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| Chromic Anodize | Mil Spec | Thickness | Comments |
| MIL-A-8625E | |||
| Color will vary from light gray to dark gray depending on alloy. Not as readily dyed as sulfuric anodize.
New salt spray requirement is 336 hours (5% solution per method 811 of FED-STD-No. 151). Minimum weight for Type 1 Coatings Because of thinness, will scratch easily. Can be used for inspection of aluminum forgings or casting by noting evidence of chromic acid bleed out from laps, cracks, seams, etc. |
Type 1
Class 1
|
.00005-.0003” | Unless otherwise specified, coating will be sealed. Metal salt sealants should not be used on items that will be painted. Non-dyed (Natural, including dichromate sealing). Dyed. Shall not be applied to aluminum alloys with over 5.0% copper, 7.0% silicon, or totally alloying constituents over 7.5%. When copper content is less than 4.6% and for all suitable casting alloys, be sure aluminum is tempered (such as –T4 or –T6) |
ASTM Designation: B 580
Anodic Oxide Coatings on Aluminum
Anodic Coatings Descriptions
NOTE: Hard coatings may vary in thickness from 12 µm to more than 100 µm. If the thickness of Type A is not specified it shall be 50 µm min. Type A coatings will not be sealed unless so specified.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 environments | 1-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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