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HARD-COAT ALUMINUM ANODIZING (TYPE III ANODIZING)
Anodizing subjects a metal surface to electrolytic action in order to coat it with a thin protective or decorative film. To obtain a more durable exterior coating on aluminum parts through the process of anodizing, a process called hard-coat aluminum anodizing is used. This technique produces a smoother finished surface covered by a denser oxide coating than some other anodizing procedures.
Type III anodizing is performed on metal components in a bath of sulfuric acid with 180-200 grams per liter of acid in addition to a small amount of dissolved aluminum. At an operating temperature of 28-32 degrees Fahrenheit, the anodizing bath creates a porous aluminum oxide film on the surface of the aluminum thick enough to increase the hardness of surface. Current densities in the process of anodizing can range between 24 and 40 amps per square foot (ASF).
Advantages and Applications
Type III anodizing offers some significant benefits. Due to the long lasting nature of the application, in which a thick aluminum oxide layer forms, the coating lasts for extended periods and supplies an excellent level of corrosion resistance. It also furnishes resistance to daily abrasion and wear, as well as flame-resistance properties under most circumstances.
The exact corrosion resistance of hard-coat anodized aluminum is estimated to 500+ hours salt spray resistance according to international standards, namely ASTM B117. Furthermore, according to Taber Abraser industry standards, this type of material has high durability (Taber Abraser CS-17 1000 g). The electrical insulation values are calculated to be 20 degree C,4*10.15 ohm cm2 / cm, while the breakdown voltage resistance of hard-coat anodized aluminum amounts to over 1500 DC. In addition, this type of aluminum has a low rub coefficient of 0.095 and is resistant to temperatures until 2050 ℃.
Thanks to these qualities, type III anodizing suits parts used in many aspects of daily life, and also metal components utilized under highly specialized conditions in different industries. From aviation and aerospace, industrial machinery, electronics, petrochemicals, firearms, marine technologies and cookware, sporting goods, molds and more, hard-coat aluminum anodizing holds widespread utility.
Specifications And Materials
Today, a number of industrial and government specifications exist covering the process of anodizing. These regulations sometimes vary between different industries, but all the specifications refer to hard-coat anodizing using the universally accepted Type III designation.
As a general rule, the series of aluminum alloys that tolerate hard-coat anodizing include series 2000, 3000, 5000, 6000 and 7000. The 1000 series alloys are too soft to be hardcoated, whereas the 4000 series contains high silicon which forms black smut when anodized. Other die casting materials that can be successfully anodized include 214, 355 and 356 series.
Our Type III Anodizing Services
Bunty LLC offers Type III (hard) anodizing as a customer option for industrial coatings. We assist customers in achieving superb finishes that will remain on metal components under most environmental conditions for long periods of time. Our protocols for Type III anodizing allow for the manufacture of attractive black, green, blue or red coatings on metal components.
Our company performs rigorous process control by conducting any necessary testing, including acceptance testing, corrosion resistance, coating weight, and abrasion resistance. We adhere to guidelines provided by our customers and industry standards in order to produce coated parts that will meet precise specifications.
REGULAR ANODIZING (Type II Anodizing)
The other, more widespread type of anodizing is called Type II anodizing. Many sources refer to this process as “clean”, “conventional” or “commercial” anodizing. It also utilizes a sulfuric acid bath, but it creates a moderate layer of oxide on the surface of an aluminum part, less thick than the layer deposited during Type III anodizing.
This type of coating increases the resistance of the surface of metal to abrasion and enhances the hardness of the exterior to some extent. Thanks to these properties, it enjoys popularity in is many architectural applications and in the electronics industry. It is used for coating the surfaces of parts utilized in military equipment, computers, and industrial machines.
Our Type II Anodizing Services
Bunty LLC offers Type II anodizing services performed under controlled conditions. Our regular anodizing coating can be deposited on a variety of metal components and alloys to increase their resistance to corrosion and abrasion. To increase the decorative quality of the piece, the base coating can be further enhanced by applying a layer of dye in one of the following colors: red, blue, green, gold or black.
Other Materials
In addition to aluminum coating, Bunty LLC provides other coating services as well:
Black Oxide Coating
We furnish black oxide coatings on parts with surfaces composed of steel or copper alloys. The process will ensure uniform color and improve the resistance of the part to damage from corrosion or dimensional changes. The black oxide is formed by applying a chemical coating to the part’s exterior, and the coating causes a chemical reaction to occur on the surface which changes the color through the formation of black oxide.
Iron, Zinc and Manganese Phosphate Coatings
Iron, castings, and steel or steel-based surfaces may benefit from pre-treatment with a phosphate application before coating and painting. This preliminary treatment protects against corrosion and helps paint adhere to the metal.
We offer three different types of phosphate coatings that help protect these metal surfaces:
Iron phosphate: This treatment cleans the surface of aluminum and helps ferrous metals accept paint.
Zinc phosphate: This coating supplies some protection against rusting and may improve paint adherence, too.
Manganese phosphate: A great oil-base, this pre-treatment offers the best safeguard against galling and corrosion and also supplies a slippery quality to the finished part.
