Post August 89 there is a rumour that the steel used was contaminated, but to be fair they all rust at the same rate unless it is pumped full of preservative.
My P38 for example is 20yrs old and has never been covered in Dinitrol or Waxoyl and lives outside, in her early years was a seaside motor and has absolutely no rust..
Considering how the early Disco's, built at the same time/place, turned to powder makes that rumour well founded
Rust resistance does seem to be the P38's claim to fame, pity LR couldn't follow it up.
nb. on the rusty Classic front, I had a '85 (one of the first EFI's) that had intergalactic mileage (& 15 PO's) but no serious corrosion & that didn't appear to have any post factory protection