Can I seal a painted garage floor?
No you can't seal over paint. If you want to apply an epoxy-based sealant then all the paint will have to be removed from the floor. There are good chemical paint strippers that you can use to remove the old paint. Contrary to what the post said, you will need to acid etch or grind the cement of your floor after you remove the paint. The reason of this is that epoxy based floor sealers need the pores of the concrete opened up and exposed in order for the epoxy to adhere properly. If you don't do this then it just peels up off the floor like your paint did. This does not hurt the finish of the concrete, it actually will make the epoxy last much longer.
That is a pretty tough one to be honest. I have done some work in this industry and every situation can be a little different depending upon the surface of the concrete you are working on. Smooth concrete with little or no aggregate is a little easier than a surface with clearly visible aggregate/rock. For stripping, start with a commercial grade grinder with a wire brush attached. Don't grind through the concrete but take the old paint off. Using a leaf blower blow all old paint, dust, debris, etc, off. Next, using old rags wipe the ENTIRE area that paint/sealant is to be applied with Xylene (an industrial strength solvent) that is HIGHLY FLAMMABLE. Wear gloves as Xylene can be absorbed through the skin and is toxic/carcinogenic. Use the heavy disposable type nitrile gloves as regular latex will deteriorate very quickly from the Xylene. Be certain concrete surface is CLEAN AND DRY. Apply and cure appropriate sealant/paint. There are countless varieties out there depending upon the surface, intended use, chemical and environmental exposure, etc. A word of warning and disclosure, most of the work I did was under the supervision of a foreman and we were fixing botched DIY jobs where average folks tried to seal, paint or surface garages, patios and decks. Often times the highest expense to the customer was the labor cost involved in removing what they tried to apply themselves. I would recommend getting a quote from a licensed contractor who works in the sealants and coating industry first. Make an educated decision from the potential cost of doing it yourself or paying someone who will do and stand by their work....If the paint/surface/sealant fails it will be their dime, not yours. I would go this route myself before doing my own garage and I have done this work in the past. Hope this helps and good luck!
They make some really good floor paints. If I were you I would clean any loose paint off the floor clean it real well with a solvent to remove any oils and then wash with a good detergent. Rinse really well to remove any residue. Then when you repaint it with a floor finish it will act as a sealer and look really good. To remove all the paint with sand blasting would probably hurt the finish on the concrete and not look very good. This is the process I would use. I have painted many garage floors. I worked in a complex with one hundred and sixteen units all with painted floors. Good luck