When you are removing concrete sealers, paint, latex, enamel, epoxy, and polyurethanes from concrete there are three basic types of chemical strippers.
I'm not a big fan of the caustic strippers, but I do have recommendations for the biodegradable and solvent based ones.
Biodegradable strippers are made from natural plant material. They are much safer for you and the environment than other chemical strippers. The active ingredients found in biodegradable strippers are typically acids or esters derived from plants. Common plant sources include pine oil, corn sugars, citric acid and soy oil.
They usually take longer and may require more applications than some of the other chemical strippers but are easier to use, have less odor, are safer for the environment, and clean up & disposal of the by product is usually easier.
The best, 100% biodegradable, concrete cleaner - paint stripper- adhesive remover that I have used is Novion Universal Concrete Cleaner.
This cleaner/stripper is non-toxic, non-corrosive, and non-hazardous to you, your pets, and your plants.
Solvent based strippers are the most common types of strippers used when removing concrete sealers. They work fast and you don't have to use as much material as other strippers.
Look for ones that contain the chemical Methylene-chloride. This is the most popular and will remove most all sealers from concrete.
Other types of solvent strippers include N-methylpyrrolidone (NMP), dibasic esters (DBEs) and combinations of acetone, alcohol and toluene.
Solvent strippers only work if you keep the surface wet, don't let the stripper dry out or evaporate, you may have to re-wet the surface a couple times in 20 or 30 minutes before you can remove the sealer.
Most solvent based strippers are aggressive enough to remove almost all types of coatings and sealers from concrete.
Common resins used in sealers like acrylic, epoxy, polyurethane, polyaspartic and polyurea are no match for a good solvent based chemical concrete stripper.
For safety: Keep in mind solvent based strippers are very flammable. They can cause severe skin irritation breathing the fumes over long periods of time could cause liver problems. Always wear a mask and make sure there is good ventilation.
The solvent based stripper I use to remove paint and sealers from concrete is Lightning Strip. It penetrates through the paint/sealer and bubbles it off for easy removal, far better than any other stripper I have used.
Caustic chemical strippers are made from powerful alkaline chemicals. The high pH of the alkaline causes the break down of the sealer, allowing for easy removal from the surface of the concrete.
Caustic strippers are a good for removing latex, alkyds or enamel paints from concrete.
They are not a good choice for removing acrylic concrete sealer, epoxy, polyurethane, or polyaspartic coatings because these coatings have good chemical resistance to caustic chemicals.
The temperature should be above 50 degrees and plan on applying many times to completely remove the coating.
One advantage to using a caustic stripper is it's less harmful and easier to handle than solvent-based strippers.
Once the stripper has done its job, a neutralizing wash is required to remove the coating and any remaining stripper to prepare the concrete for the next process.
Make sure to dispose of the waste material properly, as caustic strippers tend to stay active and can react with other chemicals even after they are removed from the concrete.
NEW FOR REMOVING CONCRETE SEALERS: Deco-Strip from Nox Crete is a biodegradable concrete coating stripper designed to remove old, worn out acrylic sealers and coatings from decorative concrete.
Deco-Strip combines a blend of strong, yet bidegradable and environmentally safe solvents and surfactants, designed to quickly penetrate and soften decorative concrete acrylic sealers and coatings allowing for their complete removal.
This stripper will return decorative concrete back to its original unsealed condition allowing for the reapplication of a new coat of sealer.