How to Specify Aluminum Anodized Finishes

Every anodized finish is defined by a standardized Aluminum Association designation. These designations communicate the required mechanical finish, chemical pretreatment, anodic coating class, thickness, and color so anodizers and specifiers are working from the same specification. Anodizing specifications are written as a composite designation: a sequence of letters and numbers tracking the metal from raw fabrication to its final coating.

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The Core Reference Table

Almost all aluminum finishes are built by combining choices from three distinct stages. Use the tables below to build your blueprint code.

1. Mechanical Finishes (M)

Applied first to establish surface texture or eliminate surface defects.

Code	Finish Type	Common Application / Result
M10	Unspecified	As fabricated from the mill
M22	Specular-buffed	High-gloss, mirror-like surfaces
M32	Medium satin	Directionally textured / brushed finish

2. Chemical Finishes (C)

Pre-treatment baths that change the metal's level of matteness or brightness.

Code	Finish Type	Expected Result
C12	Inhibited chemical cleaned	Removes surface oils without etching
C22	Medium matte etch	Muted, non-reflective satin appearance
C31	Highly specular	Bright-dip bath for maximum gloss and luster
C32	Diffuse brite dip	Soft, glowing semi-gloss finish

3. Anodic Coatings (A)

The final electrochemical oxidation layer.

Code	Class / Type	Thickness Layer
A21	Protective and Decorative	Less than 0.4 mils thick (Clear)
A22	Protective and Decorative	Less than 0.4 mils thick (Integral Color)
A23	Protective and Decorative	Less than 0.4 mils thick (Impregnated color)
A31	Architectural Class II	0.4 - 0.7 mils thick (Clear)
A34	Architectural Class II	0.4 - 0.7 mils thick (Electrolytically deposited 2-step color)
A41	Architectural Class I	0.7 mil and thicker (Clear)
A44	Architectural Class I	0.7 mil and thicker (Electrolytically deposited 2-step color)

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How to Format a Composite Code

All composite designations are preceded by the letters AA to identify them as an Aluminum Association designation. String your sequence together in chronological order:

AA + Mechanical (M) + Chemical (C) + Anodic Coating (A)

Real-World Blueprint Examples

• Clear Architectural Satin: An Architectural Class II clear matte anodized finish translates to: AA-M10 C12 C22 A31.
• Textured Bronze Structure: An Architectural Class I textured medium bronze electrolytic deposition (2-step) would be designated: AA-M32 C12 C22 A44.
• High-Gloss Colored Finish: An Architectural Class I diffused brite electrolytic deposition and overdye (3-step) would be designated: AA-M10 C12 C32 A44/43.