Responsa על פסחים 60:10

Q. Is it permissible to scald large kneading-basins, which cannot be submerged in boiling water because of their size, by pouring boiling water over them [thus preparing them for use on Passover]?
A. No, but they may be filled with water and the water heated to the boiling point to render them fit for Passover use.
SOURCES: Pr. 439.