solder recomemdation

I have touched on this before in the context of replacing sealants applied to sheet metal assemblies before or after powder coating. I mostly solved that issue with an epoxy material that heat cures and can be powder coated over. the name escapes me right now, made in the UK a California welding dealer stocks it. works well, however it does require a pre-cure before powder coating to work well.
anyways, the epoxy was a big improvement over applying silicone over the powder coating.
I have another related issue. we often do full seam mig welding of sheet metal assemblies so to make them air tight but it is way over kill and sometimes cosmetically challenged. I have wondered about the advantage/ practicality of a soldered seam. ie first assemble with spot welds or mig stiches then go back and solder the majority of the seams then powder coat. The solder would have to be good at gap filling and able to withstand 450 degrees.
does anyone have experience with this? and can provide a specific recommendation?
thanks

Solder will be fine at powder coat temps, not strong, but still solid enough to work. Expect to have flux residues and that to clean up though and i doubt it will play nicely with welding of any process too, might make more sense to just fixture the parts and solder them, with the right equipment its fast to do and once you have everything clean enough + a few goes you get great looking joints too.

Bare in mind you will have to use lead free solders though, nother quirk, some colours of powder coating will change colour over certain alloying elements in solder (orange turns yellow over silver solder seams), i found that out the hard way :-(