Lanny,
As a last resort, try the soak in
Evaporust I suggested earlier. I think you can buy a quart at Advanced Auto or some such for less than $10. That should be more than enough to immerse the rusty part. Just another test procedure. (After soaking it in water, it'll probably need this.)
If it doesn't work, I'll pay for the
Evaporust next time I see you.
Denny