Anodizing Services for CNC Parts — Type II & III

What it is and when to specify it

Anodizing is an electrochemical process that grows a hard, porous oxide layer on the surface of aluminum instead of painting it on. The part is immersed in an acid electrolyte, the anodizing solution, and current is applied. The result is an anodized coating that becomes part of the metal itself, so it does not peel or flake, and it is the default anodizing finish for aluminum parts that need corrosion resistance, wear resistance, or a specific color.

You specify anodizing when a part will be handled, exposed, or seen. It suits enclosures, brackets, knobs, and heat sinks where appearance and surface protection matter together. Because the coating is electrically insulating and adds thickness, we check the dimensional impact against the drawing before and after finishing.

Anodizing specifications

The main types we specify are Type II (conventional) and Type III (hardcoat). Type II is the standard anodizing process for color and general protection, while Type III builds a thicker, harder layer for wear surfaces. Coating thickness and the exact anodizing color are confirmed per order against your drawing, rather than assumed.

• Color: clear or natural, black, and dyed colors are the common options; custom shades are quoted per order.
• Masking: threaded holes and mating faces can be masked where buildup must be controlled.
• Sealing: dyed anodizing is sealed to lock in color and improve corrosion resistance.

Because anodizing grows into and out of the surface, it changes critical dimensions. We review threads and press fits with the finisher and adjust the machining allowance so the finished part still meets tolerance.

Which materials and parts it suits

Anodizing is specific to aluminum. It is the standard finish for 6061 and 7075 aluminum machined parts, and it pairs naturally with enclosures, brackets, knobs, and heat sinks.

• Aluminum machined parts in 6061 or 7075.
• Enclosures and housings, brackets, and knobs where color and wear matter.
• Heat sinks, where the oxide layer protects while leaving most thermal performance intact.

Parts made from stainless steel, carbon steel, or brass and copper are not anodized and get their own finishes instead. Finishing is applied through our vetted partner network, managed under one quality process, and we stay your single point of contact so you do not need to vet anodizing companies yourself.

Corrosion, wear and dimensional impact

Anodizing improves corrosion and wear resistance on aluminum, with Type III hardcoat offering the most durable surface. The trade-off is dimensional. The anodized coating adds roughly half its thickness to each surface, so bores shrink and shafts grow, and threads are the usual risk point.

We handle that in two ways. First, we mask threads and tight-tolerance features where the drawing allows. Second, where the coating must be uniform, we build the thickness into the machining allowance so the finished anodized metal finish still holds ±0.01 mm on features that matter. We confirm the allowance with the finisher before quoting so there are no surprises at shipment.