When it comes to preparing a concrete garage floor for epoxy coatings or other garage floor coatings, there are two methods to consider; grinding and acid etch. This topic often spurs several questions such as “Which method is better?”, “Why do some companies grind the concrete before coating?” or “Won’t an acid etch work just as well as grinding the concrete floor?” Instead of jumping straight to the answers, let’s look at some of the how’s and why’s of grinding vs acid etching.
Just about anyone with a little DIY skill and a decent floor coating product can come in and coat a garage floor and get reasonably nice results. The big question is what will it look like in 3 months, 6 months, or a year? If the floor coating does not mechanically bond to the concrete floor, it WILL fail. The only question is how long before it does fail. There MUST be a good, solid bond between the epoxy coating and the concrete. Anything short of that will result in a failed epoxy floor coating that is flaking up, giving you an uglier floor than before you coated it.
To keep from investing good time and money into a floor coating that fails, make sure you first focus on the proper preparation. The problem with concrete for most all garage floors is that it is finished in a way that creates a very smooth surface. This seems like a good thing, but that smooth finishing reduces the porosity of the concrete, leaving little chance for the epoxy coating to bond. It is like painting a piece of glass, it will never “stick”. This means that the concrete floor needs to be profiled to open up the pores, allowing the epoxy coating to mechanically bond. This is where the grinding or acid etching comes in.
Without question, the best method of preparing, or profiling, a concrete garage floor for an epoxy coating or other garage floor coating is to grind the concrete. This is typically done with an industrial grinder equipped with diamond grinding blocks, but can also be accomplished with a hand grinder using diamond discs. By grinding the floor, it is much easier to control the surface profile and ensure a consistent result, providing the necessary texture. Depending on the manufacturer’s requirements for the coating, the concrete needs a profile similar to a 60 to 120 grit sandpaper to ensure proper bonding.
With an acid etch, it is very difficult to control and get any kind of consistency across the garage floor, leaving potential points for failure. If you are going to acid etch, the floor must first be cleaned, removing oils, paints, stains etc., adding an additional step to the process. If the acid is not diluted correctly, it can damage your concrete floor. The etching process leaves behind a wet concrete dust film that, if not fully cleaned off, will clog the pores of the concrete leading to a coating failure. On top of all of that, there is the proper disposal of the acid wash which can damage landscape, paving stones, grass, etc. About the only upside to acid etching is that it is inexpensive and a more available option for the DIY’er.
If you are going to hire a garage floor coating company make sure they mechanically grind the garage floor. If a floor coating contractor uses an acid etch in place of mechanical grinding, it is to cut corners and their dedication to quality is suspect. They may offer you a lower price, but the more expensive floor is the one you have to replace. Garage floor coating contractors that stand behind their work will always grind the concrete floor to ensure the proper bond.