The Concrete Network

Caustic strippers

How they work. Caustic strippers are made from strong alkaline chemicals. The high pH of the alkaline causes the destruction of the coating film, allowing easy removal from the substrate.

When to use them. Caustic strippers are a good option when removing latex, alkyds or enamel paints from concrete. They are not a good choice for removing acrylic, epoxy or polyurethane coatings because these resins have good resistance to caustic chemicals. A caustic stripper also doesn't work well when temperatures are below 50F, and thicker-build coatings will require many applications, more so than with other types of chemical strippers.

Safety precautions. An advantage of caustic strippers is that they are generally 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.

Solvent-based strippers

How they work. Solvent-based strippers are by far the most common type of stripper used today. The reason they are so popular is because they work fast, and a small amount of stripper goes a long way. Methylene-chloride based strippers are very popular, and work very well on all resin types and thicknesses. Other types of solvent strippers include N-methylpyrrolidone (NMP), dibasic esters (DBEs) and combinations of toluene, acetone and alcohol. Solvent-based strippers only work when they are wet, so taking steps to slow the evaporation of the solvent is important for product performance. Once the coating residue and any remaining stripper have been removed, cleanup consists of scrubbing with soap and water followed by rinsing with clean water. Using a high-pressure washer is recommended.

When to use them.Most professional applicators like to use solvent-based strippers because they are fast, aggressive and will remove almost all types of coatings or sealers in one or two applications. The common sealer resins used on concrete (acrylic, epoxy, polyurethane, polyaspartic and polyurea) are no match for a good solvent-based chemical stripper. However, these products are more effective when used in cool, draft-free conditions because heat and wind tend to cause rapid solvent evaporation and slow or stop the stripping process.

Safety precautions. Extreme caution should be used when working with methylene-chloride-based strippers, as they can cause severe skin irritation and permanent liver damage if used excessively. The other types of solvent strippers are less harmful to work with, but tend to evaporate quickly and can be highly flammable. Good ventilation is always important when using solvent-based strippers, so open windows and doors, and keep fans running to circulate the air.

Biochemical strippers

How they work. Biochemical strippers are the newest category of stripper, growing steadily in popularity and availability over the last five years. Their popularity stems from their sustainability (they are made from natural plant material) and low environmental impact (they contain no solvents or harsh caustic chemicals). The active ingredients found in biochemical strippers are typically acids or esters derived from plants. Common plant sources include pine oil, corn sugars, citric acid and soy oil.

When to use them.I have found that most professional installers will only use biochemical strippers if the work being done is in an environmentally sensitive area where solvent odors, stripper overspray or rinse water could potentially kill grass, plants or trees. Biochemical strippers are the easiest of the stripper categories to work with, have the least offensive odor, and are often considered to be eco-friendly. However, they are the least aggressive type of stripper and need to remain on the surface for long periods of time to get the job done. Coating thickness also has a major effect on the amount of stripper needed and how long it needs to stay on the surface. I have seen it take 12 to 24 hours for a biochemical stripper to remove a thick-build epoxy from a concrete floor.

Safety precautions. Most biochemical strippers do contain N-methylpyrrolidone (NMP), which can cause minor skin irritation.

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