Michael,
your running into the same problem that most owners of late 80's and early 90's deere owners had, bad paint, or if i refer to john deeres' brochure better, i think they referred to it as electrostatically applied powder paint. I think that is what i seen in the brochure i have. but basically, it is like a powder coat and your right, tough as nails where it didn't rust through at. I think from what i've read is they had a number of bad years of primer.
I re-did a 332 a year ago and am finishing up a '90 420 right now, and they were both the same way. Only way i've dealt with it is sand blasting it, then building up the rust spots with primer or filler, then sanding it smooth before painting.
I did have a friend of mine remove the paint off of some 420 rims in a caustic acid tank where he works, and it removed the paint very well after being in there a week or so, but it does nothing for rust.
nick
your running into the same problem that most owners of late 80's and early 90's deere owners had, bad paint, or if i refer to john deeres' brochure better, i think they referred to it as electrostatically applied powder paint. I think that is what i seen in the brochure i have. but basically, it is like a powder coat and your right, tough as nails where it didn't rust through at. I think from what i've read is they had a number of bad years of primer.
I re-did a 332 a year ago and am finishing up a '90 420 right now, and they were both the same way. Only way i've dealt with it is sand blasting it, then building up the rust spots with primer or filler, then sanding it smooth before painting.
I did have a friend of mine remove the paint off of some 420 rims in a caustic acid tank where he works, and it removed the paint very well after being in there a week or so, but it does nothing for rust.
nick