I ran into an unexpected problem today when I changed out my argon bottle. The nut on the CGA fitting was stuck to the nipple pretty aggresively. There were some signs of corrosion on the regulator body also. The last time that I changed the bottle, I had a hard time getting a good seal and I used the blue bubble goo for leak-checking pretty generously. The blue goo corroded the brass. I replaced the CGA nipple and nut and forced the nut off the old nipple. There was a fair amount of white powdery corrosion and crap in the space covered by the nut.
If you leakcheck your brass CGA fittings with the bubble solution, I would suggest cleaning up fairly carefully.
BobH