Did you check the inner seal ?
I think that would be a easy point
of entry for water and mud, also
if the snap ring is off (the one behind
the hub) it might allow the axle to move
away fron the inner seal and get water
and mud in there.
You might also use waterproof boat
trailer wheel bearing grease, helps to
prevent corosion and repels water.
Anti Seize, hmmm I dunno, does a good
job to prevent galling of the metal but I
don't know how good it's water repelent
quality is, might work, it can only get worse,
so you'll never know if you don't try it.
Wild