[Steve Tinker]

Its not just the breakdown of the anti corrosion paints / rubberising / galvanising etc etc that causes terminal rust, but also the questionable quality of the sheet steel that is used by the manufacturer in the initial build. You also see it in a lot of cheap knockoff body panels out of Eastern Europe and China.

One of the main reasons that Italian cars built in the 1960's thro the 1980's were more rust prone than earlier models is that the Italian government (+ the British and French) were trading with Communist Russia but didn't want paying in untradeable Roubles.
So the deal was that the Russians part paid in goods(?) - some of which was the poorest quality steel ever produced. The steel was used by all the Italian car manufacturers (Alfa, Fiat, Lancia, Maserati and even Ferrari) with disasterous results. The steel was low in quality and then shipped by sea so it was already dissolving when it was on the ships. Coupled with the Italian's famous disregard of anti corrosion coatings, the results was soon evident.
From 1969 thro 1990 I owned 6 Alfa's, 2 Fiats and a Lancia, and they didn't differ in rusting out, even when living in clement weather climes in South Africa and Australia.
They made the Brits rustproofing look quite good.....