While it might be an interesting science project, my ypothesis is that the oxidation due to humidity air born polutants, etc. would be so much greater that any difference due to the current being carried would not make any practical difference.
On the other hand, one of the very first command control seminars I went to (way back in 1984?) recommended brass track over nickel-silver due to the greater electrical conductivity. Of course we get around this by simply installing more feeders.
jwhitten I was reading along the "high price brass track on ebay" thread and had an interesting thought / question-- and am interested if anybody knows the answer... Regarding oxidation and electricity, or more specifically, "electrolysis"-- the two are electro-chemically linked. In a standard electrolysis setup, a direct current (i.e. "DC") is applied to an ionic material, which causes electrons to flow either toward or away from the material, respective of the polarity of the current. When a metal "oxidizes", it undegoes a transformation at its surface caused by a weak electrolytic / ionic reaction involving the oxygen in the air, and perhaps other trace elements which may be present. Over time, the constant action of the electrolytic condition causes the actual chemistry of the external surface of the metal to change. Depending on the specific type of metal, its apparent conductivity may also change. Now, here's where my thought / question comes from-- a layout which uses Direct Current ("DC") as its primary element of control, is probably more susceptible to oxidation due to its constant infusion of current through the rails, which would have a tendency to increase the rate of oxidation in the rails and wheels and other metallic elements involved in the flow of electricity to/from the throttle and motors. Theoretically a layout controlled by an Alternating Current would not be susceptible to any (much) increase in the rate of oxidation due to the tendency of the reversing currents to "cancel out" the effect in both directions. In other words, it would spend part of its time attracting electrons and part of its time repelling them, and theoretically the electrolytic effect would cancel itself out and thus the rate of oxidation would not be substantially affected one way or the other. (I don't know if that holds up in reality-- perhaps someone knows?) I am wondering whether the rate of oxidation in a layout controlled by DCC is essentially the same as would be present in a layout operated with Alternating Current? So in the case of brass track and DCC, does it oxidize faster? Slower? At about the same rate as with plain old direct current? Are there any differences? John
I was reading along the "high price brass track on ebay" thread and had an interesting thought / question-- and am interested if anybody knows the answer...
Regarding oxidation and electricity, or more specifically, "electrolysis"-- the two are electro-chemically linked. In a standard electrolysis setup, a direct current (i.e. "DC") is applied to an ionic material, which causes electrons to flow either toward or away from the material, respective of the polarity of the current. When a metal "oxidizes", it undegoes a transformation at its surface caused by a weak electrolytic / ionic reaction involving the oxygen in the air, and perhaps other trace elements which may be present. Over time, the constant action of the electrolytic condition causes the actual chemistry of the external surface of the metal to change. Depending on the specific type of metal, its apparent conductivity may also change.
Now, here's where my thought / question comes from-- a layout which uses Direct Current ("DC") as its primary element of control, is probably more susceptible to oxidation due to its constant infusion of current through the rails, which would have a tendency to increase the rate of oxidation in the rails and wheels and other metallic elements involved in the flow of electricity to/from the throttle and motors. Theoretically a layout controlled by an Alternating Current would not be susceptible to any (much) increase in the rate of oxidation due to the tendency of the reversing currents to "cancel out" the effect in both directions. In other words, it would spend part of its time attracting electrons and part of its time repelling them, and theoretically the electrolytic effect would cancel itself out and thus the rate of oxidation would not be substantially affected one way or the other. (I don't know if that holds up in reality-- perhaps someone knows?)
I am wondering whether the rate of oxidation in a layout controlled by DCC is essentially the same as would be present in a layout operated with Alternating Current?
So in the case of brass track and DCC, does it oxidize faster? Slower? At about the same rate as with plain old direct current? Are there any differences?
John
I'm coming from a marine and aviation electronics and maintenance background. In the marine world, ordinary oxidation is considered a different animal than galvanic (sometimes called electrolytic) corrosion.
Ordinary oxidation takes place through eposure to oxygen in the air. Oxidation is accelerated by temperature, humidity, and the presence of airborne salts. Using bare copper wire in indoor (layout bus) and outdoor applications (antennas and aerial power lines), I've never seen any difference in rate of oxidation based on current flow in the wire. Nor have any texts ever mentioned current as a factor in rate of oxidation. I would bet on temperature and atmospheric composition as much more important factors.
Oxidation can be retarded in a given environment by polishing and hardening the metal surface, and by coating the metal surface - paint, Wahl clipper oil, No-Ox, CRC 2-26, metal polish, etc. An example of polishing and hardening in the railroad world was Russian or planished iron for steam boiler jackets. Another example is the top of the steel rails that see frequent use. The coatings seek to prevent atmospheric oxygen from reaching the metal surface. The CRC (and to some extent the others) also displace any moisture present.
Galvanic corrosion requires the presence of 2 dissimilar metals with a somewhat conductive path between them. Wet wood or a film of salt water are generally good enough to get corrosion started between the 2 metals, with the less noble metal giving itself up. Galvanic corrosion is much more serious and results in much, much faster destruction of metal than oxidation.
Damage from galvinic corrosion is prevented by placing sacrificial pieces of metal (usually zinc) so that it is sacrificed instead of bolts, propeller shafts, etc. Another passive technique is to prevent the voltage difference from building by bonding each piece of metal to a common heavy gauge wire - sounds suspiciously like a bus/feeder wiring system! Voltage difference can accelerate galvanic corrosion, with current being the result of the voltage difference for a given resistance. Cathodic protection systems impose a reverse voltage in the local area (salt water immersion) to prevent aluminimum props and casings from being eaten by shafts and struts.
I have seen minute amounts of galvanic corrosion around the spike heads of my handlaid track in a non-air conditioned house in Southeast Florida. The steel spikes started to eat the nickel silver rail in a warm, moist, salt-laden environment. But I've never seen any evidence in a more normal environment.
The final avenue of corrosion/oxidation for track would be sparking/arcing. This is where the static potential between two metal surfaces can reach high enough levels to ionize the air between the surfaces, creating a spark. Dry air is needed to achieve this difference in potential. The sparks often result in a pitting of one metal surface as minute amounts of metal are heated and oxidized or melted by the spark. The same coatings used to prevent oxidation are often just conductive enough to prevent achievement of the static potential necessary to spark. Humid climates have less susceptability to sparking.
Back to the original question - the amount of time that significant current is actually flowing through the rails is pretty miniscule in the grand scheme of things. So even if DC current does accelerate oxidation noticeably, the difference would be negligible unless you operated around the clock for days on end.
OTOH, sparking is far more likely with the constant DCC voltage than with the lower voltage DC levels commonly used. And sparking, aside from oxidation, is far more disruptive to DCC operations than DC. I would submit that a very thin coating of some kind on the rails and/or gleaming is more useful on DCC layouts than on DC. Or just run your trains more frequently!
Probably far more than you wanted to know.
Fred W
A guy I've met out in Bowmanville has nothing but brass track for his layout. He told me that he uses Whal's clipper oil on the tracks to keep them clean.
I have some brass Shinohara switches that I plan on using on my current layout but in siding & yard duty. I plan on using this technique to keep the brass track clean.
Gordon
Brought to you by the letters C.P.R. as well as D&H!
K1a - all the way
Boy John, that was a lot of typing.
I have no idea about the correct answer. I never ran brass track when I was DC, I was new and I was told it was bad. I did not install any brass track till after I went DCC. As I have stated a few times, Ii have had no problems with the brass track staying as clean as my N/S track.
Ken
I hate Rust
Yeah, yeah, this post probably belongs in the DCC forum... so report it and make me move it :-)