I bought an old unopened Bachmann CSX Dash 8-40cw DC at a flea market last summer. I was planning to convert it to DCC with sound during this winter. When opening her up, I noticed a bright green corrosion like you find on corroded copper battery cables. I did a lot of sound decoders conversion on my fleet of DC locomotives and they were all made from aluminum or magnesuim alloy. However, this one looks like its made of copper because of the color of the bare frame when I scraped off the corrosion. I'm planning to cut/grind the frame to fit a speaker. After the cutting and the grinding, I will spray paint the frame. My question why copper? When did they change over to the other alloy? Can I cut copper? I never cut or grinded anything copper before.
I don't think they were copper, but they may have been a copper containing alloy. the ontact strips were phosphor bronze on many locos.
My gut tells me that-considering the price of copper and the price of scrap-that your frame was more then likely a "zamac" casting. This alloy is similar to the old linotype material that typesetters used in the newspaper industry. It is a bit on the hefty side, has great resolution properties, and is easily reuseable by re-melting on-site and re-casting. I could be wrong, stranger things have happened.
SGT C.
type metal was lead, tin and antimony. there was no copper in it.
I don't believe that Rich is saying there is; in fact, just the opposite. What tells me this? His first line about "considering the price of copper..." And then going on to speculate, probably correctly, that something other than copper like ZAMAC, was used instead.
Zamak is a zinc and aluminum alloy that contains some copper, and trace elements of some other things. So it's possible the green film is from the copper in the Zamak if the loco was stored in a damp area for an extended time. A green "Scotch Brite" should take it off, and a coat of buffed bee's wax keep it from coming back.
Len
Bees wax has lots of uses.
How much, percentage wise, of copper are we talking about?
Anywhere from 1% to 3%, depending on which of the five classes of Zamak (Z2, Z3, Z4, Z5, Z7) it acually is. Since there's enough copper to cause the green film, this chassis is probably in the 3% range.
Len
Interesting. Never would have thought. Never saw green film on that kind of metal. Wonder if the OP's loco was stored somewhere really humid, which would not be a good thing for many other components of the loco. Thanks for the info.
I suspect your right about the loco being stored in a damp, or at least humid, location for some period of time.
I learned about Zamak when I worked at a marina during summer breaks when I was a kid in high school. These days, they're mostly stainless steel, but back in the day a lot of boat fittings were nickle and chrome plated Zamak castings. If the plating got worn away, they would get that green fuzz on them from being exposed to spray and humidity.
Len
that's very interesting. I'd never heard of Zamak before.
I think you'll find that the frames were not in fact Zamak, but more likely were made from a material called Pot Metal.
http://en.wikipedia.org/wiki/Pot_metal (http://en.wikipedia.org/wiki/Pot_metal)
Zamak was a trade name and held to a standard with quite a low percentage of copper in it. Pot Metal on the other hand was much looser in it's recipe and contained quite a significant amount of copper. Most old cheap castings I've ever run across, be it hobby, auto, marine, motorcycle whatever.....were plain old pot metal. Besides....Pot Metal was way cheaper than Zamak....guess which one got used more?
Sid
I always thought Athearn frames as least were made of pot metal. As I kid, I had a lot of small scale metal WW II planes. For some reason I thought those were Zamak.
I did Rich! And I as rooting for the COLTS. Saturday I was rooting for the RAVENS, so I hope when the COLTS come to town, they knock Brady on his a$$ and send that sour puss Belichek home!! Time to give the new kid, Luck, his shot at the title.
Jim;
Yep; Luck is pretty good, and did some noteworthy stuff last night. That game was kind of frustrating. I am a New England fan ( of course), but I hold no animosity towards any other team-to get where they are, that all have to be good.
I picked up several of my locos this weekend to take a look at the frames, and it looks just like the stuff the newspapers use for type. I worked at the Hartford Courant long ago for a short time, in the electrical dept, and it was there that I picked up a lot of knowledge about motor controls-and of course this is applied to this hobby.
As far as the copper in zamac, I have to go with the "experts". Another bit of knowledge gained.
Rich
(SGT C).
Strictly speaking, Zamak and 'Pot/White Metal' are both zinc alloys.
The difference is, Zamak has set standards for the percentage of other metals alloyed with the zinc. This allows control of density, brittleness, machinability, etc.
'Pot Metal' is just that. Whatever's handy gets thrown in the melting pot with zinc, and you get what you get without any quality control.
And yes, GO COLTS, GO!
Len
Hi, Len;
Yeah...FOR NOW...
SGT.C
The big issue with Zamak was/is the possibility of lead contamination. Any trace of lead in the mix will eventually lead to internal corrosion and eventual failure of the metal. Some of the early cast metal kit manufacturers, especially John English, had problems with this. There is no way to counteract the process. The piece will just crumble away.
The old white metal disease is what brought Central Valley to its
knees. Many trucks just fell apart. However those which have managed
to survive 'til now seem to be solid.
-- D
Don; with reference to Central Valley:
With their line of track, tie/switch strips, and rail (which can be bought several places; plus their tech assist, I hope they continue the upward trend they are on. Jack was truly a pioneer along the likes of Gordon Varney, Bill Walthers, etc. I am going to use their tie strip, code 70 rail and switch modules in my yards and servicing areas. It definitely has some advantages. Not to sound snooty, but it is my opinion [that] this product is not for new-bees or those with a light approach to this hobby. Their passenger trucks were non-parielle" (sp?) in this business; especially his side frames.
SGT C.
Len-
Zamac comes in a large array of recipes so it can look like many different metals. All of them, however, have similar
electrical and physical properties.
-- D