Does this really need to be cut out and new metal installed?



I've sanded it down once and though I got it all out. Put a small amount of bondo where I sanded, sprayed it with primer, paint and clear. It came back about a month later.

 

It may be coming through from the back side. If so it will probably have to be cut out as rust will continue to spread unless all oxygen is removed from it.

 

Thanks Gary, that's what I was afraid of.