Re-using/welding cages?

[Hana]

Hiya!
So, my boyfriend is good at blacksmithing and welding as he is studying it at college.
And we just had the idea that maybe we could get some cages from the tip/dump as there are always a few odd wire cages for sale there and he could weld some of them together nicely so that Treacle my syrian or maybe another hamster in the future could have a mantion house!
But then we had some concerns that made me think again:
Number 1 - would it be safe to get cages from the tip as you dont know what the previous animal died of? (Of course I will disinfect it thoroughly)
Number 2 - Will all the welding and the metal or whatever it is be safe to have on the cage? It wouldn't harm a hamster in anyway?

I think that is it, at first I thought it was a really good idea but now I'm not so sure; anyway I guess I'll see what you guys say. Thanks!