Old Paint Help...

[Over59]

I stripped all the paint off my tongue and bumper. This is a 68 caravel and there were many pretty colors. However the last layer is a yellow paint which does not come off areas that look like surface rust. Even resists steel wool and power washer. Looks metalic like in areas. Could this be a por-15 type coating? Do I torch it off or por over it. I don't like the idea of some oxidation going on under my new paint job.
PS. Metal is in better shape than I had feared. Expect the worst, you'll party more.

[Pahaska]

The yellow may very well be zinc chromate. ZC is widely used on bare metal in the aircraft field to prevent corrosion.

[Over59]

Well I've hit it with everything but the grinder. Looks like I'll por 15 over it.
Thanks