Letter 30053

Hard Anodizing per MIL-A-8625 with chromic acid  

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Does Type III Class 2 "Hard" Anodizing per Mil-A-8625 [link is to spec at TechStreet] have to be sulfuric, or can it also be Chromate (it shall not be sealed)?

Stacie Temple
Contract Manufacturing - Hunstville, Alabama

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 Editor's note:        Mr. Probert is the    author of Aluminum How-To / Aluminio El Como

To add to what Robert said, Class 2 denotes a dying process, and to my knowledge, one cant 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

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