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Hi Bill, I know exactly what you mean. I have an '83 Chev truck that had that "disappearing paint" on it. The only difference is that it was blue. I assume you are talking a basic single stage paint and not the more recent basecoat/clearcoat paints where, after a few years the clear coat begins to peel off and you are left with a dull but still "painted" surface. The stuff I had was a terrible OEM paint job. I think it was back when GM was experimenting with waterborne enamels in order to reduce VOC emissions. In any event, the topcoat color just peeled away in many areas after only a few years, leaving the light grey primer. The primer did eventually begin to show rusting, although it actually held up well for quite a while. I let it go too far (for several years) and the rusting became very significant before I actually did something about it. Unless you have an awful lot of rusting present over large areas, I would try to keep as much of the original primer as possible. It really is very good despite the poor topcoat. Whatever rust you may have showing is probably extremely difficult to remove if it is anything like mine was. It would just laugh at 80 grit paper on a circular grinder...would hardly touch it! The most effective way to tackle such rust is by sandblasting. I would remove any remaining topcoat with a chemical stripper. I used a paste type, home variety, stripper by Kleen Strip that I got at Home Depot. Unless you use several heavy coats, it will not lift the primer. In some areas I was even able to get a lot of the topcoat off by putting on 2" wide strips of a good masking tape (the 3M blue stuff) and pulling off quickly. A lot of the damned old topcoat would come right off with it. After stripping the topcoat, spot sandblast any rusty areas to bright metal and spot prime those areas with a 2-part epoxy primer the same day. Wash down well with soap and water, dry, scuff with a scotchbrite pad all over, clean with a dedicated cleaner such as PPG's DX330 and proceed to topcoat. You'll have to make a judgment call as to how much of the original primer can be salvaged. If you have only 10 or 20% rust and the rest decent primer, I would save it. If you have only 10 or 20% decent primer remaining, then don't bother. If yours is anything like mine was, most of the primer that has not been directly exposed for several years will be in decent shape.  Rod
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