The anodic oxide structure is entirely made of aluminum oxide and comes from the metal substrate. This aluminum oxide is not applied to the surface like paint or plating, but is instead totally integrated with the underlying aluminum substrate, preventing it from chipping or peeling.
It features a highly organized, porous structure that permits subsequent operations such as dyeing and sealing.
Aluminum is anodized by submerging it in an acid electrolyte bath and running an electric current through the solution.
A cathode is positioned on the interior of the anodizing tank, and metal serves as the anode. Oxygen ions are released from the electrolyte and unite with aluminum atoms on the surface of the anodized component. Therefore, anodizing is a matter of highly regulated oxidation, the augmentation of a natural phenomenon.
Anodized finishes on parts such as LT4 Supercharger Lids or Lt4 Valve Covers, have elevated aluminum to one of the most revered and commonly utilized materials in the manufacturing of hundreds for consumer, commercial, and industrial items.
Various Forms of Anodizing Aluminum Parts
There are three common anodizing processes, and each produces a unique set of practical and aesthetic qualities.
Type I – Anodize with Chromic Acid
An electrical current (anodizing) is passed through a chromic acid solution during Type I Chromic Acid Anodizing. This produces a thin aluminum oxide film that is nonreactive, an excellent primer foundation, and resistant to corrosion. This is the preferred coating for high-stress components, such as those used in the aerospace sector.
Type II – Sulfuric Acid Anodize
During the Type II anodizing process, the metal is immersed in a sulfuric bath, which builds up aluminum oxide on the surface as well as within the aluminum substance. This process’ incorporation into the metal creates an intriguing feature of the aluminum oxide that makes it an excellent electrical insulator.
This dielectric property imparted by anodizing will allow aluminum to endure 800 volts per 0.001″ of build-up thickness for type II anodizing.
In addition to limiting conductivity and guarding against corrosion, this oxide layer can also be colored in a variety of hues, offering the final product significant ornamental finish options. Type II anodizing is the common term derived from Mil-A-8625, a military standard specification.
Type III – Anodize Hardcoat
This type of anodizing, also known as hard coat anodizing or hard anodizing, is used to increase the wear and corrosion resistance, surface hardness, and thermal and diachronic qualities of aluminum objects. With Type III anodizing, the capacity to retain lubricants, PTFE coatings (such as Sanford HardlubeTM), also improves.
On aluminum surfaces, hard coat anodizing enhances the thickness of the naturally existing oxide layer. Typically, the thickness of natural oxide layers is between 2 and 3 nanometers; with Type III anodizing, this thickness can be extended to or above 50 m* (0.002″) When properly applied, hard anodic coatings provide a very regular and homogeneous layer throughout the entire treated object’s surface.
Type III anodizing is an abbreviation derived from the Type III category of the Mil-A-8625 standard.
* μm = micrometer (1000x the length of a nanometer)
Anodizing Pros
• Both the top and bottom are complete
• More intriguing/unique.
• Reveals more machining marks.
• The finish has a lot of personality.
Anodizing Cons
• More difficult/intricate procedure.
• Finding a dependable, rapid-response partner can be difficult.
• More expensive
• Possibility of yellowing with time
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