Removing tarnish from high voltage high vacuum feedthrough

[ChristofferB]

Hi!

I've just received this really nice NOS MDC vacuum feedthrough. It's a hollow 1/4" copper tube insulated through the vacuum flange by about 18mm of ceramic insulator.

I guess its hollow for high powered applications where the electrodes themselves has cooling water running in them. I'm unsure. I'm gonna seal it with a blob of Sn/Ag solder.

Either way, how would one go about removing the copper tarnish? Abrasives are bad, as fine particles are difficult to get rid of.

Maybe dilute hydrochloric acid or 30% acetic acid?

I'm worried about galvanic corrosion, and deterioration of the metal/ceramic seal...

Also, could anyone venture a guess on the max operating voltage?

Thanks in advance!

[Tomorokoshi]

That's tricky because of the special conditions. Perhaps one of the Deoxit series:

https://caig.com/

[ChristofferB]

That could be, I will look for an equivalent brand in the EU. Thanks!

Either way I will try not to expose the ceramic. The inside of the tube could be cleaned by just pushing liquid through a hose attached on each end, and the outside ends with a rag.

[vindoline]

Chris, it's not clear to me why you want to clean the copper. However, since you're a chemist, you can brush on a solution of sodium chloride and citric acid. That will strip the oxide off the copper.   I don’t imagine it will effect the copper/ceramic junction.