03-23-2009, 09:12 PM
jim currie Wrote:a post in the wahl thread made me remember that i posted a researched ( as i couldn't find and hard facts in the controversy)thread in a brass rail versus nickle sliver in the old forum so here it is whit some updated info this is not to start a argument i hope just some facts. .
After this thread started I did a lot of research on the properties of both brass and nickel silver also known as German silver and come up with a ton of information so I tried to keep it as short as I could. But first the chemical composition of brass is copper and zinc the commonest alloy is 63% copper and 37% zinc nickel silver is copper zinc and nickel the common alloy is 65% copper 18% nickel and 17% zinc the conductivity of each base metal using silver as a rating of 100 copper comes in with a rating of 97.61 zinc at 29.57 nickel at 12.98 so it would stand to reason that nickel silver rail is not as good of a conductor as brass rail but we use such short runs of it that re stance is not factor.now as for the oxides the major component being copper in both brass and nickel silver the common black oxide we get on our track is called cupric oxide its conductive qualities I didn’t find a site that dealt with it(fore all the years of shuddering locos we all can guess on it), but did find that it is a toxic substance(new to me).nickel oxide is also black but being only 18% of the metal in the alloy that it will be found in smaller amounts (which is a good thing as it carries a cancer warning) as to the conductivity qualities if the base metal in of low conductivity of the oxide would stand to reason to be also lower. The zinc oxide is a whitish gray color is not toxic and harmless unless you ingest large amounts of it, but the fumes of zinc are deadly if breathed in confined spaces. The oxides from all three of these metals are used in the electronic industry from what I found mostly in the integrated circuit manufacturing. Also there I a myriad of other compounds that can be formed the such as sulfides which form in locations having sulfur compound fumes in the air .so from all I can find the only advantage to nickel silver track over brass is the appearance and that is why I only buy new track in nickel silver but use brass I have.
update information on this, the first solid state rectifiers were copper oxide, so the black copper oxide on our rails is a rectifier more or less
The problem with what you are saying is that the components of an alloy do not oxidize separately. The alloy has its own oxidation characteristics that may or may not be related to the characteristics of its component elements. An alloy's structure is a unique crystalline structure resulting from the bonding of the alloy elements. An alloy has the same composition throughout, unlike plated metals.
All brass alloys (brass is an alloy of copper and zinc) I have ever used oxidize very rapidly in humid climates. I know, I used to have polish brass daily on the ship I was assigned to. Polish the bell or the brass table, and the next morning it would be already be tarnishing. Polished brass also tarnishes fairly easily just from the oils in human fingers. The only long term fix I saw to brass oxidation was a clear lacquer coating - commonly used on military belt buckles and other ornamental brass (think door knobs and fixtures). Oxidation on brass rail will break down fairly easily by running trains frequently, which produces a polishing action. In HO, about 10 times around with a 10 car train with weighted cars and metal wheels twice a week would keep the oxidation at bay for me. Larger scales get better polishing action from running trains. This was in Northern Virginia with no air conditioning to dry things out in the summer (1960s).
Nickel is added to quite a few alloys to enhance corrosion (oxidation) resistance. Stainless steel and nickel silver are prime examples of the use of nickel to reduce oxidation. Nickel silver is considerably slower to oxidize than brass. But as you correctly state, nickel silver oxide is not much more of a conductor than graphite or other semi-conductors. It's just that steel (not stainless) and brass oxides are total non-conductors. Even polished nickel silver is not nearly the conductor brass is, and is even worse than steel. But at the distances the power travels through our rails, and given the cross section compared to typical copper wire, the extra resistance is not an issue. If you are running 5 amp loads through code 55 rail, you will probably need to put feeders in at closer intervals.
Nickel silver is the favorite material for rail because of its more realistic appearance, decent soldering qualities, and fewer problems from oxidation. Brass can be a satisfactory rail material in a reasonable environment, and when used frequently. But used occasionally in a humid or salt-laden climate, it's hell with keeping it clean enough for decent operation in the smaller scales. Some of my older locomotives have brass tender truck bolsters, side frames, and wheels. If one of these locomotives won't run well (smoothly at slow speed), it's invariably oxidation of the brass in the tender electrical pickup. It's lots of fun to clean that up.
And FWIW, the rail and driver tire materials do have a noticeable impact on traction. Nickel silver wheels on nickel silver rail - the most common combination these days - is actually the worst of the commonly used materials. Steel driver tires are the best, and are at their best on steel rail. Steel drivers and steel rail is seldom seen in model railroading because of modelers fear of rust - especially when stored. Custom locomotive builders used steel tires for the extra traction when their customers would allow it. Today, stainless steel alloys with reasonable machining qualities are used for driver tires in the very best locomotives. Some steel rail is still made - it's easier on the dies than nickel silver - but lead is added to the alloy to enhance soldering characteristics, and also prevents rust. The lead in the steel alloy has the disadvantage of taking away the silvery steel color, which has reduced its acceptance in the market place.
The above are all observed facts.
my experiences and research
Fred Wright
....modeling foggy coastal Oregon, where it's always 1900....
Chief Engineer, Mechanic, Wiper, and Jack of all Trades for the
Picture Gorge & Western Railway - none more picturesque!
Port Orford & Elk River Railway & Navigation Company - Home of the Tall Cedars