Can this be fixed?

You can't weld aluminum to steel two different metals. But you can weld that aluminum patch back on.

 

Just use that patch that you tore off it would be a lot easier. You can probably get that welded back on for 150 bucks.

 

I'd think you might run into issues getting a decent bead being that you have painted steel in direct contact with the weld area. Easy to get porosity in aluminum welds.

 

Let the owner of the trailer make the decision.

 

Sure lol Eastwood welder with spool gun, argon and some elbow grease.
Don’t loose that piece, if it still has a curve to it than most trailer repair shops will be able to weld it back on.

 

It’s common for Canadian trailers to corrode in that area they just put a patch over it . Any trailer repair shop or auto body can handle it in a hour or less .

 

Let the shop fix it.

next time learn where your trailer is in relation to other trailers.