Anodizing Equipment / Aluminum Finishing
Walgren is a world leader in the development and adaptation of anodizing equipment for precision
applications. Walgren anodizing equipment is used worldwide for these processes:
- Chromic acid: Type I, also known as CAA or Chromic Acid Anodize, was the first
commercial anodizing process. It is primarily used to generate a thin film, (.05 to .1 mils) on parts
with complex geometries and exceptionally tight tolerances. Type I anodizing is compatible with
most alloys and is widely used in aerospace and defense, and wherever critical components
have lap joints, recesses, crevices or other features which can trap electrolyte.
- Type II, SAA, or Sulfuric Acid Anodize is the most frequently used aluminum
anodizing process. It produces coatings up to 1 mil for conventional coatings. Conventional coatings are primarily decorative or protective.
- Hard coat: Type III, HCA or hardcoat anodizing processes at higher voltages and current densities. It generates up to 4 mils for hard coatings, and has the highest wear performance - generally Rockwell 60-70C. It produces the smoothest surface and the darkest coloring, and is primarily used for engineering applications.
- Phosphoric acid: PAA, phosphoric acid anodizing is also Boeing's BAC5555 process. It is used for structural adhesive bonding, per ASTM-D3933, and substantially improves
performance in high-humidity environments.
- Boric & Sulfuric acid: BSAA, Boric Sulfuric Acid anodize, The Boeing Company
developed this process as a chromic acid anodizing replacement for non-critical fatigue parts. Known as BAC 5632, its acceptance grew as environmental laws increasingly favored the use
of chrome-free chemistries. Paint adhesion is equal or superior to chromic acid, and the process
is more energy-efficient than chrome-based processes.
- Thin film sulfuric acid (TFSAA)
- Titanium anodizing
- Tartaric acid anodizing
- Chem film
- Bright dip
- Dye penetrant inspection
All of these anodizing processes use controlled electrolytic oxidation to develop a tenacious aluminum
oxide coating on the surface of an aluminum sheet or component. Anodizing becomes integral to the
substrate: it forms by "growing down" into the metal (about 1/3) and by superficial deposit (about 2/3).
Anodizing substantially increases resistance to corrosion, scratching and wear, provides insulation, maintains high reflectivity, and enhances appearance: coatings are transparent to gray and resist staining. Anodizing can be used alone, and can achieve a variety of color and texture effects through dyeing, electrocolor or interference color.
Some of the world class companies that use Walgren anodizing equipment include Bell Helicopter, Goodrich, Boeing, Alcoa, and the USAF.
See these pages for information on Walgren Anodize technology as it applies to these industries:
Medical Components Anodizing, Stainless Steel Passivation, Electropolish
Military and Aerospace Anodizing