I have been struggling with this project for a month. I have a covered patio with concrete floor. I was dreaming of acid staining the concrete in various patterns. Well, when I got to this task, I discovered lots of places with semi- peeling paint-I do not know what kind of paint. I have tried strong paint remover and epoxy paint remover, but at no avail. The only resolution which worked so far was using a 4 1/2 inch angle grinder with diamond blade. However, this was not a real solution as the grinder creates lot of dust and also gunk when is done wet. Also, 500 sq. ft patio with a little grinder??? Any suggestions please? Thank you very very much!!!