We have had poor experience with applying high-gloss enamel paints over concrete surfaces. The paint eventually seems to flake off regardless of paint quality or the primer used. Is there any way of overcoming this?
The flaking is due to alkalis in the portland cement which attack the oil or synthetic-resin paint vehicle. In general the earlier the paint is applied after the concrete is cast, the sooner it will flake off or disintegrate. For this reason ordinary commercial paints are rarely suitable for use on concrete. If possible it is suggested that a cement base paint be used to obtain the color and the gloss provided by means of a silicone or other synthetic resin top coat. A treatment that has also proved effective is to brush down the surface thoroughly with a solution of 4 pounds of zinc sulfate to a gallon of water, letting it dry before painting. Such a treatment should be effective for at least a year, and usually considerably longer, depending on the aggressiveness of the cement and the sensitivity of the paint.