13-08-2013, 02:42 PM
Once you have all the grot cut out it's well worth putting a coat of weld through zinc primer over all the areas you can see as you'll have unprotected edges where you've made the cuts that will start to rust again with condensation. It's well worth a light coat on the back of all repair patches to help slow down any future rust. You can get cavity wax in aerosols too that you can spray in through any access holes you an find. It can seem like a waste of money at the time since you can't see it but in a couple of years time the repair should still be near perfect.