One of the most popular questions we are asked is how to remove an acrylic concrete sealer that was previously used. In order to accurately answer this question you need to determine the type of sealer that was initially applied.
How to determine if concrete was sealed with a water based or solvent based sealer:
Pour a small amount of Xylene on an area that is still coated by sealer and allow the Xylene to sit for 20 seconds. Remove any excess. Touch the area and if it is tacky or sticky the surface was sealed with a solvent-based sealer. If the concrete is not tacky or sticky the concrete was sealed with a water based sealer.
Generally speaking, in most cases, a solvent based sealer can be applied to a surface previously sealed with a solvent based sealer; however, it cannot be applied over a surface previously sealed with a water-based product. If you previously applied a water based sealer and are now looking to seal with a solvent based sealer you need to remove the water based sealer since the solvents will eat or soften the existing water-based sealer, destroying both coatings. Water based sealers can be removed through chemical etching, aggressive pressure washing or mechanical scarification.
If you previously applied a solvent based acrylic sealer and are now looking to seal with a water based sealer you need to remove the solvent based sealer since the water based sealer will be unable to properly adhere to the solvent based sealer. Start by removing any visible peeling and flaking and use a solvent based stripper such as Xylene to remove the previous sealer. Pressure wash the surface and allow concrete to completely dry before applying a new water based sealer. Please note that if concrete was dyed or stained using Xylene can damage or change the color of the concrete.
If your concrete was sealed with a solvent based sealer and you are looking to reseal it with another solvent based sealer like Cryli-Tek 5505 you can reapply the new solvent based sealer directly to the concrete without needing to remove the old sealer. Try and remove any visible peeling and flaking before resealing.
If your concrete was sealed with a water based sealer and you want to remove it, you can use a product such as Aqua Mix's Sealer and Coating Remover. You can also try acid etching the concrete (followed by neutralizing) or you can mechanically scarify the concrete to remove the previous sealer.