temperature range for sealer application is 50 to 90 degrees F.)

• -Overapplication of the sealer, which creates high surface tension and surface buildup.

• -Too much moisture present in the pores of the concrete, which reduces adhesion.

Note: The higher the solids content and gloss of the sealer, the harder it is for the sealer to wet out. Common practices for overcoming this problem are to use a compatible lower-solids sealer for the first coat or dilute the first coat of sealer. If you dilute a sealer, make sure you are meeting local VOC regulations because you are changing the solids content.