Pipe cannot be opened because of rust

[avoy]

The photo show a pipe fitting.
The outer pipe is made of copper while is inner is apparently made of 203 steal.
However, the 203 steal become rusted and cannot be opened.
Is there a good way to open it without breaking it?
For instance, perhaps with some chemical etching methods that I can remove all the rust?

 

[Latexman]

Is that a grounding connection?

Penetrating oil. Let it soak in for some days.

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.

 

[Compositepro]

Scrape off as much corrosion as you can. I've found some benefit to torch heating the connection. This can help with differential expansion and it also dries water out of the joint. Then penetrating oil can soak into the rust more effectively (after cooling). Ulimately there is only brute force, intelligently applied. That means a saw to cut two radial slots through the nipple, being careful to not damage the threads in your nozzle. When trying to unscrew the stuck nipple apply hammer blows to the wrench in both directions. Turning in only one direction will cause the joint to lock-up again as the rust particles jam together, even if the joint started to move. The penetrant needs to fluidize the particles.

 

[LittleInch]

looks like a ball cock connection to me. Can't you just fix it by removing the end cap?

That's not worth the effort. Cut it off.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bimr]

Agree with Compositeprp. Use of an acetylene torch will expand the out ring and should free the joint. If the does not work, you may cut it off with a grinder.

 

[mk3223]

use torch with caution if it's not clear the condition inside the screwed pipe.
It looks that the copper fitting was screwed into a male threaded boss nozzle. Did you try to unscrew the copper fitting?

 

[chicopee]

Cut off with a grinder as close as possible to the outer pipe, then use a chisel and hammer to collapse the inner pipe without damaging the outer pipe inner threads. Once pieces of the inner pipe are removed rethread the outer pipe inner threads. You may have to enlarge the inner pipe diameter slightly to thin out its wall thickness before chiseling.