Porsche 944s and 928s are far more rust resistant than most American or Japanese cars of the 80s or even 90s. Likewise with Volvos. The classic 911 was an old design that went through iterative improvements, and the 964 is better rust-proofed than most American or Japanese cars of the late 80s or 90s. Old Audis tend to have minimal rust, and old Mercedes-Benzes like the W126, W124, and W201, while they certainly can and do rust, their bodies tend to far outlast Japanese and American cars of the same era driven in similar conditions. Old W124s still soldier on as daily drivers and winter beaters in the cold and salty environments of post-Soviet states with mostly OK bodies, whereas Japanese cars of the 1980s almost all rotted away beyond repair being worthwhile more than a decade ago.

It is my impression that older Mercedes are pretty good in this department.

I still see so many mid-80's Accords in the US. Yes, there's probably a somewhat smaller share of them that survived than mid-80's BMWs, but there's a lot of factors that go into survival (Honda == cheaper to keep going as a beater; BMW == higher initial value / treated nicer for the earlier parts of its lifespan).

You see so many mid 80s Accords in the US for the same reason you still see a lot of 90s Caddys despite them being objectively crap cars. The people who bought them could afford to keep them nice, not beat the shit out of them and maintain them as they needed it so they lasted. Your average 1990ish Accord commuter sedan lived a far, far, far easier life, at least for the first 10-15yr than your average Ford Taurus or Subaru Legacy family wagon and it shows in the number that are still around today.

This is the same reason you see a lot more Grand Marquis and Town Cars to (non-cop) Crown Vics today than you did back when they were still making all those things. I cite this example specifically to control for literally every variable except the owners.

> Accord commuter sedan lived a far, far, far easier life

I think you've got this backwards when you're looking at the mid-80's. The Accord was very much a bottom-of-the-barrel option that didn't get as nice of care as most cars-- certainly compared to the European imports that you're comparing to. Especially e.g. probability of being garaged.

I came here to mention E-coat, though I'm thinking of it by another name, it's why in dry climates it's rare to see vintage fords rusted out, GM and Chrysler took longer to implement it.