We want to paint the concrete capstones that top an outside wall. The problem is that the previous owners already painted them with green oil-based gloss paint. I tried sanding them down and painting with a matt black paint and it looked great for about 6 months. It is now peeling and has bogey green spots showing. Could someone please advise me on the correct preparation to allow the paint to key properly. Perhaps you could also suggest the type of paint that I should use.
Thank you so much for your help.
