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Ask the Expert Question-and-Answer Archive

by Ron Joseph

July, 2004

Painting Concrete Garage Floor - Efflorescence

Q. My garage floor is concrete. We painted it about ten years ago. We need to repaint but we have had what I assume is efflorescence. We have had it for years. When we painted the last time, about ten years ago, we washed the floor with muriatic acid dilluted with water. We washed it off and then painted it with a concrete paint. How do I get rid of this and can we repaint the floor? I have even tried putting some dilluted ammonia on the spots but the efflorescence still comes up in spots. Please help. No one can seem to answer my questions.

A. The garage floor will need a good cleaning prior to painting. Lets use a high pressure water spray and a heavy duty masonry cleaner to remove all dirt and contamination. An extra full strength application of cleaner applied to any oil or grease stains should be sufficient.

Let the area dry for a few days before applying the topcoat paint.

Be sure that the paint selection is compatible with the existing topcoating.

Best regards,
Tom Burke

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