Surface prep is the most important step of any coating project. An improperly prepped floor will result in either a failure, or shortened performance life of the floor covering. New or old concrete MUST be prepped before coating. There are two recommended methods for preparing your concrete floor for coating, the acid etching method, the mechanical method, or with a Flash Bonding Primer.
Acid Etching: A good, low cost, way to prep your floors. Acid etching removes any surface lime, which all concrete has, and creates millions of microscopic pores in the surface for effective adhesion. Acid etching is a safe alternative to using muriatic acid etch which can cause skin irritation and adverse reaction on certain people. There are several products on the market specifically designed for etching prep or you can use locally sourced muriatic acid.
Muriatic Acid: Normal mix is 4 parts water to 1 part acid, but you can use less water if your floor is sealed or extremely dirty. Always rinse well with water to neutralize all the acid afterwards. A solution of water and TSP (trisodium phosphate), available at most paint or hardware stores, is also an effective way to neutralize the acid. Regardless, allow plenty of time to fully dry before coating with epoxy (normally overnight works, but it can take longer under wet conditions).
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A test can be conducted to determine if the concrete moisture content is controlled to acceptable levels; this can be done by placing a 4’X4’ plastic sheet on the substrate and taping down the edges. If after 24 hours, the substrate is still dry below the plastic sheet, then the substrate is generally considered suitable for coatings. The plastic sheet testing is also a good method to determine if any hydrostatic pressure problems exist that could cause a bonding failure later.
Mechanical method: This method requires one of the following; a rotary type sander, a diamond grinder, or the use of a shot blasting machine to prepare the floor. These types of tools are available at most tool rental places.
Rotary Sander: You’ll need to source Diamond Floor Buffer Pads made for concrete if not available from rental location. These are special plates that affix to standard floor buffers and have diamond floating pads and come in versions for prepping concrete, stripping paint, or removing old adhesive from the floor.
Grinding: Surface Grinding works well on more even surfaces and help smooth out uneven floors. You can rent a diamond head floor grinder or ‘shot blaster’ at local tool rental stores. These methods work well for removal of old paint and sealers and ‘open up’ the surface very well for adhesion. Make sure to vacuum very well to remove any remaining dust. Please note that mechanical type surface prep can make your floors more porous, and necessitate the need for an additional primer coat. Test after prep assure a satisfactory result.
Shot Blasting: Shot blasting works better on rough, uneven and corroded/disintegrating concrete in need of repair. Shot blasting is normally sub-contracted out to professional companies that have the equipment.
Make sure to vacuum well after sanding or grinding, the process creates a lot of dust.
Flash Bond Primer: Some floors are not candidates for mechanical or acid etching due to installed equipment, restrictions regarding the creation of dust, etc.
For those circumstances there is a special primer called Flash Bond that allows the epoxy to stick to virtually any surface, including non-porous and sealed surfaces. This is a 1-part product that rolls on fast and easy. Often the cost of this special primer is equal to using mechanical means to prep.
After surface preparation and before application, repair all bug holes and grind down any projections. Repair all cracks or concrete imperfections.