Peeling From Concrete: Vancouver’s Best Painters: Call 604-PAINTER

PEELNG FROM. CONCRETE FLOORS

Hardeners added to concrete will often prevent good adhesion. Also, concrete contains alkali, which is drawn to the surface by water and deposited there. When the water evaporates the alkali leave a crystallized substance (efflorescence), which pushes against the paint film and causes peeling

An additional problem with concrete is that grease, oil, wax, and dirt tend to soak in and are difficult to remove. If they are present when the floor is being painted, they can cause peeling.

Moisture seeping through concrete floors in basements contributes to peeling paint. Floors that are laid on-grade, without a moisture barrier, do not hold paint well.

If a concrete floor is old, it could crumble, bringing the paint film with it.

Finally, peeling from concrete can also occur when an alkyd or oil base floor finish is applied to a bare, unetched, uncured floor. When alkyd resins in the floor coating come in contact with the alkaline concrete surface, they combine, react with one another, and form a film between the concrete surface and the alkyd coating. This reaction (saponification) results in extremely poor adhesion and softness of the alkyd coating.

Solution

First, remove the paint by scraping. If necessary, use chemical strippers. To clean the floor. scrub with hot water and a strong detergent solution. Avoid mild dishwashing detergents; they contain skin softening ingredients which interfere with paint adhesion. Rinse thoroughly. Allow the surface to dry for several days. Stubborn grease may continue to rise to the surface; in that case, you may have to scrub again.

Once the floor is clean, mop on a 10% solution of muriatic acid and water. Always mix the acid into the water, not the water into the acid. When painting with a water-thinned coating, use a 10% solution of phosphoric acid instead of muriatic acid. Allow the solution to remain on the surface for 10 to 15 minutes until all bubbling stops. Flush the surface with clean water and allow it to dry completely.

 Note: Local codes may prohibit flushing this material down a drain. If so,

it will be necessary to plug the drains and vacuum up the fluid.

It is advisable to wear protective goggles, boots, and rubber gloves during this process, which is called etching.

When the floor is properly etched, it should resemble the texture of fine sandpaper. Etching creates the necessary surface profile to provide a good bond. Make sure all acid is removed prior to coating. It might help to apply an alkali-resistant primer before repainting.

If the concrete is loose, sand off any crumbly areas, then repaint.  Latex floor enamels may adhere successfully.

Acid etching with a 10% solution of muriatic acid and water also halts saponification.  Follow the previously mentioned washing instructions.. Acid etching not only cleanses the surface of efflorescence, but also helps to remove latency in concrete.

If no vapor barrier is provided under a slab foundation, it may be possible to elmininate the problem by coating the surface with a breathing material such as concrete stain.  However, some surface cannot be successfully coated: long-term standing water is an indicator of such a surface.

Article Prepared by Rick Anderson of Vancouver’s Best Painters:  Call 604-PAINTER Today!