help to identify metal

[vgecas]

hello all,

i have stumbled across strange alloy, maybe someone could help to identify it? is is a solder, used to solder metal to ceramics. soaking it in HCl did almost nothing, but after soaking it in diluted nitric (fresh sample), that solder turned almost cherry red. what kind of metal(i believe it is metal) turns red in nitric ??

i have found it on some old soviet "ceramic vacuum tubes". before soaking it looked like pale grey solder.

 

[Lou]

Looks like Pd braze.

 

[vgecas]

hello,

if it is a Pd brazing, then soaking in nitric should dissolve Pd, but then the stuff that is left is red, i am concerned what is it...