I was given a 50-60 year old Bowser HO Brill Trolley, #1-125220, in its original box. It has an excellent well detailed cast metal body that has never been touched, still has all the casting flash. It has a large (by today's standards) five-pole permanent magnet motor that runs well, once I brightened the brass wheels and removed rust from the steel axles to get current flowing. It even has all the parts to convert to hot wire operation. The price on the box is $44.95, a healthy bit of money back when I was making about $1.25 an hour. My problem is how do you prep a cast metal body for painting. I assume the casting is either a zinc alloy or pot metal. My first instinct is 91% alcohol bath, but that might not remove the mold parting compound that was used 50-60 years ago. Would soaking in hot soapy water work? Also, should I use a primer on the metal before air brushing with acrylics? What type of primer? Thanks for any insight.
Hopefully the metal is still in good shape. Sometimes the older zinc (Zamac?) castings would sort of rot after many years. I think an initial wash in detergent and warm water, scrubbing with a soft toothbrush, would be a good start. With the last Bowser kits I built about 10-12 years ago, the recommendation was to soak them in white vinegar for 15 minutes or so to put a slight bit of etching on the metal's surface. But.... before doing a vinegar soak take a good look at the metal for the aforementioned zinc rot. If the metal is not totally sound and somewhat shiny with no trace of white-ish coloring on it then avoid the vinegar as it could make the rot worse. My kits were purchased new direct from Bowser. George V.
Zamak is the pest-free zinc so it won’t get rot. Anything made 1960’s and after is fine. I don’t work too much with metal kits, but I agree with the vinegar. I would also recommend a primer. I have heard that spray can paints like Krylon or Rustoleum work fine. I haven’t used them on any of my airbrushed models so I can’t say for sure. If it is an enamel or a lacquer under an acrylic I would avoid that. The oils evaporating underneath will destroy the acrylic on top. I have used Tamiya paints with great results. The sky grey color is a good primer, although they are expensive for a tiny bottle. I usually cheap out and don’t use a primer, and the small metal parts I have worked with seem fine. For a larger piece I might still prime it, so I guess it is up to you.
Most of my experience with painting metal was with led miniatures. Although I was always told to prime, I rarely did. I would use whatever paints were at hand, but found humbrol oil based paints to be the best paint. I had some minis I later sold on ebay, they were easily over 25 years old and the paint stood up great. So yeah, I'd go humbrols right out of the can.
Thanks. I had forgotten about Zamak. I believe that Bowser, Mantua, Penn Line, Varney all used it for their castings. So maybe I should be OK with a primer after a good soap and hot water bath, followed by vinegar. The metal looks and feels sound. Though I may have to go 50 miles away to find a primer. I have only Hobby Lobby for paints locally.
Actually, the age of the Zamak is not the important factor. It is the formula. Too much of certain impurities will cause the deterioration. If they got it right, it will last indefinitely. And yes, Zamak IS susceptible to the "rot". It is the type of alloy usually referred to when the "rot" is discussed. Some very recent N scale loco fame castings have exhibited "rot" (I call it Zamakitis). If the casting is still good after 50-60 years, it's good period. If no warping or brittleness is present, it's a good casting. Primer is desirable if the final coat is not self-priming. Primer adheres much better to bare metal and the top coat adheres well to the primer. Baking also contributes to a tough finish. Primer made a big difference with my Treble-O-Lectric castings with a baked on finish virtually unchippable. Doug
