Rust damage to the body is not uncommon in states where salt is used on icy roads. Unfortunately there is not much that can be done about this issue other than to avoid the salt.
Car Problem Reports
Mitsubishi Eclipse Body Prone to Rust From Road Salt
Mitsubishi Eclipse Problem
Average Mileage: 120,500 mi (90,000 mi - 139,000 mi)
Visitor, 2002 Mitsubishi Eclipse, 125,000 mi
Undercarriage of the car is in pretty rough shape with tons rust and some rot. Floor under drivers seat had rot hole all the way through. Exhaust pipe rotted out and had to have a patch welded on. Exhaust sounded like a motorcycle was running inside of the car... Paint bubbled up on the front corner of the roof on drivers side. Passenger side rear quarter panel in front of tire started rotting out and had to be repaired. The oil pan had to be replaced a few years ago due to rotting out.
It has been driven in New England every year, but the rust/ rot seems a little excessive.
The rust on the roof was also repaired around 3 years ago, windshield had to be removed since the rust was underneath it.
The rot in the floor had to be cut out, it was approximately a 6 by 6 inch piece, when I tried to remove the right rear bolt on the drivers seat to take the seat out, the rotted floor broke off with the bolt... Floor had to be patched with a couple layers of sheet metal, riveted down and undercoated.
I've seen cars twice as old as this one with less rust problems.
rust damage above rear passenger tire for a few years now.
Visitor, 2003 Mitsubishi Eclipse, 128,000 mi
rust issues under the hood, core support and shock towers. Open rear seck lid and rust is apparent there also