For what it is worth, I really don't think that zinc chromate was ever used as an interior paint for wooden railroad cars. Among other things it seems to have been developed in the 1920's as a corrosion inhibitor mainly used on iron and aluminum (especially aircraft interiors, as anyone who built 1/48 scale monogram model airplanes as a kid can attest to) and it is not cheap. Railroads were painting the interiors of cabooses, outfit cars and locomotive cabs green well before the 1920's, railroads were not known for using anything but the cheapest paints and pigments on non-revenue cars and zinc chromate's corrosion inhibiting properties would be of little to no use on wood.
That said, zinc chromate was used in railroad cars, many lightweight passenger cars from the 1940's and 1950's utilized aluminum for the interior wall and ceiling panels and all of it was primed with zinc chromate as seen below;
A section of luggage rack from AT&SF 2865, built by Pullman in 1947. Note the zinc chromate primer applied to the aluminum panels used to make the shelf.
While the color is arguably similar to some wood railcar interior paints, all of the zinc chromate paint that I have ever encountered (aircraft and lightweight railroad passenger cars) has a very distinctive look as seen above and is nothing like the examples of original green interior paint that I have encountered in wood railroad cars (all of which seems to be an oil based enamel)
Jason Midyette
Edited 1 time(s). Last edit at 05/22/2020 07:46PM by Jason Midyette.