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Care and Cleaning of Anodized Aluminum

TODAY’S HIGH QUALITY ANODIZED ARCHITECTURAL FINISHES ARE EXTREMELY DURABLE. But even the best finish needs a little TLC, and with the most careful treatment of the windows, curtain-wall or storefront during installation and daily use, occasional damage will occur.

Maple Grove Public Works, Maple Grove, MN Photo courtesy of Dri-Design
Maple Grove Public Works, Maple Grove, MN   Photo courtesy of Dri-Design
GENERAL CONSIDERATIONS

As with any finished building material, aluminum requires reasonable care prior to and during installation and periodic cleaning and maintenance after installation. Although anodized aluminum is exceptionally resistant to corrosion, discoloration and wear, its natural beauty can be marred by harsh chemicals, abuse or neglect. Such conditions usually affect only the surface finish but do not reduce the service life of the aluminum. All exterior surfaces collect varying amounts of soil and dirt, depending on geographic area, environmental conditions, finish and location on the building. These factors and the owner’s attitude regarding surface appearance determine the type and frequency of cleaning required. The aluminum cleaning schedule should be integrated with other cleaning schedules for efficiency and economy. For example, both the glass and the aluminum curtain wall can be cleaned at the same time.
Cleaning may be required more often in one geographic area than another when appearance is of prime importance. More frequent cleaning will be required in heavy industrialized areas than in rural areas. Seasonal rainfall can affect washing frequency by removing water-soluble deposits and less adherent soil. In foggy coastal regions, frequent cycles of condensation and drying can create a heavy buildup of atmospheric salts and dirt, which may adhere resolutely. In climates where the rainfall is low, the opportunity for atmospheric washing of the surface is minimal.
In both wet and dry climates, recessed and sheltered areas usually become more heavily soiled because of the lack of rain-washing. More frequent and longer periods of condensation also occur in protected areas, increasing the adhesion of the soil. This is particularly true of soffit areas on overhangs, bottoms of facia panels, sheltered column covers and the like. Periodic maintenance inhibits long-term accumulation of soil, which, under certain conditions, can accelerate weathering of the finish.
Cleaning Procedures

 Cleaning procedures for aluminum should be initiated as soon as practical after completion of installation to remove construction soils and accumulated environmental soils and discolorations.

Cleaning work should start at the top of the building and proceed to the ground level in a continuous drop. Using a forceful water spray, an area the width of the stage or scaffolding should be rinsed as cleaning proceeds from the top down.

Because surface soils may be light or heavy, several progressively stronger cleaning procedures may be employed depending of the severity and tenacity of the soil. Only trial and simplest procedure to remove the soil is the one that should be used.

For light soils, the simplest procedure is to flush the surface with water using moderate pressure. If soil is still present after air-drying the surface, scrubbing with a brush or sponge and concurrent spraying with water should be tried. If soils still adhere, than a mild detergent cleaner should be used with brushing or sponging. Washing should be done with uniform pressure, first horizontally then vertically. Following the washing the surfaces must be thoroughly rinsed by spraying with clean water.

If it is necessary to remove oil, wax, polish, or other similar materials, MEK or an equivalent solvent is recommended for clean up. Extreme care must be exercised when solvents of this type are used since they may damage organic sealants, gaskets and finishes. These solvents should never be used on anodic finishes protected by clear organic coatings unless the organic coating has deteriorated and should be removed.

Removing heavy surface soils may require the use of an abrasive cleaning pad. In this procedure the pad is thoroughly soaked with clean water or a mild detergent cleaner and the metal surface is hand scrubbed with uniform pressure. Scrubbing action should be in the direction of the metal grain. Scrubbing with a nylon-cleaning pad impregnated with a surface protectant material is also recommended for removing stubborn soils and stains. After scrubbing, the surface should be rinsed thoroughly with clean water to remove all residue. 
In some circumstances it may be desirable to wipe the surface with a solvent. The surface is then permitted to air dry or is wiped dry with a chamois, squeegee or lint-free cloth.

Using power-cleaning tools may be necessary to remove unusually heavy soils from large areas including panels and column covers. When using such tools, the surface must be continually flushed with clean water or a mild detergent cleaning solution to provide lubrication and a medium for carrying away the dirt. After an area has been machine scrubbed, it must be rinsed with clean water and thoroughly scrubbed with a fairly stiff bristle brush. The surface may then be air dried or wiped dry.

Inspection
Care must be taken to see that metal seams, crevices, sills and other areas that can trap water, cleaner or dirt are carefully cleaned and dried. A final inspection, by a qualified representative is recommended, to ensure that no discoloration or stains remain on the surface.
Cleaning Precautions

Certain precautions must be taken when cleaning anodized aluminum surfaces. Aluminum finishes must first be identified to select the appropriate cleaning method.

  • Aggressive alkaline or acid cleaners must never be used.
  • Cleaning hot, sun-heated surfaces should be avoided since possible chemical reactions will be highly accelerated and cleaning non-uniformity could occur.
  • Strong organic solvents, while not affecting anodized aluminum, may extract stain-producing chemicals from sealants and may affect the function of the sealants.
  • Strong cleaners should not be used on window glass and other components where it is possible for the cleaner to come in contact with the aluminum.
  • Excessive abrasive rubbing should not be used since it could damage the finish.
On-Site Touch Up and Correcting More Severe Damage
It is almost a given that some damage will occur and touch-up work will be required during or after installation. But the good news is that both painted and anodized surface damage can be easily repaired if the damage is slight such as a scratch or rub mark. Minor painted surface damage can be sanded prior to touch-up painting with excellent results. Sanding of anodized material that is going to be touched up is not recommended. The anodized surface is aluminum oxide, which is generally harder than the sandpaper. Some rub marks on an anodized surface can be removed with a mild abrasive pad such as the Scotch-Brits pad prior to touch up painting.Touch-up paint is supplied in small aerosols or bottles with a built in brush for easy application and is to be applied very sparingly. It is intended to cover small blemishes or to touch-up exposed cut ends on fabricated parts. It is not intended for use on large areas of more than a few square inches. The color will closely match the factory applied painted or anodized finish, however the finish is not as hard nor performance the same as the baked on finishes. After cleaning the area to be touched up, wipe the area with denatured alcohol to remove any moisture or cleaning residue and apply the touch-up per the finisher’s instructions. Use caution as excessive use of touch up paint may void the original finisher’s warranty.
Poplar Creek Church photo4CORRECTING MORE SEVERE DAMAGE: (Calling in the Pros) At times a window, curtain-wall or storefront frame will become damaged or discolored beyond the point where simple field touch-up will correct the problem. Damage can result from a variety of sources including final cleaning of the building facade without proper protection of the aluminum surfaces, environmental impact from sea-coast or corrosive atmosphere exposure, long term neglect, or selection of the wrong finish at the time the material was finished and fabricated.
Linetec employs field service professionals who are trained in the proper preparation and application of field applied architectural finishes. Coatings that meet AAMA 2605 specifications and which can be field applied are available to these professionals. The highly specialized coatings, known as ADS Systems, can be tinted to match an anodized finish color.
Special cleaning and pretreatment procedures are critical to achieve the desired long-term results. The ADS paint must also be formulated to closely match the characteristics of the existing finish, particularly if only a portion of the existing surfaces will be refinished. Specifically, the new coating should be formulated to have approximately the same fade or chalk characteristics as any exposed original finish so that the entire project will have a uniform appearance for many years.Completion of a field repair can be handled in several ways, but in general, will begin with an initial contact with the field service professional to describe the problem. The scope of a field-refinishing project varies greatly, involving anything from a single door or window to a building elevation or an entire building. Usually, for all but the simplest repairs, the field service professional will recommend a site visit to examine the problem.
Following the site visit the field service professional will prepare a quotation for the work to be completed and also a sample color chip for approval. At times preparation of an on site sample for approval (a single door, panel or window) will be recommended. Following acceptance of the quotation and samples and preparation of a contract for the work to be completed, the work will begin. Field repairs can generally be performed at temperatures above 50 degrees Fahrenheit. The field service professional will handle all of the details such as permits, sidewalk protection and barricades.
Contracting for the services of a professional who specializes in the refinishing of architectural metals will assure that the work is completed using the correct methods and proper materials, assuring satisfaction with the long tern results guaranteed.
For addition information you can purchase the AAMA CW-10-12 Care and Handling of Architectural Aluminum from Shop to Site guide or AAMA 609 & 610-09 Cleaning and Maintenance Guide for Architecturally Finished Aluminum.