A coating of urethane is more abrasion and chemical resistant than epoxy. So why not just use urethane and be done with it? The catch is urethane does not bond well with bare concrete and requires a primer coat of a different coating type.
Epoxy happens to be the ideal primer, making the combination of epoxy and urethane the best concrete garage floor coating. Epoxy goes down first because it bonds well with the concrete. Urethane goes on top and adheres to the epoxy.
As with any other coating, adequate floor preparation is the most critical part of the process.
Before you decide to tackle this project, I suggest reading through the steps below and then refer back to them once you get started.
Before you even purchase the products, be sure the floor is suitable for such coatings by doing a vapor test. Take a few small pieces of plastic sheeting, lay them on the concrete in separate areas, and tape down all sides making it air tight. Leave them for at least 24 hours. Check for moisture build up under the plastic. If it's dry then you're good to go. If moisture is present, then epoxy/urethane (non-breathable coatings) should not be applied. Hydrostatic pressure will cause the coating to bubble and peel away.
Thoroughly clean the floor with mild detergents or TSP. Address specific stains such as oil and grease with cleaners and degreasers. Use a scraper or small grinder to remove any paint drippings, drywall mud, caulk, etc.
*A floor grinder can take care of all this while creating an ideal floor profile*Step 3
Acid etch the floor by spraying diluted muriatic acid (8 parts water:1 part acid) or special etching solution. What this does is eat away some of the cement on the surface to open up pores. A porous surface allows for a better mechanical bond.Step 4
Neutralize with ammonia (8 parts water:1 part acid) or baking soda. This brings the pH back to neutral for a better chemical bond because nothing bonds well with an acidic surface. Rinse thoroughly to get rid of any residue left over from etching. Allow floor to dry completely (at least 24 hours).Step 5
Wipe the floor clean with mineral spirits or denatured alcohol. This removes any hard water deposits or dust that may inhibit bonding.
Mix and apply water based epoxy according to label instructions. Throw paint chips on wet epoxy if desired.Step 7
Application of urethane... timing is essential for this step. There is a "recoat window" that begins about 8-10 hours after the epoxy is applied and lasts roughly 10 hours. During this window the urethane can be applied without having to scuff the epoxy. Obviously you don't want to start when the epoxy is still tacky, but by waiting too long the epoxy will harden past the point that anything can bond well with it.
*If for some reason you wait longer than 20 hours, then you need to scuff the epoxy. Lightly sand the entire surface. Vacuum the dust and wipe it clean with mineral spirits or denatured alcohol before applying urethane.*
Important: When using solvent based urethane, protect yourself with a respirator, goggles, gloves, long sleeves and pants. Make sure there's adequate ventilation by opening doors and windows and use fans to keep air moving.
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