I've read the other rust posts and no one seems to have addressed this issue (or I'm missing something. There seems discussion on rusthrough and new panel rust.)
I bought an old farm truck (a '47 International to be exact) which has never seen the inside of a shed or barn. Its from Sask. Canada and so it doesn't have any rust holes or soft spots but the paint has basically warn away leaving an overall rust. I have seen salvage yard cars (especially pre-war cars) in similar condition.
In fact, the hood and fenders now on my '55 sedan were like this. I don't know what kind of prep the body shop did a year ago but obviously it wasn't adequate, since I can notice telltale flaws in the finish that say rust to me. You must realize of course that this lame shop took 6 months to paint my car nearly always storing it outside - even when it rained. {Obviously, I didn't do enough checking)
The question is this... Are these panels worth trying to paint? Is this were the Zero Rust / Por 15 comes into play? Can you sand down to good metal? Is this a sandblast or chemdip arrangement?
