Simple Penetrating Fluid
On one of the machinist hobby sites they listed the
rates of penetration and foot pound releases:
Their most effective was transmission fluid and ammonia.
I can attest to its effectiveness.
I use this combo over my go-to-since 1967 Kroil:
A mixture of 7 parts of automatic transmission fluid
and 3 parts of ammonia. Note: since transmission
fluid is hydroscopic you must re-oil when parts are separated.
As for rust removal, again I have tested and used frequently, a bath
of white vinegar for total immersion. In a few hours or over
night you will see the rust gone. Then I neutralize with baking soda
and water. Do not leave in longer than necessary else the slime
Minimizes amount of clean metal that must be polished away.