GodsTrichome;1338480 said:LED my friend, here is some information on efflorescence, which is what is probably causing your paint to flake off.
Efflorescence is a crystaline deposit on surfaces of masonry, stucco or concrete. It is whitish in appear-ance, and is sometimes referred to as "whiskers". Efflorescence has been a problem for many years, and is a topic of much controversy. The formation of these salt deposits are not mysteries. They are, for the most part, water-soluble salts that come from many possible sources to mar and detract from an other-wise beautiful and serviceable structure. First of all, there must be water present to dissolve and trans-port the salts. Groundwater is often a source of efflorescence. For water to carry or move the salts to the surface there must be channels through which to move and migrate. The more dense the material, whether it be brick, stone, stucco or concrete, the more difficult for the water to transport salts to the surface. Conversely, the more porous the material, the greater the ease with which salts are transported and deposited. Salt-bearing water, on reaching the surface of a structure, air evaporates to deposit the salt. When humidity is low, the water may evaporate before reaching the surface of the structure, leaving the salt deposit beneath the surface, and unseen. When the humidity is high, water evaporation is slower allowing more opportunity for whisker growth.Since humidity has a definite effect on whether or not the salts appear, it can be assumed that efflores-cence is a seasonal problem. The intensity of efflorescence increases after rainy winter seasons, de-creases in spring, and by summer has practically disappeared. This cycle may repeat for months or years, but generally the intensity of the efflorescence decreases in all but very extreme cases, and by about the third year it should be practically eliminated.
Removal of Efflorescence
Several methods are suggested. One is to use water under pressure or one of a number of products available from stone dealers; another is muriatic acid with subse-quent flushing with water. Acid applied to brick masonry, without previous wetting, may cause "burning" or discoloration of the brick and may also eat into the mortar. The Handbook on Reinforced Grouted Brick Masonry Construction suggests the use of light sandblasting for removal of stubborn efflorescence (after many months). Allowing the surface to dry thoroughly and then using a stiff brush, prior to wash-ing with water, has helped prevent re-penetration of the surface by the salt.
Various methods have been used in attempts to remove efflorescence from masonry structures. It has been found that when efflorescence is caused by soluble alkali salts, the salts will dissolve in water applied to the structure and migrate back into it. These salts would then reappear on the surface as the structure redried. It was learned accordingly, that the best way to remove these soluble salts was to brush the surface thoroughly with a stiff brush. Water, however, has been satisfactory for removing efflorescence from the face of concrete structures, since concrete is fairly well saturated with water. In fact, efflorescence in the form of alkali salts will be washed from the surface of concrete structures, if exposed to rain, over some period of time. If the coating is largely calcium carbonate or calcium sulfate, it adheres rather strongly and is difficult to remove by brushing. The practice developed in this case for masonry surfaces, has been to saturate the structure as thoroughly as possible with water, and then wash with diluted muriatic acid, followed immediately with an alkaline wash, then washed with water. The acid recommended is five (5) parts hydrochloric to one hundred (100) parts water, or twenty (20) parts vinegar to one hundred (100) parts water. The alkaline wash recommended is diluted household ammonia.
Much care must be taken in applying acid to Portland cement products. The acid will attack, not only the calcium carbonate and calcium sulfate efflorescence, but also other calcium compounds to produce calcium salts such as calcium chloride. It is, therefore, very important to neutralize the acid before it can attack other compounds.
Sorry about hijacking your thread my friend, hope that this was a help. I deal with this stuff almost weekly in my line of work. After treatment, I recommend painting the walls with Dry-Loc, and then with a high quality white exterior paint, with microban and anti-mold agents, a good choice would be Behr Premium Plus Ultra, it is affordable anyways, and easy to get.
Stay green, God bless, and PEEEEEAAAAAACCCCCEEEEE!!!
