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How to hard anodize the inside of a closed end shock tube the same thickness as the outside


I am an owner of an anodizing shop and I have a shock tube about 12 inches long and closed on one end. The diameter is about 2 inches. The customer wants the part Hard Anodized. They want the inside of the tube 1 mil buildup.My question is how can I get that buildup on the inside all the way down the tube. Any help would be appreciated. I have about 1000 of these parts.

Jeff Stewart

First of two simultaneous responses -- 2006

If it is completely closed on one end, just processing it thru all of the tanks and rinses is going to be difficult as well as time consuming.
I had a limited exposure to hard anodize, but I have doubts if you will have a uniform thickness the full length of the ID. sounds like a part that will require special fixturing and an internal cathode for a quality product. I hope you have not priced it yet.

James Watts
Navarre, Florida

Second of two simultaneous responses -- 2006

It will be a challenge for 1000 pieces, but the best way to accomplish this is to insert a small diameter cathode rod inside of the tube during processing, obviously being very careful that the cathode rod doesn't touch the inside of the tube.

Marc Green
Marc Green
anodizer - Boise, Idaho


Insert an cathode is a way though, I would prefer to block the outside of the part. Just like putting the part inside another tube which diameter has to be calculated, it would be easier practically.

John Hu

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