Hi guys,

I am trying to re-hab an old Curtis air tank for home shop use @ 125 psi.
It is OLD, as in rolled plate, riveted, with the seam filled with a
silver color metal.
The drain bung is almost rusted out, so I drilled and tapped it for
1/2'' pipe,
still only 1/8'' thread. Will weld in a bushing for 3/8" pipe to fit a
drain cock.

Question is: does anyone here have an idea what the silver filler is? It
seems too hard for solder.

Thanks, wws.