Aly/Steel corrosion repair - rear fuel tank outrigger bracket

I've cut off the rear fuel tank outrigger on my 2A ready to weld a new one on. I can save the bracket that holds it to the tub by two bolts, but where this bracket has sat against the tub I've got some nasty corrosion.

I'm unsure how to go about repairing this. Is that part of a section I can replace and rivet in? Or is it part of a much larger section? I've never had a rear tub off so I'm not sure what's what here.

HI Ive just put my tub back on, ive been doing painting the chassis but the lower half of the tank outrigger was gone so I made one to fit and welded it to chassis frame and upperpart of outrigger.
I think you would need to cut out the bad area on chassis and weld a plate in for strength then weld the outrigger onto that.

This is the bracket I mean. It's bolted to the ally of the tub, is that right?

I didn't follow you steve but don't know if it's because I didn't explain well enough or am too numpty to follow what you're saying.

i think I didint understand you, we were looking at same bracket , so sounds like the ally tub has gone where it touched the steel (differential corrosion i had a bit of that too) in that case would be to reinforce over with some ally plate riveted on ,

Well here's the plate, without rivets for now. I need to tack the old bracket to the new outrigger then remove it to put a weld around it. I also had some repair to do to the rail first.

It feels, sort of, bodgey..? But I can't honestly think of another option without having the tub right off and dealing with it concourse style (and it's not that kind of project).

Any better ideas very welcome.

Looks good, will be invisible once its got 1/8" of unverseal over it!