Tech Tip: Anodization

TECHTIP

Other Considerations

Mill Finish and Performance

Aluminum with a mill nish, or bare aluminum,

is the natural nish that extrusions have as they

emerge from the extruder die. No additional

surface preparation is applied.

Aluminum oxidizes over time with a light white

powder as it is exposed to air and moisture.

Oxidization is accelerated under very moist,

acid or salty conditions, generating a pitted

surface. While the surface of the natural

aluminum changes with exposure, there is no

signicant structural or mechanical impact to

the integrity or performance of the aluminum.

Anodizing is a highly controlled oxidation where the porous surface oxide layer is “sealed” to complete

the process. Sealing is accomplished by submerging the aluminum in warm water which hydrates the

oxide and shrinks the pores. Putting dyes in the water during the process allows it to permeate the

oxide layer, adding color to the aluminum surface.

Painted Surfaces

While a properly prepared surface can

be painted to provide a sleek nish, it will

deteriorate over the life of the solar array due to

exposure to weather and seasonal heat cycling.

For aluminum, painting is more expensive and

less durable than anodization.

Colored Anodized Aluminum

Environmental Impacts

According to the Aluminum Association, about one-third of all aluminum produced in the U.S. is from

recycled sources, saving some 95 percent of the energy required to produce aluminum from raw

materials.

Under Environmental Protection Agency rules, conventional anodizing generates no hazardous

waste; it does not use volatile organic compounds (VOCs) or EPA-listed toxic organics. Heavy metals

are dramatically lower than exterior-use paint pigments or plating. Recyclability is unaltered by

anodizing and no intermediate processing is needed for anodized metal to re-enter the recycle chain.

Paint peeling on an aluminum surface.

Oxidized almunium on wheel rim.