Advanced finishes:
Environmental benefits of extruded aluminum
Wendell Nash and Bill Bishop,
Posted
11/01/2009
New
painting and coating processes for extruded aluminum products offer
unmatched environmental advantages for the green building and
construction industry. Versatile,strong and long-lasting,
extruded aluminum is the material of choice for architects and
contractors.In addition to its flat-rolled form, which is easily
fabricated, aluminum can be extruded into virtually any constant
cross-sectional shape in continuous lengths. Applications range
from building and column coverings to windows and doors to railing
systems, divider panels, decorative trim, fencing and more.
Aluminum's attractive and corrosion-resistant natural finish never
needs painting and is virtually maintenance free. Now, new
technologies for powder coating and anodizing are expanding the
design possibilities and aesthetic benefits of architectural
aluminum products.
Powder Coating
Environmentally Friendly and Durable with Wide Color
Choices
Compared to liquid painting, powder coating is a solvent-free
process that uses no volatile organic compounds that are
detrimental to the environment. It is available in a wide selection
of colors and gloss values, all offering superior corrosion and
weather resistance, as well as durability. Starting with a clean
metal surface,products are pretreated with a five-stage phosphate
process. Next, resins (binding agents that form the surface) are
applied in combination with pigments for color and strong
coverage,fillers for specific properties, and hardeners to increase
the surface strength. Painted parts are oven cured at 375 F (190 C)
for at least 20 minutes. The newest powder coating materials can be
finished under lower temperatures, reducing energy
consumption.
Sapa Extrusions operates advanced powder coating facilities at many
of its 16North American plants. At Gainesville, Ga., the company's
Eco-Powder Coating system uses dual powder coating booths, each
with 32 oscillating guns and an operating system that quickly
adapts to a variety of customer shapes and specifications. The line
can paint 25- foot- (8-m-) long extrusions at speeds up t25 feet
per minute. The process utilizes over 97 percent of the coating
material by reclaiming overspray to minimize material waste and
reduce environmental impact.
Powder coating is unique for painted extrusions that meet or exceed
AAMA 2603, -04 or-05 standards and is also RoHS compliant. The
coatings can uphold specified color and gloss during 1,500 to 4,000
hours of accelerated salt spray corrosion tests. These coatings can
also be tailored to meet solar reflectance requirements and reduce
heat island effects in more developed spaces. Overall, powder
coating provides environmentally conscious industrial finishes,
creating sustainable products that are visually pleasing and
corrosion resistant.
Anodic
Coatings
Superior Finish Without Hazardous
By-products
Anodizing is one of the most environmentally friendly metal
finishing processes. As the green finish for aluminum, anodizing is
the controlled electrochemical process that converts the barrier
layer of aluminum into aluminum oxide.
Aluminum parts are immersed in a sulfuric acid electrolyte and
electrical current is passed through the solution to produce
aluminum oxideon the parts. The resulting aluminum oxide film is
similar in hardness to a ruby or sapphire.The anodic coating is
formed from the barrier layer of the substrate aluminum (the
coating is actually part of the metal), not an externally applied
substance such as paint. The porosity of the aluminum oxide allows
for subsequent finishing with electrolytically deposited color or
any number of dyed finishes.
The process produces no hazardous byproducts- many of the process
baths (which are filtered by a dedicated process) are reused or
recycled. The recycled acid etch by-product has several industrial
applications.
Sapa plants in Portland, Ore., and Delhi, La., use Sapa Select
advanced acid etch processes installed in 2009. An improved process
over traditional caustic soda etch, Sapa Select hides metal
imperfections (streaks, die lines, etc.) and provides a superior
uniform matte finish. The surface has gloss readings from 4.0 to
6.0, compared to caustic etch readings typically from 9.0 to 18.0.
In addition, Sapa Select removes 90 percent less aluminum during
processing, advantageous when tight tolerances are required, and
leads to an 85 percent reduction in the amount of landfill waste
sludge.
Using traditional sulfuric/dye equipment,anodizing is available in
Clear, Gold and Black, and Brite Dip (chemical polish) finishes in
lengths to 18 feet (5 m). Fine, medium and coarse matte etched
finishes are offered in clear, as well as the full range of
architectural bronze colors (Champagne to Black) are available up
to 30 feet (9 m) in length. For applications requiring extreme
abrasion resistance, hardcoat anodizing is available. All anodized
finishes provided by Sapa Extrusions meet or exceed the
requirements AAMA 611-98 and/ or military specification
MIL-A-8625F.
Green
Aluminum
Recycled and Recyclable
Many Sapa facilities now offer Sapa Green billet on request with
external/internal recycled content that exceeds the U.S. Green
Building Council's LEED Standards. Remarkably, 75 percent of all
aluminum produced since 1888 is still in use.
With its recyclability, ease of fabrication, environmentally
friendly coatings and finishes,aluminum extrusions are the natural
choice for versatility, economy and beauty in a wide range of
architectural and building applications.
Wendell Nash is the paint manager at Sapa
Extrusions in Gainesville, Ga., and Bill Bishop is
the anodizing manager at Sapa Extrusions in Portland, Ore. For more
information, go to www.sapagroup.com.
www.sapagroup.com