Rust between the mudguard and spot welded bracket

[Tigerfeet]

Has anyone got a tried and tested method of dealing with rust between the spot welded bracket and the muguard? My C15 has bulges in the front mudguard caused by rust expanding underneath, between the mudguard and the braket. And on the rear mudguard, the brackets are distorted by the expanding rust to the extent that one has broken loose at one side. I had thought that after dousing them in evaporust etc the problem was dealt with, but clearly six months later the rust is still growing.
The attached picture shows the distorted and partially liberated bracket after I had removed most of the rust build up. But I don't think I can get behind most of the other brackets.