- Location
- Ontario, Canada
A good friend of mine whom is a chemist and also worked in the aluminum industry for much of his life was also part of the R&D on the GM aluminum body parts experimental alloy rolling. He said that GM figured out a coating that as far as I know, they still use on the mild steel areas of the bodies that won't allow the panels to rust. But, he also said it was designed to have just enough resiliency to last 10 years before it has seen enough road debris, sand, salt, whatever it gets exposed to and lets the body metal begin to rot. Initially they had a hard time getting it to fill out properly on corners and it would either not cover or be the thinnest point that easily would chip off and begin rusting. I forget what he said they did to correct that, either rounded the corners or a slight change in the chemical composition to make it thicken when it began to curtain and not fall off...but once they figured it out there was a noticeable increase on GM vehicles living in rust prone environments that were not showing much rust after 5,6, 7 years and had no aftermarket under coating to help prevent it. But the 10 year old vehicles were showing up with a lot of rot. It was a strategy GM opted for to encourage perpetual annual sales that worked pretty much on par.
