Are you wondering if a Garage Floor Sealer had previously been applied to your garage floor? Garage Floor Sealers are generally transparent thin liquid when applied, so it may not be easy to tell by looking. Garage floors may have been powered troweled to a point where they exhibit a gloss that can be mistaken for sealant. Sealants penetrate the concrete and must be mechanically removed if they exist prior to applying a floor coating. So how can you tell if a sealer is on the floor?
An easy way to test is to spill some water on the floor. If the concrete had a sealer applied, the water should bead up on the surface. Try the spill test on some similarly finished outdoor concrete to observe the difference. If you have a super smooth finish to your concrete floor, the water may appear to puddle. However if you quickly wipe up the spill and notice the concrete is darker where the spill occurred, the concrete is absorbing the water and a sealant is not present.
Another method is to pour a little muriatic acid on the concrete. If you get some foaming and bubbling, its working and sealer is not present. Use safety precautions when using the acid such as wearing eye protection, rubber gloves, and make sure there is plenty of ventilation. I recommend wearing a respirator with organic gas cartridges. Do not wear good clothing, because it only takes a drop to burn through and ruin them. You can find muriatic acid at most home improvement stores or a pool supply store.
If you discover a sealant had been applied, you will need to diamond grind or vacuum shot blast the floor to remove any sealant. Diamond grinders are available at commercial rental companies.