> So what is "galling"?
Basically, the surfaces weld themselves together (similar to vacuum welding
which was a bugaboo of the early space program) in spots. If you apply
enough force, the metal tears, leaving fragments still welded into the
threads which then bind as you continue to turn the fastener. The welding
is exactly what anti-seize prevents.
>From http://www.boltscience.com
>>>
GALLING
An severe form of adhesive wear which occurs during sliding contact of one
surface relative to another. Clumps of one part stick to the mating part and
break away from the surface. (Can frequently occur when both the nut and
bolt are zinc coated.)
<<<
BTW if the studs broke even with brass nuts, chances are the studs
themselves were weakened, possibly by a long-ago exhaust leak eroding the
section through the gasket. They do have to be replaced occasionally.
Randall
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