Quote Originally Posted by UVB76 View Post
What do you reckon if I sprayed some Penetrol on the surface rust areas, and around the welds? Would this cause a problem when heating up or with the aluminised mild steel?
I wouldn't worry about it, especially on the inside. Penetrol will only burn off anyway. Spray the nuts and bolts with Penetrol about an hour before you want to undo them. Spray the outside after you have fitted it with HT paint as suggested by TD's.
The welding is probably just a couple of tacks to hold the flange in position while the main weld was done, assuming it is welded on the other side of the flange.