To prep painted concrete for epoxy, you must first remove the existing paint or coating and then prepare the underlying concrete surface to meet the necessary requirements for epoxy adhesion. This preparation is critical because epoxy should only be applied on a clean, porous, and completely flat surface free of moisture, greasy residue, debris, holes, and cracks.
The process typically involves several key steps:
1. Remove the Existing Paint
The first and most crucial step is to remove all traces of the old paint or coating. Simply applying epoxy over existing paint is not recommended, as the epoxy will only be as strong as the bond of the old paint to the concrete.
Methods for paint removal often involve mechanical processes. Some effective techniques include:
- Diamond Grinding: This method uses specialized grinding machines with diamond abrasives to effectively grind away the paint and the top layer of concrete, simultaneously profiling the surface.
- Shot Blasting: This technique blasts the concrete surface with steel shot at high velocity, removing coatings and contaminants while creating an ideal profile for epoxy bonding.
While less aggressive and potentially insufficient for thick or well-bonded paint, acid etching is mentioned as a preparation method in the reference. However, it's generally more suitable for cleaning and lightly profiling bare concrete rather than removing paint.
2. Repair the Concrete
Once the paint is removed, inspect the concrete for any damage.
- Fill Holes and Cracks: Address any holes or cracks using appropriate concrete repair materials. Ensure these repairs cure properly according to the product manufacturer's instructions.
3. Clean the Surface Thoroughly
A clean surface is paramount for epoxy adhesion.
- Remove Debris: Sweep or vacuum up all dust, paint chips, and debris left over from the removal process.
- Degrease: Clean any greasy residue or stains using a suitable concrete degreaser. Rinse thoroughly.
4. Profile the Surface
After cleaning and repairs, the concrete surface needs to be profiled to create porosity and a texture that the epoxy can grip onto. This is where the methods mentioned in the reference come into play to make the surface more adhesive for epoxy resin.
- Mechanical Methods: Diamond grinding or shot blasting not only remove paint but also effectively profile the concrete surface, opening up pores and creating a rough texture ideal for bonding.
- Acid Etching: If the paint was removed by other means and the concrete is then thoroughly cleaned, acid etching can be used after ensuring the surface is bare concrete to create a porous profile. However, this requires neutralizing and rinsing the acid properly.
These processes remove unwanted irregularities from the entire floor and ensure the epoxy has a properly prepared substrate to bond with.
5. Ensure the Surface is Dry
Epoxy will not bond to a wet or damp surface. The concrete must be completely dry before epoxy application.
- Check for Moisture: Use a moisture meter or the plastic sheet test to verify that the concrete slab is dry enough for epoxy.
By following these steps, focusing on complete paint removal and proper surface preparation using methods like grinding, blasting, or etching as mentioned in the reference, you can create the necessary clean, porous, and flat base required for a successful epoxy application.
