Anodizing is a conversion of the aluminum surface to practically pure aluminum oxide: the anodic coating.  Type  II is of particular interest to the designer wishing for both the virtues of form and function. This anodic coating is significantly more abrasion and corrosion resistant then the untreated metal. The coating thickness is a combination of both penetration and build-up, in approximately a 50-50 ratio. This coating may be subsequently dyed in a variety of colors, imparting a very decorative finish both in a satin and a polished surface result. Color will vary from light gray to dark gray depending on alloy. Not as readily dyed as sulfuric anodize.

AMS 2472C listed as similar to this specification.

Type 1 & Type 1B coatings:

Class 1 200 Milligrams/sq.ft.

Because of thin deposit that will scratch easily. Can be used for inspection of aluminum forgings or castings by noting evidence of chromic acid bleed out from laps, cracks, seams, etc.

Typical thickness specified  0.00001"- 0.0007"

Type I Conventional coating produced from chromic acid bath. Unless otherwise specified, coating will be sealed. Metal salt sealants should not be used on items that will be painted.

Type 1 Low voltage chromic acid anodizing 22V.

Class 1 Non-dyed (Natural, boiling D.I. water sealing).

Class 2 Dyed.

Shall not be applied to aluminum alloys with over 5.0% copper, 7.0% silicon, or total 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)

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