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Anodized coating
Anodized_Coating  

Mil Spec 8625 F

Type I A
Conventional coatings produced from chromic acid bath

Thickness
 0.5µ-7.6µ

Type I B
Low voltage chromic acid anodizing (20 volts)
Used for 7xxx series alloys

 0.5µ-7.6µ

Type II
Conventional coatings produced from sulfuric acid bath

1.8µ-25.4µ

Type III
Hard coat (Uniform anodic coatings)

12.7µ-115µ

  • Class 1
    • Non dyed

 

  • Class 2
    • Dyed

 

Test Methods For Type II Anodized Aluminum

Oxide Coating Thickness

ASTM B 244-79
ASTM B 487-85

                       Min Thickness
    Class I        18 Microns
    Class II       10 Microns

Oxide Coating Weight and Apparent Density

ASTM B 137-89

                     Min Weight     Min Density
    Class I     4.18 mg/cm2    2.32 g/cm3
    Class II     2.40 mg/cm2     2.32 g/cm3
     

Adopted from AMAA 611

Corrosion Resistance

    ASTM B 117-90

                       Min Hours         Max Spots
      Class I       3000                  15
      Class II     1000                 15

Seal Quality

    ASTM B 136-77
    ASTM B 680-80
    ISO 3210

                         Max Weight Loss
      Class I       40 mg/dm2
      Class II       40 mg/dm2

Aluminum Alloy Reference for Anodizing

Series

(AA)*

Alloying

Constituants

Metal

Properties

Coating

Properties

Uses

A.Q.**

Types

Non-A.Q.**

 Types

1xxx

None

soft
conductive

clear
bright

cans
architectural

none

1100, 1175

Finishing advice: care should be taken when racking this soft material; good for bright coatings; susceptible to etch staining;

2xxx

Copper

very strong
hard low
elongation

yellow
poor protection

aircraft
mechanical

none

2011, 2017 2219, 2224

Finishing advice: since copper content is >2%, these produce yellow, poor weather-resistant coatings; don't mix with other alloys on load;

3xxx

Manganese

strong
small grains

grayish-brown

cans
architectural
lighting

none

3003, 3004

Finishing advice: difficult to match sheet-to-sheet (varying degrees of gray/brown); used extensively for lighting;

4xxx

Silicon

strong
fluid

dark gray

architectural
welding wire

none

4043, 4343

Finishing advice: produce heavy black smut which is hard to remove; 4043 & 4543 used for architectural dark gray finishes in past years;

5xxx

Magnesium

strong
ductile
fluid

clear
good protection

architectural
welding wire
lighting

5005, 5657

5052, 5252

Finishing advice: for 5005-keep silicon<0.1% and magnesium between 0.7% and 0.9%; watch for oxide streaks; 5005 used extensively for architectural;

6xxx

Magnesium & Silicon

strong
ductile

clear
good protection

architectural
structural

6063, 6463

6061, 6101

Finishing advice: matte-iron>0.2%; bright-iron<0.1%; 6063 best match for 5005; 6463 best for chemical brightening;

7xxx

Zinc

very strong

clear
good protection

automotive

none

7029, 7046 7075

Finishing advice: zinc over 5% will produce brown tinted coating; watch zinc in effluent stream; good for bright coatings;

* AA - Aluminum Association
** A.Q. - Anodizing Quality - material suitable for architectural anodizing applications

TYPE I "Chromic Acid"

Color will vary from clear to dark gray depending on alloy. Copper bearing alloys only yield gray colors. Not as readily dyed as sulfuric anodize due to thinness of coating.

New salt spray requirement is 336 hours (5% solution per method 811 or FED-STD-No. 151).

Type I

Type IB

Type IC

Chromic acid anodized coating. This process is used principally for the treatment of aircraft parts. An example is the Bengough-Stewart process where a 30 - 50 g/l chromic acid bath is maintained at 100° F and the voltage is gradually raised to 50V. Adjustments are made for high copper, zinc, and silicon alloys. Coating weights must be greater than 200 mg/ft2. Criteria for corrosion resistance, paint adhesion, and paint adhesion testing must be specified.

Low voltage (22)2V) chromic acid anodized coating. Typically associated with higher temperature, more concentrated chromic acid electrolytes. Coating weights must be greater than 200 mg/ft2. Criteria for corrosion resistance, paint adhesion, and paint adhesion testing must be specified.

Anodized coating produced in a non-chromic acid electrolyte. As with other Type I coating processes, the treatment is designed to impart corrosion resistance, paint adhesion, and/or fatigue resistance to an aluminum part. Coating weights must fall between 200 - 700 mg/ft2. Criteria for corrosion resistance, paint adhesion, and paint adhesion testing must be specified.

TYPE II "Sulfuric Acid"

MECHANICAL FINISHING

    As Fabricated

 

    Buffed

 

    Directional
    Textured

 

 

 

CHEMICAL FINISHING

    Nonetched Cleaning

 

    Etched

    Brightened

 

ANODIC COATING

    General

    Decorative

       Less than 10u

 

 

 

 

    Architectural
    Class 2

       10u-18u

 

    Architectural
    Class 1

       18u and more

 

A.A.

M-10

M-12

M-21

M-22

M-31

M-32

M-33

M-35

 

C-11

C-12

C-22

C-31

C-32

 

A-11

A-21

A-211

A-212

A-213

A-23

A-24

A-31

A-33

A-34

A-41

A-43

A-44

COMMON

 

 

 

 

 

 

 

 

 

 

 

R-1

R-5

 

 

 

 

200

201

202

 

 

204

 

 

215

 

 

DESCRIPTION

Unspecified

Nonspecular as fabricated

Smooth specular

Specular

Fine satin

Medium satin

Coarse satin

Brushed

 

Degreased

Inhibited chemical cleaned

Medium matte

Highly specular

Diffuse bright

 

Prep for other applied coatings

Clear coating 2.5u-7.5u

Clear coating min. 2.5u

Clear coating min. 5u

Clear coating min. 7.5u mil

Coating with impregnated color

Coating with Electrolytically

Clear coating

Coating with impregnated color

Coating with electrolytically

Clear coating

Coating with impregnated color

Coating with electrolytically

EXAMPLES OF FINISHING METHODS

 

No particular reflectiveness.

Polished first with coarser than 320 grit, followed by 320 grit, then buffed with Alum oxide.

Buffed with Alum oxide compound.

Sanded with 320-400 grit Alum oxide.

Sanded with 180-220 grit Alum oxide.

Sanded with 80-100 grit Alum oxide.

Brushed with stainless steel wire brush.

 

Organic solvent treated.

Soap cleaner only.

Sodium hydroxide (caustic soda) 30-45 gr/li @ 60°-65° C for 5 min.

Chemical bright dip solution of the proprietary phosphoric-nitric acid type, or electropolishing.

Etched finish C-22 followed by Brightened finish C-31.

 

15% Sulfuric acid @ 20° C, 12 amps/sq ft. for 10 min. Sometimes not sealed.

15% Sulfuric acid @ 20° C, 12 amps/sq ft.

15% Sulfuric acid @ 20° C, 12 amps/sq ft. for 10 min.

15% Sulfuric acid @ 20° C, 12 amps/sq ft. for 15 min.

15% Sulfuric acid @ 20° C, 12 amps/sq ft. for 20 min.

15% Sulfuric acid @ 20° C, 12 amps/sq ft. , followed by dyeing with organic or inorganic colors.

15% Sulfuric acid @ 20° C, 12 amps/sq ft. , deposited color followed by deposition of inorganic metallic salts.

15% Sulfuric acid @ 20° C, 12 amps/sq ft.

15% Sulfuric acid @ 20° C, 12 amps/sq ft. for 30 min., followed by dyeing withorganic or inorganic colors.

15% Sulfuric acid @ 20° C, 12 amps/sq ft. deposited color for 30 min., followed by deposition of inorganic metallic salts.

15% Sulfuric acid @ 20° C, 12 amps/sq ft.

15% Sulfuric acid @ 20° C, 12 amps/sq ft. for 60 min., followed by dyeing with organic or inorganic colors.

15% Sulfuric acid @ 20° C, 12 amps/sq ft. deposited color for 60 min., followed by deposition of inorganic metallic salts.

Data derived from "Designation System for Aluminum Finishes" (DAF45), published by The Aluminum Association.

TYPE III "Hard Coating"

Color will vary from light tan to black depending on alloy and thickness. Color overtones listed below may vary with the use of additives and/or the process. Can be dyed in darker colors depending on thickness. Coating PENETRATES base metal as much as builds up on the surface. The term THICKNESS includes both the buildup and penetration. Provides very hard ceramic type coating. Abrasion resistance will vary with alloy and thickness of coating. Good dielectric properties. Corrosion resistance is good, but recommend sealing in 5% dichromate solution where increased corrosion resistance is required. Where extreme abrasion resistance is required do not seal as some softening is encountered.

Type III Anodize Thickness Guide

Alloy      Major        Maximum       Color***
         Constituent   Thickness*   Overtones
                         (in)

1100   99.5% pure Alum.  .003       **Gray/Green
2011       Copper        Not recommended
2014       Copper        .001         Bronze
2017       Copper        .001         Bronze
2024       Copper        .0015        Bronze
3003     Manganese       .002           Gray
4032     Silicon        .0012          Gray
5005     Magnesium       .0035        Gray/Brown
5052     Magnesium       .0035        Gray/Brown
5083     Magnesium       .0035        Gray/Brown
6061   Mag/Silicon      .003         Dark Gray
6063   Mag/Silicon      .004           Green
6105   Mag/Silicon      .0035        Gray/Green

Alloy      Major        Maximum     Color***
         Constituent   Thickness*   Overtones
                         (in)

6262     Mag/Silicon     .0025         Gray
6463     Mag/Silicon     .003          Gray
7075         Zinc        .004        Bronze
355        Silicon       .0035         Gray
356        Silicon       .0035         Gray
357        Silicon       .0035         Gray
360        Silicon       .0005         Gray
380        Silicon       .0005         Gray
319        Silicon       .0025       Light Gray
MIC-6      Silicon       .0035       Dark Gray

50% Penetration and 50% Buildup per Surface
* Generally Accepted
** Over .0025" Thick
*** May vary
 

 

 

© 2001 Aluminum Anodizers Council