Surface finishes

Anodizing services

We offer anodizing type II and III, which are ideal surface finishes for aluminum parts. Anodizing strengthens aluminum parts and is available in several colors, depending on the type. All types of anodizing will increase the lead time and cost per part.

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What Is Anodizing?

Anodizing is a common electrolytic passivation process that is often used to grow the thickness of the natural oxide layer on the surface of metal parts. It improves corrosion and wear resistance and provides better adhesion for paint primers and glues than does bare or untreated metal. Anodizing changes the microscopic texture of the metal’s surface by changing the crystal structure of the metal. The process of forming an oxide film on metal products (anodes of aluminum or titanium) under the corresponding electrolyte and specific process conditions due to the applied current.

Anpllocnc supply custom high volume aluminum，titanium and other metal anodizing services. MIL-A-8625 Type II Class 1 and 2 sulfuric anodizing, Permodize® graphic anodizing,hard coating,corrosion resistant and wear resistant black anodizing services are available.

Aluminum alloys can be oxide coated in thicknesses up to 1.0 mil. Aluminum parts can be anodized in different color finishes. Applications include automotive, military and medical.

Anodizing type II

Surface preparation	Colors	Glossiness	Cosmetic availability	Thickness**	Visual appearance
As machined (Ra 3.2μm / Ra 126μin)	Clear, Black, Red, Blue, Orange, Gold	Glossy (Above 20 GU)	No	50μm to 150μm	Parts are anodized directly after machining. Machining marks will be visible.
Bead blasted	Clear, Black, Red, Blue, Orange, Gold	Matte (Below 10 GU)	Cosmetic on request	for clear: 8 to 12μm(0.0003” to 0.0004”) black and color: 12 to 16μm(0.0004” to 0.0006”)	Grainy texture, matte finish
Bead blasted	Clear, Black, Red, Blue, Orange, Gold	Glossy (Above 20 GU)	Cosmetic on request	for clear: 8 to 12μm(0.0003” to 0.0004”) black and color: 12 to 16μm(0.0004” to 0.0006”)	Grainy texture, glossy finish
Brushing(Ra 1.2μm / Ra 47μin)	Clear, Black, Red, Blue, Orange, Gold	Glossy (Above 20 GU)	Cosmetic on request	for clear: 8 to 12μm(0.0003” to 0.0004”) black and color: 12 to 16μm(0.0004” to 0.0006”)	Parts are manually brushed to reduce marks, then anodized. Brushing lines will be visible.

Anodizing type III

Surface preparation	Colors	Cosmetic availability	Thickness	Visual appearance
As machined (Ra 3.2μm / Ra 126μin)	Black, Natural (thicker layers will appear darker)	No	35 to 50μm(0.0013” to 0.0019”)	Parts are anodized directly after machining. Machining marks will be visible.

Non standard requests

We supply a range of standard colors (see Color options). If you need a particular RAL or Pantone color code, please contact [email protected]

As a standard our anodizing thickness will follow ISO 7599: ISO class AA10 (for clear) and ISO class AA15. If your parts require different standards, please contact [email protected]

Clear anodizing

We offer clear anodizing services that produces a translucent oxide layer that allows some of the underlying metal material to show through. It’s often used for engineering components, kitchen utensils and other parts where a natural look is desired.

Colour anodizing

We offer colour anodising services by colour dipping or electrolytic colouring. This type of anodizing is often used on external automotive parts, enclosures and other products where a decorative finish is desired.

Satin Hardcoat Anodizing (0.002″ Minimum Thickness)	Satin Sulfuric Dyed Anodizing (0.0004″ Minimum Thickness)
Black	Black
Non-Dyed	Blue
	Bronze
	Gold
	Grey
	Green
	Orange
	Red

Anodizing Advantages

Enhanced Durability

Anodizing creates a thick oxide layer on the aluminum surface. This layer, being much harder than the aluminum itself, offers enhanced protection against chipping, peeling, and scratching, ensuring the component’s longevity.

Corrosion Resistance

The protective oxide layer formed during the anodizing process acts as a barrier against environmental factors such as moisture, salts, or other corrosive agents. This protection ensures that aluminum parts remain unaffected by rust or corrosion, especially in challenging conditions.

Improved Aesthetics

Anodized aluminum surfaces can be dyed in a variety of colors. This flexibility in design choices, coupled with a rich metallic sheen, often results in a more attractive appearance than untreated or painted surfaces.

Electrical Insulation

The oxide layer that results from anodizing acts as an insulator. This insulation property can be crucial in electronic applications where specific components must be electrically non-conductive to function correctly.

Thermal Resistance

Certain types of anodizing can enhance the aluminum’s thermal insulation properties, making it ideal for applications where heat retention or dissipation is a factor.

Improved Lubrication

Certain types of anodizing, like Teflon-impregnated hardcoat anodizing, can improve the lubrication properties of aluminum parts, reducing friction in moving components.

About the Process

Anodizing is an electrochemical process that thickens a CNC machined parts natural oxide layer to make it thicker, denser, electrically non-conductive, and more durable.

This process can only be done using aluminum or titanium alloys because they conduct electricity well. During anodizing, the alloy is submerged in an acid electrolyte bath and acts as an anode. Once a cathode is placed in the anodizing tank and an electrical current passes through the acid, oxygen ions from the electrolyte and atoms from the alloy combine at the surface of the part.

Anodizing comes in two different varieties — Type II and Type III. The overall finishing process is the same, but Types II and III require that the part be submerged in a diluted sulfuric acid solution.

Anodizing Type II, also known as “decorative anodizing” (as the finished coating can be clear or colored), produces coatings up to 25 μm thick. The coating thickness range for clear parts is 4-8 μm and 8-12 μm for parts that have been dyed black. This process produces a part that is smooth, elegant, and resistant to corrosion and wear.

Anodizing Type III, also known as “hardcoat anodizing,” can produce anodic coatings up to 125 μm thick. Parts with this coating have high density and are even more wear-resistant than anodizing Type II.

All in all, anodized finishes are durable and promise good dimensional control. Anodized finishes are best used in high-performance engineering applications, particularly for internal cavities and small parts. They are among the most aesthetically pleasing finishes for CNC machined parts, but often come at a higher price tag.

Design considerations

Anodizing has insulative properties, so anodized parts have poor electrical conductivity.
All edges and corners on the workpiece should be rounded with a radius of no less than 0.5 mm, and no burrs are allowed. This prevents local overheating and burning of the workpiece caused by current concentration.
Workpieces with rough surfaces can become smoother after hard anodic oxidation treatment. However, workpieces already possessing an extremely smooth finish will lose some smoothness.
In the process of hard anodizing, the workpiece must bear high voltage and current. Special fixtures must, therefore, be designed to keep the workpiece in good conductive contact. It will otherwise break down or burn the contact parts of the workpiece.

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