Where do Vehicles Rust the Most?
If you’ve been following this blog for long, you know that vehicles rust the most in what’s called the ‘salt belt,’ which means anywhere road maintenance crews put salt or other deicing chemicals on the roads to help keep us all from slipping on the ice and crashing into one another. But where on the vehicle itself does the most rust occur? Kevin Read, coauthor of the travel blog Travel with Kevin and Ruth, native of Ottawa, Ontario, Canada, and 20-year veteran of the auto body and paint industry, gives this answer:
Cars almost always rust in the same places: seams, and the lower six inches of any panel.
Before that, he explains that while all rust is essentially the same, for practical purposes we can think of it as coming in two different kinds:
Cars can have two different types of rust. There is “surface” rust, and there is “structural” rust. It’s actually the same rust, but we call it different names because of where it appears. Surface rust is what you might see if you get a stone chip on your hood or a scratch that goes right through the paint. And after a couple of years it starts to bubble. It’s unsightly, but it’s not a structural problem. And surface rust takes many many years to become an actual rust hole. Structural rust happens at seams and normally starts on the inside of a panel where you can’t even see it. Even though you can’t see it, it’s the worst type of rust. Because the rust starts on the inside of the panel, by the time you see it, it has worked it’s way from the inside to the outside, and now it’s a rust hole!
So the rust Kevin’s talking about here, occurring at seams and in the lower six inches of any panel, is structural rust. Obviously, stone chips and scratches can happen anywhere. Seam rust happens because brine (salty water splashed onto the vehicle from winter roadways) seeps into the tiny cracks and crevices of the seams and gets trapped there. It’s harder for the brine to fall off, and it takes much longer to evaporate, than on the smooth body surfaces with no crevices or other features. Lower body panel rust happens because that’s what takes the brunt of all the splashing and rock-throwing from the tires. In fact, speaking of stone chips, the rocker panels and the bottoms of the door panels really take a beating if you drive on gravel roads. Combine gravel roads with winter deicing brine, and you’ve got a recipe for rust. Kevin has the tools, time and patience to take his little blue car apart every year, spray it with rustproofing and put it back together again. Judging from her responses to the rustproofing post’s comments, Ruth seems to be very proud of him, and rightly so. For Canadians who are not intrepid do-it-yourselfers, he recommends the rustproofing chain Krown (Kevin uses Krown’s product, himself). New Hampshire’s equivalent to Krown is NH Oil Undercoating. They use the same basic product (although at The Rust Stop Pros, the exact formula is subject to change in response to changes in automotive technology and deicing trends), and they apply it in basically the same way.