Solution for Loose Flaking Paint

Remove all loose, flaking paint from the damaged area until you reach the bare metal. It is a good idea to follow coating removal with an application of a metal conditioner such al. Lithoform®, Galvaprep®, or similar conversion coating. Apply a galvanized metal primer, preferably latex, and follow with two coats of an acrylic finish.

If you must paint galvanized metal that has not weathered for six months, remove surface oil with a solvent such as lacquer thinner and/or a detergent wash, then coat the surface with a latex galvanized-metal primer or a Portland cement-based galvanized metal primer. Once the primer has dried completely, apply the topcoat.

PEELING FROM HARDBOARD SIDING

Peeling from hardboard siding is usually due to moisture buildup inside a structure. In tightly-constructed houses, moisture escapes through the walls because there is no place else for it to go. In the summer heat, the water trapped inside the exterior paint film is vaporized, and the resultant pressure causes peeling.

 Solution

The source of moisture must be removed either by installing vents and/or repairing worn caulking; more detailed recommendations are covered later in this module.

Remove all loose paint and sand the edges smooth. Apply a primer to seal the board and cover with a topcoat after the primer is thoroughly dry.

Hardboard, which is reconstituted natural wood, is fabricated by reducing natural wood to fibers and then pressing the fibers together into panels. It can be either tempered or standard. Tempered board is denser and has a higher moisture resistance. Standard hardboard should not be used outdoors where it will be directly exposed to the weather.

Rick Anderson

www.vancouversbestpainters.com

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Galvanized metal is very alkaline when received from the mill. In most cases, it also has an oil on its surface that prevents atmospheric humidity from coming in contact with the surface. This oil normally disappears naturally during the first six months of weathering; however, it must be removed if the customer wishes to paint before then. The oil is removed by solvent wiping or detergent washing. The alkalinity is then neutralized by acid wiping the surface with phosphoric acid followed by fresh water rinsing.

Failure to properly prime galvanized metal is usually the cause of peeling. When galvanized metal is allowed to weather for six months, it will develop white rust. This is the appearance of a white haze which dulls the galvanizing after exposure to the elements. This white rust must be removed by washing with water and detergent, followed by a complete rinsing.

Galvanized metal is usually specially treated to remove chemicals deposited on the surface after the galvanizing bath. Otherwise, peeling may occur (Figure 7). Peeling may also occur when an alkyd or oil-based product is applied over a bare galvanized surface. A chemical reaction occurs between the zinc metal used in the galvanizing process and the alkyd resins in the coating. When this reaction (called saponification) occurs, a soap film forms between the galvanized metal and the alkyd or oil coating.

Rusting also can cause peeling. Check the backs of the paint chips for signs of rust. Rusting often occurs because of failure to paint immediately after cleaning the metal surface.

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Paint Failure by Rick Anderson (Vancouver’s Best Painters)

INTERCOAT  PEELING UNDER EAVES AND COVERED PORCHES (SCALING AND CORNFLAMNG)

Intercoat peeling often occurs under eaves, covered porches, and other protected areas. The loose paint scale resembles cornflakes, which is why it is sometimes referred to as cornflaking.

Protected or shaded areas on buildings are susceptible to condensation and salt deposits. Water-soluble chemicals in paint films contain salts which are pulled to the surface by moisture. When the moisture evaporates, the chemicals are left on the surface in crystalline powder form.  This formation of crystals is due to sulfur dioxide, which is produced in varying amounts by burning commercial fuels that are carried through the air. When the chemical comes into contact with water, an acid is formed which reacts with some of the pigments in paint and leaves crystalline powder deposits.

The powder is not noticeable on white paint. On colors, it resembles salt. This depositing also occurs on siding, but the salts are washed away by rain.

These chemical salts are hygroscopic; meaning they will absorb moisture through an existing coat of finish that is applied over them if they are not removed prior to painting. The result is that a year or so later, the salts draw moisture through the existing coating film and form a pressure on the back side of that film. Gradually, that pressure becomes greater than the adhesive strength of the coating film to the substrate, and it is forced off.

Salts attract moisture, even after new coats of paint are added to the surface. When freezing temperatures occur, any moisture lingering on the salt layer freezes and expands, forcing the topcoat of paint outward, thus causing intercoat peeling.

Scaling also can be evident in protected areas where gloss paints have been applied. Lack of weathering leaves these surfaces hard and shiny. A new coat of paint will not adhere properly to the slick surfaces without correct surface preparation.

Solution

Protected surfaces should be washed with detergent to remove dirt from the paint. They then should be rinsed with a strong stream of clean water to take off the salts.

When the surface is dry, remove all loose paint with a scraper or wire brush and sand these areas, along with any glossy surfaces. Apply one or two coats of latex- or oil-based house paint.

Rick Anderson

www.vancoversbestpainters.com

www.vancouverindustrialpainting.com

www.604painters.com

local: 604-PAINTER

Toll Free: 1-800-PRO-PAINTER

EXCESS CHALKING

by Rick Anderson Vancouver’s Best Painters

Chalking is the excess formulation of fine powder on the surface of a paint film.

Eventually, all paints chalk to some degree. Generally, alkyds chalk more quickly and to a greater degree than acrylic latex coatings. Chalking is a result of the breakdown of the coating binder because of its prolonged exposure to the ultraviolet rays of the sun.

Chalking is caused by failure to adequately prime and seal a porous surface, by over-thinning the paint prior to application, or by spreading the paint too thinly.

All oil paint will chalk to some degree as the result of exposure to sunlight. On most surfaces, especially white surfaces, moderate chalking is helpful because dirt is washed away with the chalk when it rains. In addition, chalking is a normal, desirable way for the paint film to wear away and provide a good surface for future repainting. However, a freely chalking type of paint should not be used above masonry or brick because the chalk wash down will leave an unattractive discoloration on these surfaces.

If you wipe your hand over a surface and the chalk dust covers your entire hand, you should think about repainting.

 Sollution

The chalk residue must first be removed. This is easily accomplished with the use of a pressure washer. If one is not available, use a stiff brush and mild detergent and spray the chalky surface with a strong stream from a garden hose. The detergent will act as a lubricant to easily remove residual dirt and chalk in addition to any other foreign contaminants. After the surface has dried thoroughly, rub your finger to check if some chalk residue remains. If so, a surface conditioner (oil or acrylic) should be used under the finish coat.

If chalk wash-down on brick has occurred, the stains can be removed from the brick by scrubbing with a stiff brush and detergent solution. Use a strong stream from a garden hose to rinse. If the brick is a slightly different color after it dries, it can be masked by rubbing a piece of brick over the area, or by painting the area with a brick-colored coating.

Rick Anderson,

www.vancouversbestpainters.com

www.vancouverindustrialpainting.com

www.604painters.com

local: 604-PAINTER

Toll Free: 1-800-PRO-PAINTER