What color was a vehicles hull under the zimmeritt where it has been chipped away? I've seen models where it is primer red, dunklegelb and bare steel. Does anyone know what is correct?

Jesse

Oldbean, I believe it is conceivable that all three are correct. As Zimmeritt was applied in the field and the factory, if the coating failed do to adhesion then the “base coat” paint would be visible. If the “failure” was due to a projectile strike bare metal could be exposed.

Zimmerit was also applied directly to Zinc Oxide primer, before paint.

Ah, chipped zimmerit. This question pops up all the time on modelling boards.
First thing to understand is how zimmerit was applied. This goes a long way to explaining what might be seen if it chips. Zimmerit was applied in two coats. The first coat was applied over primer with very little imprinting, just a bit of scoring to give the second coat some 'bite.' This coat would then be dried with blow torches, because if left to air-dry, days would be required. The second coat was applied roughly 24 hours later. This coat received the pattern imprinting (varied according to vehicle, time-period, and factory).
Now, armed with this knowledge, what would appear in chipped areas? The answer: depends. There are basically four possibilities: 1.)Bare metal if the chipping was very heavy, pulling off both layers of zimmerit as well as the underlying primer; 2.)Primer if again the chipping was heavy enough to pull off both layers of zimmerit; 3.)The first layer of zimmerit if the chipping only pulled off the top layer. This would expose the underlying zimmerit layer which is said to have varied from an approximate color of dunkelgelb to a grayish/cream color. Early in its use, zimmerit had ochre pigment added to acheive something close to dunkelgelb. This practice was dropped as it was a senseless use of a pigment that became more scarce as the war progressed. From that point on the substance had the aforementioned grayish/cream color. 4.)The chips may be oversprayed or painted in the field or at maintenance yards. In this case, of course you wouldn't see any difference from the surrounding areas.
Photographic evidence supports all of these possibilities. If you see a vehicle in which the underlying areas appear much lighter than the surrounding areas, #3 would apply. Ron Volstad's painting on DML's early Panther A is an example of this. Squadron's Panther in Action has multiple photos of this vehicle and it is clear that the chipped areas are much lighter than the rest of the vehicle. Personally, I believe #2 and #3 would be the most common. Primer had excellent adhesion, so it would take quite a bit of damage to strip it off. I would personally reserve the bare metal effect for edges or around battle damage. #4 would also be fairly uncommon because the attrition rate of German vehicles during the zimmerit period was quite high. I'd imagine that it was not all that common for such vehicles to be repainted.

Okay, then what color is the primer?

Red Oxide. In my opinion, Polly Scale has the best match in acrylics, while Floquil's railroad line has the best match in enamels. I believe one, or perhaps both, is called Oxide Red.

Once again, the gang at armorama has come to the rescue. Thanks to everyone for the info.

Jesse