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Anodized castings came out kelly green

2003

We received castings that were processed per MIL-A-8625 / MIL-PRF-8625 [on DLA] TYPE 2 class 1 they came in a Kelly green color rather then clear? The vendor said this is from the sealing process. My knowledge of finishing is minimal my question, is this coloration normal?

Raymond Zajackowski
- North Wales, Pennsylvania, USA

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First of two simultaneous responses

Green? I've seen some strange coloration from various sealants, however, Kelly green isn't one of them. My guess would be that the firm had a big run of green anodize just prior to your job. The nickel acetate seal had leached a considerable amount of green dye from the previous job and deposited it in your freshly anodized, more porous castings. The fact that they're castings would make them more prone to this.

Sodium dichromate would be orange / yellow in color. Standard nickel or cobalt acetate, generally used for sealing any dyed anodize, would impart no coloration (normally) and hot DI water seal too would add no color. You've got a strange one and the above scenario is the only one I can foresee.

Anodically speaking, good luck! Maybe it's a St. Patrick's Day thing!

Milt Stevenson, Jr.
Syracuse, New York
2003

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Second of two simultaneous responses

Please come back to us and tell us what is the alloy of the castings. Meanwhile, be advised that a dichromate seal on Type II will come out "Kelly Green".

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2003

That is normal if dichromate seal is used.

Dado Macapagal
- Toronto
2003

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Additional information: the material was an Al. Alloy investment casting A356 class 2

The parts were sealed with a dichromate seal. Thanks everyone for your help.

Raymond Zajackowski
- North Wales, Pennsylvania, USA
2003

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Nothing in MIL-A-8625 says Class 1 coatings shall be clear. The requirement is "non-dyed". Dichromate seals can take on a greenish tint. Para.# 3.5 "The characteristic color imparted by the sealing process shall also be considered as non-dyed."

Chris Jurey, Past-President IHAA
Luke Engineering & Mfg. Co. Inc.

Wadsworth, Ohio

2003