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Scott paint solutions:
unlike stucco, precast units such as lintels, window sills and tilt slab walls are of a much higher density than stucco and typically are extremely smooth and can contain surface contaminants related to form release agents, lubricants, grease, etc. The key to successful painting of precast cement is surface preparation. Just because the surface feels dry does not mean it is ready for paint. To increase chances for success, do the following:
1. Pressure wash the surface with clean water at no less than 2500 psi. If the surface feels greasy or gummy, utilize a commercial degreasing agent prior to pressure washing.
2. Areas of whitish efflorescence deposits exuding from the surface should be scrubbed with a solution of 10% muriatic acid and water, and then rinsed and allowed to dry.
3. After cleaning, check the surface over. Areas of a hard glaze, producing extreme slickness, may require sand blasting before paint can properly adhere.
4. MOST IMPORTANT! - Apply one coat Scott Aquaseal Latex Surface Conditioner White #692 to all prepared surfaces and let dry.
Due to the density of precast panels, it can take a much longer period of time for trapped moisture to exude out, which sometimes causes late-appearing efflorescence. The paint does not cause that effect. Scrubbing with the muriatic acid solution and touching up will repair the situation.
A good test to make sure the surface is dry is to tape down a 2’x2’ piece of clear plastic and check for condensation after 12-24 hours. If there is condensation under the plastic, the concrete is not dry enough to paint.
WARNING: Without priming with a high adhesion primer such as Scott Aquaseal, avoiding spot peeling on tilt slab construction cannot be guaranteed.
