Just ran across this on an old post in samsmarine.com...
As one who has removed hundreds (maybe thousands by now) of galvanically frozen SS bolts from aluminum, bronze, stainless, and titanium parts
over the 32 years I've worked at the Scripps Institution of Oceanography machine shop, I have some expertise in this area.
As mentioned by others, oil
, low heat, and shock sometimes works. But not usually. And it usually destroys the part you're trying to save.
There's another way.......
If applying heat with a flame torch, heat the FASTENER (if it's sticking out of the parent part) instead of the parent aluminum. Heat it fast, and heat it yellow hot. The idea is to soften the fastener at a time when It's too big (from thermal expansion) for the (still cold) hole it's in. This is easier than you think as the oxide layer between the parts
is a thermal insulator. When the fastener turns butter soft from the heat it plastically deforms to a smaller size, and the heat/cool cycle also breaks up the molecular bond between the fastener and the threaded hole. While the part is still hot (but not glowing) apply Moly-Dee tapping fluid to the threads. Use real Moly-Dee, accept no substitutes! If the first attempt is not successful, Moly-Dee may be completely washed out of the work area with acetone, most cutting fluids can not be removed easily, if at all.
The heat will cause the Moly-Dee to rapidly "wick" down the threads, and it's presence will prevent galling the softened threads during removal
. After cooling
, the fastener can usually be simply spun out with your fingers.
The BEST way to remove galvanically frozen fasteners is to find someone who is an artist with a tig welder. Have him weld up a "handle" out of droplets on top of the fastener making sure to heat the fastener yellow hot in the process. This works on fasteners broken flush, or even below the surface. I've removed plenty of microscope sized fasteners this way.
It is also the only civilized way to pull blind pins out of holes. For pins weld a small slide hammer to the end of the pin.
Taps broken in holes usually split along the long axis, make sure to weld all the pieces together before adding handle droplets so they don't "wedge" against each other during removal
Follow with Moly-Dee as above