Material Precautions

Anodized finishes provide outstanding surface properties including excellent resistance to abrasion, erosion, and ultraviolet light degradation. These finishes are highly durable, have an exceptionally long life expectancy, and require only minimum maintenance.

Some basic guidelines to consider when preparing metal for an anodize finish are:

Aluminum BilletConsistency in Aluminum. The easiest way to ensure consistency in aluminum parts is to work with one metal source/extruder per project.


No mixing. Mixed aluminum alloys or even tempers will not produce uniform results. For best results use 6063 alloys for extrusions and 5005 for sheet stock.

Bend and form before finishing. Anodic films are very hard. As a result most post-production bending will lead to the film “crazing,” which will give the appearance of a spider web. Crazing produces a series of small cracks in the finish.

Store properly. Store aluminum in a dry and controlled environment. Do not allow moisture to build-up between the pieces as this will cause severe corrosion, known as white rust, which will not be removed in the finishing process. This is important not just to the customer; the finisher should also ensure proper climate control where aluminum is stored.

Avoid adhesives. Tape or adhesive on the aluminum may leave a residue that may not be removed in the anodize process.

Agree on specification and expectations. In the architectural industry, the most recognized specification is AAMA-611. If specific parameters are required, it is important to furnish the finisher with the desired requirements to ensure the job is completed to the customer’s expectation.

Watch for welds. Welded parts will show a color difference on the weld versus the remainder of the part. The heat developed from the welding process can disturb the metallurgy on nearby metal and cause a localized discoloration after anodizing. Ensure the proper 5356 alloy welding wire is used, and the lowest heat possible.

Prevent solution entrapment. Proper drainage holes are essential for drainage of solution allowing entrapped gas to escape from the parts. Even the tightest of welded joints will cause anodize chemicals to weep out.

Talk racking. The finisher needs to know where parts can be racked. There are a variety of ways anodizers can rack parts, from welding material to spline bars, to a screw down bolt system. In any case, contact marks are visible on the aluminum. It is important to define what is acceptable and what is unacceptable with regard to exposed surfaces and rack marks.

Handle with care. Good shipping practices are essential to a quality job. Prior to shipment to the finisher, package metal carefully to ensure the metal arrives dry and free of scratches and dents.

Quality in, quality out. Metal free from defects will produce a higher quality finish. Avoid sending the finisher metal with scratches, dings, heavy die lines, die pick-up, etc. These metal quality defects will show through the anodize process.

Installation Concerns

To ensure a long-lasting anodize finish, the following issues should be considered during installation:

Construction imageDissimilar materials. Architectural designs often incorporate many different materials, making the potential for contact between dissimilar materials an important consideration. If questions occur regarding compatibility, the manufacturer of the aluminum products should be contacted.

Masonry work. The major source of damage to in-place aluminum components usually comes from the splashing, splattering, or run-down from adjacent or overhead masonry work. Acids used for cleaning operations also pose a serious problem. Any mortar, plaster, concrete, fireproofing, sprays, paints, or other wet preparations that inadvertently splash upon the aluminum must be immediately wiped clean before they dry and the affected area washed liberally with water. Dried splatterings should be removed with wooden or plastic scrapers (not metal), which will not scratch the surface.

Chemical attack. Chemical attack occurs when acid or alkaline materials come in contact with aluminum finishes, especially an anodized finish. The most common occurrence is encountered when mortar or muriatic acid is allowed to dwell, even for a short time, on a window or aluminum building component. Once the finish is visually affected, irreversible damage has occurred and the discolored item may need to be replaced.

Contact with strong cleaners. If strong cleaners are used to clean brick work and masonry, they should be confined to the area being cleaned. Cleaners strong enough to dissolve mortar spots on brick will surely damage any aluminum finish and possibly the underlying metal. Accidental contact from these solutions should be flushed from the aluminum surface immediately with clean water.

Welding fluxes. Welding fluxes can cause damage to aluminum during installation, and should be immediately flushed from the surface with water if accidental contact is made. Care also should be taken to ensure heat generated during welding does not affect the finish. Applying high temperature to anodize and painted coatings can permanently damage or discolor the finish.

Tar roofing. When tar roofing is applied, the roofing should be graveled on the same day to minimize staining from run-down. Failure to avoid contact with the aluminum will result in staining that is extremely difficult to remove.

It is crucial that aluminum work be carefully protected after the installation is complete and prior to the buildings final acceptance.

Most damage to aluminum work will occur during this time. Installed aluminum work is considered a "finished product" while the other building components are generally in a rough or unfinished state. Aluminum materials, therefore, must be well protected and shielded since it is often impossible to satisfactorily repair damaged materials in the field. Even if possible, rework is costly and can lack the quality of the original work. Likewise, replacement is time consuming and expensive.