Burning / Poor Alkali Resistance
 

Description:
Color loss and overall deterioration of paint film on fresh masonry, concrete or stucco.

Possible Cause:
• Stucco and mortar joints contain hydrated or "hot" lime, a dry compound added to improve the workability of these materials. Different mortars are compounded with different amounts of "hot" lime, depending on the end use of the mortar. This pro b l e m is then made worse by more "hot" lime being added at the job site.

• The alkalinity of fresh or new mortar, cement mixes and concrete is expressed numerically by pH readings. The pH of fresh cementitious materials is 13 to 14. It takes approximately 30 days for fresh cement materials to drop to an approximate pH of 9. A pH of 9 is less alkaline than a pH of 13, and a coating has a greater assurance of success when applied to a less alkaline surface.

• Once these cement walls are cured, the introduction of moisture into these walls will reactivate the high pH alkalinity, resulting in efflorescence, blistering and peeling of the paint film.

Solution:
• When damp areas are found on surfaces, the source of moisture intrusion must be repaired. The surface should be prepared by removing chalk, efflorescence and damaged paint film, and must be thoroughly dry before applying new paint.

• Both new and aged unpainted walls must be clean and free of moisture and efflorescence. (See EFFLORESCENCE for description and resolution).

• Paint products must be chosen with care.

Recommended System:
Primer
1 Coat of FLEX BON #194 Series Exterior 100% Acrylic Latex Primer
Topcoat
2 Coats of Top Quality FLEX BON Exterior Latex Paint