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Hard Anodizing per MIL-A-8625 with chromic acid

Q. Does Type III Class 2 "Hard" Anodizing per MIL-A-8625 / MIL-PRF-8625 [on DLA] have to be sulfuric, or can it also be Chromate (it shall not be sealed)?

Stacie Temple
Contract Manufacturing - Hunstville, Alabama
2004

A. Hard Coat may be sulfuric, oxalic, or a combination, but you cannot get hard coat thickness with Chromic Acid Anodizing.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2004

A. To add to what Robert said, Class 2 denotes a dying process, and to my knowledge, one can't dye chromic acid anodizing, nor oxalic acid anodizing (oxalic acid anodizing may be able to be dyed, but in 17 years of experience, I've never come across it). I'd go with the sulfuric.

Marc Green
anodizer - Boise, Idaho
2004

A. As it happens, oxalic acid is used for the anodization of ID plate stock for screen printing and such by at least one big company.

Wyndon Evans
- Lago Vista, Texas
August 3, 2016

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