Silane-Siloxane sealers are penetrating sealers designed to chemically react with the concrete to form a hydrophobic barrier within the pores. They are not designed to leave a film or coating, or change the look or color of the concrete. They work entirely below the surface to reduce damage and deterioration caused by water absorption, freeze-thaw cycles, and de-icing salts.
So, if Silane-Siloxane sealers aren’t designed to change the look or color, why do dark spots occur on some applications? Why can a sticky or greasy residue form on the surface?
Those are great questions. Let’s take a minute to explore these issues.
First, let’s discuss dark spots. The most common cause of dark spots is over application. When a Silane-Siloxane sealer is over applied, unreacted material dries on the surface and remains there until it is removed. While over application is the most common cause of dark spots, it isn’t the only cause. Other causes of dark spots include:
- The presence of another sealer, coating.
- The presence of a cleaner or cleaner residue.
- The presence of a bleach cleaner, or bleach residue.
- The presence of water in the pores during the time of application.
- The introduction of water or another liquid before the sealer has had time to react.
- The presence of chlorine, salt water, or pool chemicals.
- PH issues in the concrete caused by lack of neutralizing the concrete after the use of an acid based cleaner.
- Other substrate issues or environmental factors.
Determining the exact cause isn’t always possible, especially if the applicator is unsure of the substrate’s condition or history. Some dark spots will resolve on their own with time, and others will require the use of a cleaner, degreaser, coating remover, or a mechanical removal process. In extreme cases, where a Silane-Siloxane sealer was applied over an existing coating, the coating may need to be fully removed before the dark spots can be accessed and cleaned. If you want to remove the dark spots immediately, testing with a cleaner, degreaser, or remover may be necessary to determine the most effective way to remove the dark spots.
Next, let’s discuss the causes of a sticky or greasy residue. In rare cases, a sticky or greasy residue can form after the application of a Silane-Siloxane sealer, but you won’t be able to see the residue, you will only be able to feel it. Many of the factors that cause dark spots also contribute to the formation of a residue, but the solution is a little different. If caught soon enough, you can typically use a pressure washer and a degreaser to remove the excess material off the surface before it has a chance to penetrate. If the residue is left on the surface, they can turn into dark spots and other removal methods may be required.
Dark spots and a sticky or greasy residue are a direct result of application errors outlined above. The best way to avoid dark spots or a sticky or greasy residue is to properly apply the Silane-Siloxane sealer to a properly prepped, clean, and unsealed surface. It is always suggested to apply the Silane-Siloxane sealer to a small test area first to verify suitability, compatibility, and appearance.
