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Mil-Spec: MIL-A-8625E

Type II and IIB coatings are the result of treating aluminum and aluminum alloys electrolytically in a bathe containing sulfuric acid to produce a uniform anodic coating that can range in thickness from .00005 to .0003. When specified this coating can be uniformly dyed or pigmented by exposure to a solution of a suitable type dye of stain.

Class/TypeThicknessComments

Type III.002 unless specified otherwiseUnless otherwise specified, coating will be sealed. Metal salt sealants should not be used on items that will be painted.
Class 1Non-dyed
Class 2Dyed.
Shall not be applied to aluminum alloys with over 5.0% copper, 7.0% silicon, or totally alloying constituents over 7.5%.Class 1. When class 1 is specified, sealing shall be accomplished by immersion in a sodium or potassium dichromate, in boiling deionized water, cobalt or nickel acetate, or other suitable chemical solutions.Class 2. When class 2 is specified, sealing shall be accomplished after dyeing by immersion in a nickel or cobalt acetate, boiling deionized water, duplex sealing with hot aqueous solutions of nickel acetate and sodium dichromate, or other suitable chemical solutions.

ASTM Designation: B 580

Anodic Oxide Coatings on Aluminum

Type
Coating
Minimum Fil Thickness (µm)
A
Engineering Hard Coat
50
B
Architectural Class I
18
C
Architectural Class II
10
D
Automotive – Exterior
8
E
Interior – Moderate Abrasion
5
F
Interior – Limited Abrasion
3
G
Chromic Acid
1

 

Definition of Service Conditions and Examples of Typical Applications and Applicable Coating Types

SC No

Definition

Typical Applications
Applicable Coating Types
Very Severe (5)
Exposure to atmospheric weathering that can be expected to extend for many years or to prolonged high bearing load wear conditions.Unmaintained exterior architectural facades, machinery parts, marine
A and B
Severe (4)
Exposure that includes likely damage from denting, scratching, and abrasive wear coupled with corrosive environments1-Automotive – exterior, 2-maintained architectural exterior facades, windows
C and D
Moderate (3)
Exposure that is likely to include occasional wetting with coating subject to moderate wear or abrasion.Lighting reflectors – exterior, athletic equipment, appliances, nameplates, lawn furniture
E
Mild (2)
Exposure indoors in normally dry atmospheres with coating subject to minimum wear of abrasion.Automotive – interior, houseware items, lighting reflectors – enclosed.
F
Crevice Condition (1)
Exposure to humid atmospheres with little or not abrasive conditions. Particularly for lap joints.Spot-welded or reviteed assemblies such as aircraft and electronic components.
G

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