Floor Preparation for Concrete Coatings

Surface preparation is key to any surface to be coated.  Depending on the coating application, there may be several options to surface preparation.  Refer to manufacture’s recommendation.

Here are some options in preparing concrete for coatings:

Pressure Wash           Use a pressure washer capable of 3000psi of greater.  You are trying to remove surface dirt and contaminates to give the concrete a clean look prior to sealing.  Caution with the different tips and pressure.  You do not want to cut onto the concrete or streak it by focusing your pressure too close.  Practice before going for it.  Allow time to dry prior to coating/sealing (usually 24 hours at 75°F.  Remember protective gear (safety glasses and gloves) when power washing.

Acid Etch                    Effective and most economical method.  Using industrial grade muriatic acid, mix 3 parts water to one part muriatic acid.  Pour mixture onto surface area to be etched.  Using a push broom, scrub the area and keep wet for 10-15 minutes.  Neutralize the surface using a 10:1 mixture of water and ammonia or baking soda.  Apply to surface the same way by pouring the mixture over etched area and with a push broom gently scrub the concrete.  Do not let the acid of the neutralizing solution dry on the surface. If there is a drain in the floor, the spent acid (dirty water) can be rinsed down the drain.  If no drain exists, the water needs to be removed with a wetvac until only clean clear water is present.  Washing the spent acid solution out of say a garage on to dry concrete will stain the concrete.  To avoid staining, soak concrete with water prior to rinsing. 

The etched finished on the surface should resemble 100 grit sandpaper.  For most coatings, 24 hours of drying time is needed at 75°F before coatings can be applied.  Use safety protective gear when using this method (safety glasses, gloves, and splash apron) and use in well ventilated area or use the recommended respirator for acid

Diamond Grind           Very cost effective and faster job turn with less trips to the job.

The use of heavy diamond grinding equipment can grind old or new concrete, remove old epoxies or other coatings and prepare it for new coatings, stains or overlayments. The starting process for grinding concrete is depending on the concrete surface and final application of the concrete floor if it is a preparation for coatings or overlayments.

Rentals are available but if you are doing this for real, should be looking to invest in a good machine.  There are different grits available to achieve different surface profiles.

Shot Blasting              Shot blasting is a cost effective and environmentally friendly method for preparing concrete surfaces. This labor and time saving process strips, cleans and profiles simultaneously.  Shot blasting leaves the surface immediately ready for the application of coatings or overlays, eliminating drying time because water has not been introduced.  Shot blasting produces the highest bonding character of any surface preparation method.  Metal abrasive thrown by the rapidly rotating blast wheel is accelerated towards the surface being prepared. The media strikes the surface and rebounds, along with removed contaminants, into a recovery chamber or separator. Very little abrasive is lost and the usable media is returned to the storage hopper for recirculation by the blast wheel.  Different surface profiles can be achieved by varying shot size, shot flow rate and machine travel speed.  Remember to always wear eye and ear protection when shot blasting.

Sand Blasting              Long-sleeved clothing, boots, leather gloves, ear protection and a blast hood with air feed are necessary when sandblasting. 

Sandblasting can quickly remove most surface materials using compressed air and abrasive medias.  This is for exteriors and works best on irregular surfaces such as stamped concrete.  Masking off sections, abrasive clean-up and dust need to be considered before selecting sandblasting as an option.