Sources Rema O"Ch 452:2
Ba'er Heitev 14
[NB: citation from Shach from YD 95]
Sha'ar HaTziyyun 23, 24
The Rema recommends "nahagu" never kashering an unkosher Ben Yomo
Pot? Why in case the water is less than 60 times that pot, it's a problem
This concern does not seem to be Talmudic. Nevertheless the Mishnah Brurah does treat this concern as a "gzeira" lest one mag'i'll a vessel in less than 1/60. A classic g'zeira formulation.
So mei'iqqar hadin as long as one has enough volume of water to make 60 times the problematic pot, it's OK to do hag'alah l'chatchilah.
However, the Rema presents us with a policy to not exploit this and to wait a day - at least l'chat'chila.