Replies

1. 
   wane | Jan 12, 2010 01:20pm | #1

   white powder is efflorescence, efflorescence are actually salts disolved in moisture and left behind when that moisture evaporates, waterproof the foundation from the outside and this will stop.

1. 
   benko | Jan 12, 2010 09:37pm | #2

   Maybe I should clarify a little. The problem came from a hot water leak. My question is what can I use to repair and clean the wall so that it will hold paint. I just know paint won't hold without getting it cleaned up well.

1. 
   DanH | Jan 12, 2010 09:57pm | #3

   Generally an acid wash will remove the crud. (How strong of acid to use is up to you.)

2. 
   brucet9 | Jan 12, 2010 10:05pm | #4

   Scrub the area with mild acid; muriatic is good, so is phosphoric and even ordinary white vinegar will work. The acid dissolves those built-up salts and also etches the surface of the concrete a little.

   You need to lightly rinse the surface afterward to remove the dissolved salts and any excess acid that remains. Let the area dry thoroughly before painting. If the concrete is still wet internally, further signs of efflorescence will appear and you'll have to acid treat it again.

   You probably know already that alkyd paint is not good over concrete or stucco because the resin breaks down from the alkali in the cement. Latex paints are ok for ordinary purposes and epoxies are best for floors or other areas subject to abrasion or heavy scrubbing.