I had some flux in a chennier, and it would not shift no matter
how long I left it in the acid.
What kind of pickle are you using, and how hot? I’ve had tube filled
entirely from one end to the other in an inch long small diameter
piece clean up nicely. Took an hour or so, with fresh sodium
bisulphate pickle at a simmer just below boiling…
Oh, and I do have a steam cleaner which helps remove stray bits of
debris that might still have been in there, but poking a wire in
would have worked too.
If, instead, you’re using weak citric acid pickle, and using it
cold, well, you might have a problem…