I discovered today that the auto tensioner looks extremely corroded. There are flakes of rust coming off the housing. Everything else under the hood looks fine except for a few bolts near the tensioner which show a bit of corrosion. I got out the Corrosion X and dosed the area pretty thoroughly, but I am concerned about what caused this. I have had my 2000 since November 2004, and try to be pretty careful about corrosion; this was not the first time that the Corrosion X has found its way under the hood. I've pulled the under car covers off a couple of times to clean, and this is the first I've seen anywhere. I did install the block heater when I first got the car, and it is fairly close to the tensioner, but that is the only work I have done in the area other than spraying the Corrosion X. Any comments or suggestions would be welcomed.