FYI, the paint companies have all been messing with their paint formulas to remove heavy amounts of VOC, that will result in lacquer not really having the traits the lacquer of old had. People who use Krylon have been saying their stuff is awful now. Supposedly the cans of lacquer are not lacquer at all anymore.
I know for a fact house paint has gone the same way, just try to get the most expensive paint you can buy now for exterior to last even 1/3 as long as it used to, impossible. Now it splits after 3 years, before, it stayed elastic for 15+ years, the only thing that made it come off was the old paint underneath lifting it loose.
I agree with the prep comments as to why paint washed right off, no paint does that if properly applied. You must have some hellacious acid rain there. I've got Duplicolor on cars and it's been there for many years and we have pretty high concentration of acid rain here.
Rust 'treatment' is a waste of time to me, the rust always shows back up and because part of the treatment is usually water based or miscible, again to lower VOC emissions and pollution. I glassbead or sandblast big rust spots to 100% remove every atom of rust. That or completely cutting the affected part out is all that will completely stop it.