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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!

PEELING FROM WOODEN WINDOW SILLS AND  FRAMES

Paint usually peels from window sills and frames because of condensation. Water standing on the sills eventually penetrates the paint film. When it evaporates, the pressure under the film causes peeling.

Solution

Remove all the paint by scraping, sanding, and, if necessary, using a chemical stripper. The use of a heat gun is a good alternative to chemical strippers. Either method can damage unprotected glass or window sealing material. Caulk where necessary, especially at every 90° angle and crevice, to eliminate any opportunity for moisture to penetrate into the wood substrate. Coat the sill with an exterior primer and finish coat. When painting frames, leave a 1/16-inch edge of paint on the pane to prevent water from getting behind the film. Open vent holes in aluminum window trim.

Other solutions involve using cedar wood as a replacement for pine, which soaks up water like a sponge. Paint the butt ends of the wood before replacing the sills.

Use oil-based gloss paints for surfaces exposed to standing snow and rain to help keep water from entering the wood. On new wood, use two topcoats of oil-based gloss. (Check safety and environmental regulations and codes.) Some manufacturers have latex primers that are impervious to water. The use of storm windows and dehumidifiers also helps to prevent peeling.

Article prepared by Rick Anderson of Vancouver’s Best Painters.

  PEELING FROM GLAZED WESTERN RED CEDAR OR REDWOOD SIDING

Mill-glaze is a hard, varnish-like glaze that appears on smooth, flat-grained Western Red Cedar and occasionally on redwood.

There is controversy over the exact cause of mill-glaze, but the general belief is that it is caused by planing and/or drying the lumber. During the milling or planing process, overheating of the flat-grained, smooth siding may bring water soluble resins to the surface, creating a hard, varnish-like glaze. Mill-glaze problems normally occur when siding has been installed smooth side out.

Solution

If the surface is unpainted, the best system is one that uses three coats, consisting of one coat of primer and two coats of latex finish. The most important feature of the system is the primer. It must be one that seals in tannic acid and prevents extractive bleeding. If, after one coat of primer dries, a brownish stain forms on the surface, an additional coat of primer must be applied to seal in the stains in the affected areas. Allow the first primer coat to dry before re-priming. If no additional stains are present, apply two coats of a high-quality latex finish.

For repainting over mill-glaze problem areas, remove the coatings either by pressure washing or hand scraping. Apply primer as indicated above and finish with two coats of latex finish.

Newly-installed siding should be finished as quickly as possible. Ultraviolet rays from the sun tend to degrade the integrity of the wood’s surface. A 50% loss in adhesion occurs on Western Red Cedar weathered for 16 weeks prior to finishing.

Abrading the mill-glaze surface by sanding prior to painting will ease surface tension and provide a better surface for the initial primer coat.

This article prepared by Rick Anderson of www.vancouversbestpainters.com call: 604-PAINTER

Paint Problem:  Painting Peeling From Brick

The most common cause of peeling from surfaces composed of mortar, brick, building block or concrete is efflorescence. Soluble salts are contained in these materials. When dissolved by water, they will be carried to the surface and will remain there after the water has evaporated. These crystallized salts push the paint away from the surface and peeling results.

Sometimes efflorescence occurs on brick walls of new construction. In the past, it was a common building practice to wash new brick or concrete walls with muriatic acid to clean away excess mortar. The acid was then washed away along with any chloride salts which may have formed. However, if the final rinsing was not thorough and the wall was painted later, any salts left on the bricks absorbed the moisture swell, causing peeling. (Current thinking is that acid etching, especially with muriatic acid, actually adds chloride salts back into concrete, so it is best to avoid it.)

Not all peeling from masonry is caused by efflorescence. Peeling can occur when an alkyd or oil-based paint is applied over a surface with a high alkalinity content (for example, unetched concrete). Alkyd resins that come in contact with an alkaline surface react by forming a soap film between the concrete surface and the alkyd coating. This reaction (saponification) results in extremely poor adhesion by the alkyd coating.

Solution

If efflorescence is evident, it must be removed before repainting. First, remove all flaking or chalking paint from the damaged area by wire brushing, sandblasting, or high-pressure water washing.Fill all cracks with a masonry patching compound, latex concrete patch, or caulking compound. If the surface is very porous, apply an alkali-resistant primer or block filler. Cover with latex house paint. If an exterior latex masonry paint is used as the topcoat, priming is not necessary.

To prevent recurrence of efflorescence on interior walls, the exterior walls should be sealed with a high-quality masonry coating. Waterproof coatings help seal exterior masonry walls.

Note: Extraneous water sources must be removed before painting (e.g.,

water migration at ground level, which is often caused by poor drainage).

Chalky or crumbly masonry surfaces can be primed with clear phenolic coatings (e.g., silicone sealer) to bond and seal old masonry.

This article was prepared by: Vancouver’s Best Painters:  Painters painting in the Vancouver and greater Vancouver area:  call: 604-PAINTER