"Spot" re-anodizing

I have a anodized and painted part which I need to have work done on. It is part of a pressure vessel and the area around the connector o- rings are too rough. There is a fear that they may leak under pressure. I do not wnat to have the entire part stripped, for fear that other critical dimesions may be pushed out of their tolerance range. Are there any ways to re-anodize only the fresh surfaces after the are machined smoother? What haappens when you put an already anodized part with fresh surfaces into a bath?
Any help?
- Nick

On Thu, 29 Nov 2007 15:47:59 -0800 (PST), " snipped-for-privacy@gmail.com"
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Aluminum anodizing is an oxidation process, that leaves micro-porous hard pockets (if the electrolyte is kept cool)
After a dye-dip (nylon dyes are sometimes used on a small scale) the object is immersed in hot water to seal the pores and render the color relatively fast.
The oxide coat is progressively higher resistance as it gets thicker. I imagine (not having tried it,) that if you spot machine a patch then re-anodize, the current will go mostly to the fresh spot. Matching the dye shade would be quite a trick though.... But perhaps you really do mean paint?
Brian Whatcott Altus OK

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Most of the current should go to the unanodized area, as the resistance is much lower. There may be a couple of issues though. a) what will the caustic soaps do to the part on the pre-cleaning end of things, and b) the anodizer will need to watch the current, flow and time very carefully as to prevent burn-out.

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Nick, I see two issues.
First, to anodize a part there must be an point of attachment for the electric supply wire, (I know bad wording, but it gets the point). So, if you only have a spot face there is no other place to attach.
Second, Anodizing uses acid, sometimes Sulphuric, Can your paint resist immersion?
If you just need a protective coat look into "Alodine". It does not require electrical current. Dave

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Good idea Dave, alodining can also be DIY if you want to test it or just do it yourself. One product from memory is called "Accella Gold" made by Turco Chemicals. The stuff I used was a simple clean and dip process.