Just disassempling a brass model LIRR 2-8-0 camelback and the boiler weight was covered in a white powdery substance. Have not experienced this before, so my questions are:
What is it? Is it a problem? How to remove it? How to prevent it?
Jim
It is a form of 'separation' of unlike metals. The weight material is most likely a metallurgic mess...I mean, a mix...yeah, a mix....of metals that weren't meant to be used the way they were messed...I mean mixed. Oh heck, you know what I mean.
I believe it is akin to 'zinkpest', the dreaded condition that so many of us find inside earlier boiler shells and on frames of locomotives. I have a Trix GG1 from 2002 that is beginning to show spots here and there on the frame.
There is no cure. If it bothers you, abrade away what you can see, but it won't last and it won't probably do the trick even if you grind a lot of it away. It'll still be all through the material. You just see what is exposed on the surfaces.
Sorry.
I suppose there is a chance the white power (assuming the locomotive was not being used to smuggle controlled substances into the country) MIGHT be what is left from a prior use of Brasso to clean the locomotive. It can leave a white powder when it dries
But if the interior weight has some zinc in it and is starting to show signs of zinc rot or zinc pest, I'd remove and replace it. I don't know how "catching" zinc pest is, but I do know that at least on some brass locomotives the driver centers were zinc allow castings and you'd rather not see them "catch" the dreaded pest.
Dave Nelson
Update - white vinegar disolves it.
I believe zinc pest is a galvanic reaction between the zinc and lead contamination in the zinc.
If the shell is zinc and the weight is lead it could be a similar reaction. Putting some sort of barrier (thin piece of plastic or a coat of paint) between them could help.
Or it could be brasso or similar contaminant/remnant in which case this wouldn't matter.
I give my boiler weights several coats of any clear lacquer or varnish. Sometimes they have a little white residue and I simply brush this off with a fine brass brush.
Some of the weights are cast in a more "silvery" looking metal, maybe more antimony, pewter, less zinc?. I rarely see these corrode. After twenty years or so on some of these engines I don't see any further corrosion after the clear coat.
Regards, Ed