Aluminum extrusions hanging over anodizing tank

Anodized Aluminum Extrusions

Aluminum can be given many different types of finishes; from rough or patterned to a mirror finish. This can be accomplished with a variety of chemical and mechanical processes. The chemical processes include etching, bright dipping (also known as chemical polishing) and anodizing. Mechanical finishes can be achieved by sanding, polishing, buffing, tumbling, burnishing, abrasive blasting, or glass bead blasting.


When it comes to producing quality products that will last, Bonnell Aluminum offers a variety of anodizing treatments that deliver value, including acid etch anodizing. As a leader in aluminum and soft alloy extrusion, Bonnell Aluminum has the experience to ensure that your products have the right coating to address the specific needs of your intended application.

Available in both clear and electrolytic colors, Bonnell Aluminum has the in-house capabilities to provide run-to-run consistency.

Anodizing Process and Benefits

Anodizing is an electrochemical process that accelerates and thickens the naturally occurring protective oxide layer. The resulting reacted finish is integrated with the underlying aluminum for total bonding and unmatched adhesion. The anodic coating is part of the metal but has a porous structure that allows secondary infusion, such as coloring. Its benefits include:

  • Increased durability
  • Lower maintenance costs
  • Aesthetically pleasing appearance
  • No chipping
  • No peeling
  • No flaking
  • No fingerprints
  • No chalking

Mechanical Finishes

Buffing table at Newnan, GA manufacturing facility


Buffing is a mechanical finishing operation in which buffing compound containing aluminum oxide is applied to the surface of an aluminum extrusion by rotating fabric wheels for the purpose of removing minor imperfections and developing a lustrous finish.


Sanding develops a desirable scratch finish using either flat or spiral sanders and is strictly done for cosmetic purposes. The amount of metal removed is dependent upon the grit finish used.

Acid Etch Anodizing

Our acid etch anodizing treatment offers superior uniform matte finish that meets or exceeds all AAMA 611 specifications. The resulting product is free of the streaks caused by other processes. Also, the lower gloss reading reduces glare in bright sunlight. Other benefits include:

• Reduced etch time
• Reduced aluminum removal
• Effectively hidden extrusion lines, scuffs and die lines

Anodize Code Designation Cross-Reference




Finish Class


Finish
Code



Bonnell Finish Description

Aluminum
Association
Designation
Minimum
Coating
Thickness
(mil/µm)

Meets
MIL-A-
8625F*
Decorative
040
Bright Dip (B/Lite))
AA-M11-C31-A21
0.10 / 3
.
.
050
Buff & Bright Dip ()B/Lux)
AA-M11-M21-C31-A21
0.10 / 3
.
.
12286
15-Minute Clear Satin
AA-M12-C22-A21
0.15 / 4
.
.
12287
20-Minute Clear Satin
AA-M12-C22-A21
0.20 / 5
.
Architectural Class II
12283
30-Minute Clear Satin
AA-M12-C21-A31
0.40 / 10
.
Architectural Class I
12288
60-Minute Clear Satin
AA-M12-C21-A41
0.70 / 18
Yes
.
12036
Light Bronze 2-Step
AA-M12-C22-A44
0.70 / 18
Yes
.
40402
Medium Bronze 2-Step
AA-M12-C22-A44
0.70 / 18
Yes
.
40403
Dark Bronze 2-Step
AA-M12-C22-A44
0.70 / 18
Yes
.
40404
Black 2-Step
AA-M12-C22-A44
0.70 / 18
Yes
.
12339
Brushed Nickel Satin
AA-M35-C22-A44
0.70 / 18
Yes
.
3006
Brushed Nickel Bright
AA-M35-C22-A44
0.70 / 18
Yes
.


*These are our most popular anodizing finishes. Please contact your Customer Account Representative for other finishes.

Anodizing Specifications Table

Aluminum Association Standards for Anodized Architectural Aluminum

Because each type of anodizing offers different benefits and appearances, the Aluminum Association Designation System for aluminum finishes was created to clearly communicate specifications.

Mechanical Finishes (M)
As Fabricated
M10
Unspecified
M11*
Specular as fabricated
M12*
Nonspecular as fabricated
M1X
Other (to be specified)

Buffed
M20
Unspecified
M21*
Smooth specular
M22*
Specular
M2X
Other (to be specified)

Directional Textured
M30
Unspecified
M31
Fine satin
M32
Medium satin
M33
Coarse satin
M34
Hand rubbed
M35*
Brushed
M3X*
Other (to be specified)

Nondirectional Textured
M40
Unspecified
M41
Extra fine matte
M42
Fine matte
M43
Medium matte
M44
Coarse matte
M45
Fine shot blast
M46
Medium shot blast
M47
Coarse shot blast
M4X
Other (to be specified)
Chemical Finishes (C)
Nonetched Cleaned
C10
Unspecified
C11
Degreased
C12*
Inhibited chemical cleaned
C1X
Other (to be specified)

Etched
C20
Unspecified
C21*
Fine matte
C22*
Medium matte
C23*
Coarse matte
C2X
Other (to be specified)

Brightened
C30
Unspecified
C31*
Highly specular
C32*
Diffuse bright
C3X
Other (to be specified)

Chemical Coatings
C40
Unspecified
C41
Acid chromate-fluoride
C42
Acid chromate-fluoride-phosphate
C43
Alkaline chromate
C44
Nonchromate
C45
Nonrinsed chromate
C3X
Other (to be specified)
Anodic Coatings General
A10
Unspecified
A11
Preparation for other applied coatings
A12
Chromic acid anodic coatings
A13
Hard, wear- and abrasion- resistant coatings
A1X
Other (to be specified)

Protective and Decorative
Coatings less than 10µm (0.4 mil)
A21*
Clear
A22
Integral color
A23*
Impregnated color
A24
Electrolytically deposited color
A2X
Other (to be specified)

Architectural Class II
10-18µm (0.4-0.7 mil) Coating
A31*
Clear
A32
Integral color
A33*
Impregnated color
A34*
Electrolytically deposited color (nonblack)
A3X
Other (to be specified)

Architectural Class I
18µm (0.7 mil) and Thicker Anodic Coatings
A41*
Clear
A42
Integral color
A43*
Impregnated color
A44*
Electrolytically deposited color
A4X
Other (to be specified)

Resinous and Organic Coatings (R)
R10
Unspecified
R1X
Other (to be specified)


*Processes available through Bonnell Aluminum.

Type II Anodize: Comparative Performance Requirement By Specification

.
MIL-A-8625 TYPE II
AAMA 611
AAC-1119
Corrosion Resistance
336 Hours Salt Spray
(5% Salt Solution)
Class I = 3,000 hrs. Salt Spray
Class II = 1,000 hrs. Salt Spray
16 Hours: Copper
Accelerated-Salt Spray
Coating Weight
1,000 mg/ft2
Class I = 14.18 mg/cm2
Class II = 2.40 mg/cm2
20-40 g/m2
Coating Thickness
.0007"-.001"
Class I = .0007" mg/cm2
Class II = .0004" mg/cm2
8-15µm
(.0003"-.0006")
Light Fastness
(Color Only)
3 ΔE
5 ΔE
No visual change
Abrasion Resistance
n/a
Not degraded by
abrasive glass paper
n/a
.