I found out about this paint while researching these specific CNW cars, so I don't know if this product was used elsewhere. 

I looked up 'galvanized paint' and it seems it is comprised of zinc powder, binders, etc. The process of applying it is sometimes referred to as Cold Galvanizing. Apparently this stuff was invented to repair the worn or missing galvanized coating on metal surfaces, so it seems reasonable that it would find uses in rebuilding, repainting, and other repair work. But I don't know of any evidence. Possibly shop records might show its use, but that's another research project!