Old rust removing soaking agent ... Kerosene , Marvel Mystery Oil , Automatic Transmission Fluid and Acetone 50-50 mix = super penetrating oil , soak in a covered container .
WD40 will work , any commerical penetrating oil .
The secrete is a long soak so the penetrant can get under the rust ...then use 0000 steel wool to polish all the surfaces , inside and out .
Saved many a die with super penetrating oil or kerosine soak and 0000 steel wool .
I avoid water...water causes rust ...just say no !
Gary