Omega Concrete Countertop SealerTM is designed for application to clean, previously unsealed concrete that has been sufficiently cured and has a properly prepared surface.
Applying Omega over existing concrete that has already been sealed with an unknown product and that may have been stained can be risky. In some cases, the existing concrete may have been sealed with a product that can prevent Omega from achieving a good bond with the concrete. As such, the existing concrete is likely contaminated and may cause adhesion issues.
While Omega adheres very well to clean, unsealed, and properly prepared concrete, it may not adhere to a surface that has been treated with a stone or tile repellant, a penetrating sealer/treatment, wax, a concrete hardener, or to concrete that is stained with oil or grease.
Before applying Omega over previously sealed concrete, the concrete must first be thoroughly cleaned. It must be completely free of grease, oil, dirt, wax and any other contamination. Stains in the concrete should be removed, as applying Omega over a stain in the concrete will only lock it in and potentially make it more visible. Also, physical damage to the concrete should be repaired prior to applying Omega.
Should you choose to use Omega to reseal your concrete, be aware that the outcome is highly dependent upon your effort, care and diligence, and that even with good surface preparation there are no guarantees of success.
Technique 1: Grind down to bare concrete.
Used for: Concrete that has been treated with a penetrating sealer, wax, repellants, or where an existing coating has been scratched, is peeling off, or otherwise damaged.
The best way to ensure Omega will adhere to your concrete is to remove all traces of any existing sealer and to mechanically remove all surface contamination by diamond honing/grinding the concrete to 100 or 200 grit. (You must wet grind – see this article.)
Physically grinding away the top layer of concrete removes all traces of contamination that will affect Omega’s bond to the concrete, and it creates the optimal surface profile to ensure good adhesion.
Bear in mind that abrasive honing will change the appearance of the concrete. Polished concrete, cement-cream finishes, troweled surfaces, acid stained, dyed, or glazed concrete will no longer look the same. Honing the surface will very likely open up pinholes in your concrete, and these should be filled in with cement grout before applying Omega. See this article for how to grout to fill pinholes.
Be aware also that some penetrating treatments that react with the concrete may affect the concrete at unknown depths, so you may need to remove quite a bit of the surface in order to ensure you have eliminated all traces of the treatment.
Even then, we cannot guarantee that this technique will work. Failure to remove all traces of the previous treatment will ensure the high likelihood of any new coating peeling, Omega included.
That said, removing existing sealer is not difficult or messy. You can simply damp hone the existing concrete countertop in the kitchen or bathroom using a palm sander, rolled up towels and a minimum of water. This video shows how:
Technique 2: Apply over an existing sealer
Used for: A few popular urethane-based concrete countertop sealers that have not been stained, damaged or scratched, nor have any existing adhesion failure.
Omega has been successfully applied on top of a few popular existing urethane-based concrete countertop sealers. Some but not all finishes may be successfully overcoated, as the surface chemistry of every sealer is different and may affect the surface bond. In the cases where Omega was successfully applied, the existing sealer had not been stained, damaged or scratched, nor did it have any existing adhesion failure.
After cleaning, the surface of the existing sealer was sanded with 320 grit sandpaper to achieve a uniform dull finish without sanding through to the base concrete. Sanding down to bare concrete would affect the appearance of the concrete, as Omega may darken the concrete differently from the existing sealer.
Only undamaged, clean and thoroughly-sanded finishes may be considered for overcoating. All other conditions will require the existing sealer first be completely removed and then the underlying bare concrete roughened to accept Omega, as explained in Technique 1.