Stainless Steel bodywork - How?

Hello from a newbie - I joined up specifically to ask you guys about the stainless steel (304 grade?) bodywork of the Delorean cars. How exactly did they prevent corrosion? I've welded 304 material into rusted out floorpans of regular cars in the past and whilst the 304 stayed solid, it got a kind of surface corrosion after a while. (It would brush off, so maybe it was something else on the surface of the 304 that corroded..) Also, when I've welded 304 material to other 304 material, the weld itself has always gone rusty. How was this prevented on Delorean cars? Or is there no welding? I'm really intrigued as to how this was done and why it's not been repeated..

Thanks,

Neil

i believe there is no welding but thats just me ask around some more