Paint With Confidence

Exterior Common Issues & Solutions

Poor Alkali Resistance

Text & image courtesy of the Rohm & Haas Paint Quality Institute

Poor Alkali Resistance

Color loss and overall deterioration of paint film on fresh masonry.

Possible Cause

Oil-based paint or vinyl acrylic latex paint was 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, the painter should apply a quality, alkali-resistant sealer or latex primer, followed by a top quality 100% acrylic latex exterior paint. The acrylic binder in these paints resists alkali attack.