Anodize Black (MIL-A-8625); Type II or Type III (Hardcoat)

Hardcoat Black Anodize [MIL-A-8625] refers to a specific type of anodizing process for aluminum and its alloys. The standard, decorative black anodize is Type II.

Hardcoat anodizing, also known as Type III anodizing, differs from regular anodizing (Type II) in several ways:

Thickness and Hardness:

Regular Anodizing:
Produces a thinner oxide layer, typically ranging from 0.0002 to 0.0008 inches. This layer is suitable for decorative purposes and provides moderate protection.

Hardcoat Anodizing:
Creates a much thicker oxide layer, usually between 0.002 to 0.004 inches. This thicker layer offers enhanced wear and corrosion resistance, making it ideal for heavy-duty applications.

Process Conditions:

Regular Anodizing: Conducted at higher temperatures with lower voltage and shorter immersion times.

Hardcoat Anodizing: Involves lower bath temperatures, higher voltage, and longer immersion times to build a denser and harder anodized layer.

Applications:

Regular Anodizing: Commonly used for decorative finishes, consumer electronics, and architectural elements where aesthetic appeal and light protection are important1.

Hardcoat Anodizing: Used in aerospace, automotive, military, and industrial applications where parts are exposed to harsh environments and require superior durability3.

Sealing:

Regular Anodizing: Often sealed to enhance corrosion resistance and dye retention.

Hardcoat Anodizing: Typically is not sealed because sealing can reduce the hardness and wear resistance of the coating2.

These differences make hardcoat anodizing suitable for more demanding applications compared to regular anodizing.

Types and Classes:

Type II: Sulfuric acid anodizing (conventional).

Type III: Hardcoat

Class 2: Dyed black finish.

Coating thickness should be specified (e.g., 2.0 mils).

Examples of Industry Applications that use Type III Hardcoat:

Applications include satellite components (efficient heat radiation), optical equipment (stray light absorption), and architectural trimmings (aesthetics and abrasion resistance). Military uses this extensively to reduce light reflections on components such as aerospace components, medical instruments, and optical devices benefit from this process.

Materials:

Aluminum, magnesium, and titanium can be anodized.

Note that only aluminum series 5, 6, and 7 are suitable for anodizing.

Specifications:

MIL-A 8625 Type II Class II, or,  

MIL-A 8625 Type III (Harcoat) Class II

If you need further information, feel free to ask!