kalibrgun Cricket Colibri and P-Rod airtube material

Hummm,
I dont think Crosman will tell you EXACTLY what they use, wouldn't think the others would ( Bother to ) either. 
You could take a good guess if your a metal type person and likely be close but .

As long as the metal passes testing it gets used.

"last forever" NOPE. Nothing lasts that long.
Most manufacturers don't ever recommend testing or inspection ( in the US ) of air vessels on our rifles. I've seen 20 year old tubes that look like they've never been used, and a 2 yr old tube with corrosion you could ruin a finger nail on.
Safety is always up to you.

Might I inquire what's on you mind exactly? Considering a build? Looking for a heirloom rifle? Other?

John