Mechanical grinding involves removing the smooth top layer to expose the raw concrete beneath. An industrial grinder equipped with diamond grinding blocks or a hand grinder using diamond discs is typically used for mechanically grinding the floor surface. Grinding makes controlling the surface profile easier, and it also helps to ensure a consistent result for the necessary texture to be achieved.
Depending on the requirement of the manufacturer for the coating, a concrete profile similar to 60 to 120 grit sandpaper is needed to ensure proper bonding. Grinding can leave uneven areas and gouge marks on the floor if it is not done properly. You should hire a professional floor coating company for a consistent and well-profiled surface.
Acid etching involves the application of acid to remove the top surface of the concrete floor. This method is good enough to prepare the floor for the application of protective coating especially if you are thinking of a DIY project or new concrete. Acid etching can expose the pores of the concrete under ideal circumstances but it won’t remove glues, caulks, mastics, and other common stains. If your floor is stained by any of these substances, you will need to clean the floor first to remove them.
The etching process can leave behind a wet concrete dust film that might clog the concrete pores if not fully cleaned off; this can lead to coating failure. Additionally, if the acid is not properly disposed of it can damage paving stones, landscapes, grass, etc.
Which One is Better?
Acid etching a garage floor is a great solution for those who are installing the floor themselves and do not have access to industrial grinders. However, for larger commercial jobs, older concrete, or worn floors we always recommend grinding before epoxy installation. This is because there are different concrete types with varying composition, texture, and hardness levels. This means there is not a one size fits all solution.
Diamond grinders use several grinding heads designed for the variations in concrete surfaces to ensure you get a proper surface profile that lasts a lifetime. Acid etching is a better option than power washing but it doesn’t give the same results as grinding.
Anyone with a decent commercial floor paint product and a little DIY skill can coat a garage floor and get a great end result. The concrete floor will fail if the coating doesn’t bond mechanically to the concrete floor, so the preparation is the most important part before applying any type of epoxy! So it is important that there is a solid bond between the concrete and epoxy coating so as not to end up with a failed epoxy garage floor.