Yellow Oxide Paint

[Trip]

Several weeks ago, i acquired a very original M38 frame. The gentleman I bought it from also had a few misc. items that went with it. One item was the original master cylinder.

This past week as I was cleaning and sand blasting the master cylinder, I discovered it was originally painted the flat yellow oxide.

Today i am doing the same thing to an Autolite 24 volt regulator. It appeared to be black but as the thin black coat was coming off, I discovered what appears to be flat yellow oxide paint!

Can anyone verify these regulators were once upon a time painted with the yellow oxide or is this some kind of weird corrosive effect from the electrical system?

Trip

[mdainsd]

Yellow oxide primer as you referred to, is often used on aluminum parts. Notice aircraft are universally primed with that color primer.

The autolite regulator is of aluminum construction so no surprise there. I have found many coated that way.

The WWII Jeeps had aluminum master cylinders. My recollection is that they switched to cast iron near the end of the war. Is you M/C aluminum?

[Trip]

Good point.

The M/C I have does not appear to be Aluminium. It is too heavy. It has these markings on
one side:
FE2693
U.S.A
?47
AND:
wagner
lockheed

1DIA.
on the other side.

Is the yellow oxide primer the same paint used to mark other parts on M38 (s) such as the rear light housings, the front blackout lights in the grill and various other parts?

Thanks for your help.

trip

[wesk]

The yellow or very light greenish paint used for many years to prime anything aluminum was Zinc Chromate. It has drawn the ire of the EPA and has been pretty much replaced with Zinc Phosphate. The chromate does better on field work and yes it is harder to find and cost more. The phosphate is adequate when the aluminum is properly cleaned and prepped. The most common prep is Alumaprep which is also pricey nowadays.

The very early M38's had aluminum master cylinders from Willys factory. If you look in your ORD 9 the aluminum 7697478 master cylinder is illustrated on page 237 and the cast iron master cylinder 7416478 is illustrated on page 238.

[mdainsd]

Found another place that primer was used. The bullets for the front blackout markers are painted with it before OD.

[4x4M38]

Probably because of the non-ferrous material (I call it pot metal) they are made of. The rear housings are made of the same stuff as is I think the Bendix light housings. I believe the levers are cast aluminum, but might be the same stuff.