Causes:
Concrete floors present numerous potential adhesion
problems for coatings. Concrete is a highly alkaline
material that reacts chemically with oil or alkyd-based
finishes to weaken their adhesive bond. Concrete also
transmits moisture, bringing soluble salts to the surface
(efflorescence) and creating a sandy or dust-like
condition at the surface.
In addition, grade level or sub-surface floors are subject
to moisture penetration. Moisture and poor surface
preparation are the primary causes for peeling from
concrete floors. Other possible causes include hard-troweled
concrete, which presents a physical barrier to adhesion by
not permitting penetration of coatings. Older concrete can
become crumbly, and accumulations of grease or oil create
a barrier limiting adhesion.
Solution:
Remove paint by scraping and sanding.
Clean floor by scrubbing with hot water and a strong
detergent solution. Avoid mild dishwashing detergents.
If this fails to remove the paint, it may be necessary to
use chemical stripper. Follow the directions carefully.
Floors that have been subjected to long term oil and
grease must be aggressively scrubbed with a grease
dissolving compound, such as Benjamin Moore® M83
Industrial Maintenance Oil and Grease Emulsifier. Follow
the label directions carefully.
In all cases, rinse the floor thoroughly. Allow the
surface to dry for several days.
The next step, called etching, requires protective
goggles, boots and rubber gloves to be worn during the
process. Mop on a 10%-solution of muriatic acid and water
on the clean floor. Allow the solution to remain on
surface until bubbling ceases (10 to 15 minutes). Flush
surface with water and dry completely.
When floor is properly etched, it should resemble texture
of fine sandpaper. Etching neutralizes the alkaline
surface and provides a better bond. It also helps remove
salt deposits (called laitance) that can occur on concrete
surfaces.
Sand off any crumbly areas of loose concrete. The floor
should now be ready to paint. |
