"Spot" reanodizing

[nprice]

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

 

[MintJulep]

I suppose you could conceivably build a dam of some sulphuric acid resistant material around the bare area and spot anodize in-place.

Removing the acid and dam, getting everything clean and sealing afterwards might be a bit of a challenge.

 

[IRstuff]

You could try gun bluing, which can be applied with cotton swabs or balls.

TTFN

FAQ731-376

 

[vennardd]

cant you just pick an anodize color farther down in the spectrum than the current color? this should change the fresh surface and the already anodized surface to the new color...i have done that to a part that needed a new color and it worked pretty well...the only difference is that i didnt have to deal with any unanodized surfaces, but it might be worth a try.

 

[swall]

Chromate conversion coatings, such as Alodine, are typically used to touch up and repair bare spots on anodized aluminum parts.

 

[unclesyd]

You could try brush anodizing on the affected area. Check with your anodize and see if he has the equipment to brush anodize. Also check with other anodizers and if you have an aircraft rework facility near you check with them.

With brush anodizing you will not get the hardest of the anodizing but you will get very good corrosion resistance.

If you just need the corrosion resistance they are chromate conversion coating pens available.

If it is essential to have hard anodizing you can mask off there areas that need protected and just anodize your reworked areas using a strippable coating.

http://www.strippablecoating.com/plating.aspx