For the most part when flooring manufacturers or retailers tell you that "their floor is the best product out there and it will never peal up" they are only 'half' lying.
What they should be telling you is that the chemical makeup of their product will never fail. However, there are two key components of creating a rock solid garage floor, 1. the prep, & 2. the top coat (this should be a polyurethane or polyurea - not epoxy). Regardless of what product you end up using for your garage floor the preparation of the concrete is the foundation of getting a flooring product to adhere to the substrate. There are a number of ways to go about doing this, listed in order of preference:
1. [Diamond Grind] your Floor (you can either rent, buy or pay someone to do this) optimum finish grit is 150 or less. The reason diamond grinding is the best technique has to do with the finish quality and overall adhesion of your flooring product. The key to grinding is that the diamonds grind off any contaminates as well as break open the individual silica particles, leaving fresh, rough surfaces for the flooring material to mechanically bond onto. Another reason diamond grinding is top of the list is because as you run the large diamond head across your floor it also does some smoothing out of any rough spots or high points. In essence it is re-shaping your floor to a certain degree making it flatter and presumably a more desirable surface.
2. [Lead Shot Blast] - this technique takes thousands of tiny lead shot and shoots it out at your floor and tremendously high velocities. The machines that do this are much like a pressure washer except it only shoots straight down and then there are magnet trays to re-collect the shot and funnel back into the hopper to be re-shot. This technique is good and it will give your substrate a great profile but there are two major drawbacks to this method -one, is that if you are trying to remove oil or gunk off the floor it tends to drive it down deep into the pours of the concrete and not fully remove it. The second is that old concrete tends to degrade at different rates and different depths all dependant upon who originally mixed and poured the concrete. The concrete can begin to have slight variations in height much like if you sand blast a piece of wood (the hard grain doesn't get blasted away as easily as the soft wood so you end up with a very textured piece of wood). Now it's not as extreme when you are dealing with concrete but it is a possibility. All in all if you can't diamond grind - shot blast.
3. [Acid Etch] - you need to be careful using the acid etch products as well as conform to any state law that might prohibit certain products. In California it has been banned completely so check your local code before trying this process. For the most part Acid etch solvents are sold by several companies but very few are a true "Acid". Most of the time you need to go through safety training as well as have a wholesale account to get your hands on the most aggressive acids. Acid etch can work but the mix ratio has to be spot on and the amount of time it's used on the concrete needs to be timed out and washed off within the allotted time. If taken off to early you won't get good adhesion and if left on to long you will have a breakdown of your substrate that will never be repairable. The acid in many instances doesn't take off all the oils and contaminants that have built up over the years. Doing an acid etch of your concrete is much more of an art than a science to do it correctly. Much cheaper in the short run than the aforementioned methods but potentially much more costly in the long run.
4. [Off the Shelf Cleaners] - there are tons and tons of off the shelf degreasers and concrete cleaners out there that will help "clean" your concrete. This for the most part is what a majority of the Do-It-Yourself floor applicators use but unfortunately your floor will not last the test of time with this method. We grind up hundreds of floors that use this technique because you simply don't give your concrete the proper profile in which the base coats can mechanically bond onto. These are great for looks but don't do enough to the concrete to properly prep it for a long term adhesion by hybrid polymer floor applications.
If anyone has any questions or comments please feel free to shoot them our way and we would be happy to help solve your flooring needs. If you need flooring product and would like to do-it-yourself check out http://www.garageenvyshop.com/Epoxy_Garage_Flooring.aspx