Anodizing

What is Anodizing

Anodizing is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts.

The process is called anodizing because the part to be treated forms the anode electrode of an electrolytic cell. Anodizing increases resistance to corrosion and wear, and provides better adhesion for paint primers and glues than bare metal does. Anodic films can also be used for several cosmetic effects, either with thick porous coatings that can absorb dyes or with thin transparent coatings that add reflected light wave interference effects.

There are several good reasons to consider anodizing your aluminum parts. When anodizing aluminum, a layer of oxide is created, forming a layer on the surface of the part. This layer is so thin that it doesn’t even materially impact the dimensions of precision machined parts. Because the oxide layer is harder than the aluminum, it protects the metal underneath it, making it scratch-resistant and increasing corrosion resistance.

The oxide layer is also rougher than the aluminum surface, making it possible to paint or dye the anodized aluminum. In fact, you can add any color you like to anodized aluminum parts. Coloring is accomplished either by using dyes during the anodizing process or by painting afterward. Dying is preferred, as it creates permanent coloration which means it won’t fade and can’t be scratched off.

Benefits of Anodizing Aluminum Parts

Anodizing aluminum parts provides many benefits, both in terms of aesthetics and the mechanics of the parts themselves.

Durability and Corrosion Resistance

On the mechanical side, the anodizing process makes the surface of the parts extremely durable. The oxide layer is fully integrated with the base layer. It is exceptionally hard and provides superior abrasion and corrosion protection. The thermal insulation properties are also outstanding. This is why aluminum extrusion products are commonly finished by anodizing.

Appearance

On the visual side, the effects of anodized aluminum are quite impressive and the finish is permanent. It is wear-resistant so it will never scratch or fade and will never need a touch-up. Metallic tones and vibrant colors can be achieved, giving anodized parts a sleek appearance.

Type I- Chromic Acid Anodizing

Chromic acid anodizing (Type I) uses chromic acid to create a thin oxide coating on aluminum parts, usually about 20-80 microinches thick, making it ideal for manufacturing components with tight tolerances. When properly sealed, Type I anodizing offers moderate durability and has excellent corrosion resistance. This flexible coating is able to withstand stress and flexing, and is often used in high-precision and critical industrial components.

Type II- Sulfuric Acid Anodizing

In sulfuric acid anodizing (Type II), sulfuric acid is used to produce a thicker oxide layer, usually between 100 and 1,000 microinches thick. Sulfuric acid anodizing allows for a wide range of anodized aluminum colors. Because it is both wear and corrosion resistant, this durable method is popular for applications where protection and aesthetic appeal are essential. It’s the primary method used in a variety of industries, including architecture, construction, and consumer product manufacturing.

Type III- Hard Anodizing

Like Type II, hard anodizing uses sulfuric acid to oxidize the outer layer. In Type III, lower temperatures and increased voltage result in a much thicker layer, typically exceeding 1,000 microinches. A Type III hard coat is exceptionally durable, but usually isn’t the best choice for components with tight tolerances, since some dimensional changes occur during anodization. Hard coat aluminum anodizing is common for parts exposed to extreme conditions, such as industrial equipment and heavy machinery.

Minimum cost is $100/ batch

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