Painting - Painting block wall with alkaline deposits?

I have a concrete block retaining wall around my house. They are about five feet tall and hold back a large hill behind. They are painted, but there is a white deposit that quickly bleeds through the paint. Sometimes it takes only a few days. It appears to be an alkaline deposit. Is there any surface coating I could apply to stop the white deposits from bleeding through. Sealing the reverse side of the block wall is not feasible.
Ron Matson

The white deposit is efflorescence, which is deposited on the surface as water comes through the wall.

The proper way to eliminate the efflorescence is to eliminate the moisture. Unfortunately, you have ruled out any work behind the wall.

You can use a brush periodically to remove the dry powder. The problem started when the wall was painted in the first palce and the paint may even make it more visable.

Corrections are not as easy as putting on another coating.

The pressure produced by the crystal formation as the moisture evaporates creates tremendous pore pressure that will force an opening in the coatings. Adding another coat could even make things worse, creating a situation there thick coatings could become a vapor barrier and areas of the paint could be forced off (peel). If you have freezing weather, the coatings can retain water, which will freeze and spall the concrete.

One possibility would be to attach wire lath and two layers of building paper tp the wall, creating a small gap for drainage/ventilation and then stucco the wall.

I am trying to prepare my walls for Thoroseal. I used the Drylol etch (Sulfamic Acid) to clean and etch the walls, but there still remains a small trace of deposits on the interior basement walls. Do I need to hit it again? Should I have used muriatic acid - which because it's inside, I'm VERY reluctant to do?

Al

I am trying to prepare my walls for Thoroseal. I used the Drylol etch (Sulfamic Acid) to clean and etch the walls, but there still remains a small trace of deposits on the interior basement walls. Do I need to hit it again? Should I have used muriatic acid - which because it's inside, I'm VERY reluctant to do?

Al


H&C (owned by SW) makes a concrete etch that is much less caustic than muratic acid. I don't know if it will kill the efflorecence though.

Might try to contact your local SW and discuss with manager. They can talk to paint techs if unsure, and get back with you.

Good luck.

BTW I agree on not using Muratic acid inside. Nasty, nasty.
Plus, it will kill you if you don't wear a mask with an acid cartridge installed. Thats always one way to finish out your project! (and never need to start another)

Maybe SW is Sherwin Williams? Don't know about the other

SW is Sherwin Williams. SWP is Sherwin William Paints. H&C Concrete Etching Solution is one of the concrete solutions offered by H&C, division of SW that manufactures concrete stains and sealers.