Poor alkali resistance

Possible cause

Poor alkali resistance occurs when solvent-based coatings are applied to new masonry that has not cured for a full year. Fresh masonry is likely to contain lime, which is very alkaline. Until the lime has a chance to react with carbon dioxide from the air, the alkalinity of the masonry remains so high that it can attack the integrity of the paint film.

Solution

Allow masonry surfaces to cure for at least 30 days, and ideally for a full year, before painting.

If this is not possible, apply a quality, alkali-resistant sealer or water-based primer, followed by a top quality 100% acrylic exterior paint. The acrylic binder in these paints resists alkali attack. Dulux recommends the Dulux Weathershield® range for use on exterior surfaces.