I saw an episode on Wheeler Dealers ( was a different brand of car ) where Ed Welded in a metal patch , on a strut tower .

I think I would clean as much as I could , then weld up the cracks . Clean up the welds & then prime & apply corrosion proofing .

Next I would cut another piece of metal and weld a doubler plate on top of the original sheet metal . With corrosion protection in between . Clean up the welds and apply corrosion protection .

I am personally glad I do not live in the "Rust Belt " .

God bless
Wyr