# Why is stainless steel a poor conductor of electricity?

I recently had a metal plate put in my shoulder and was wondering why stainless steel isn't a good conductor (At least I hope it isn't). Does the alloy just lack free electrons? Why is that?

• It is a poor conductor relative to copper. I would not advise you to touch a live wire with it: it is a very good conductor in that case. Stainless steel is used in body surgery for its strength and its nor corrosive qualities. After all the body itself is a conductor epb.apogee.net/foe/fshrrh.asp . – anna v Jan 9 '14 at 8:21
• So how similar is the conductivity of stainless steel to the innards of the body? Are Eddy currents something I should be concerned about? – user24082 Jan 10 '14 at 2:10
• I think the body has some hundreds or thousands of ohms. Like any metal part in the body, you will not be able to pass detectors in airports, for example. Currents will be set up but it will not be dangerous, imo, if it is in the shoulder or pelvis or some thing neutral for the basic body functions. – anna v Jan 10 '14 at 4:25
• It's a collar bone support-Would you think it would be worth going through surgery again to get it out? – user24082 Jan 10 '14 at 5:23
• I really do not know. There are people going around with metal plates on their skull. I am sure if there were a danger you would have been warned, but you could ask your doctor. – anna v Jan 10 '14 at 5:56

You are correct, stainless steel is a really poor conductor compared to most metals. This source lists it as $7.496 \times 10^{-7}\: \mathrm{\Omega \cdot m}$ which is more than 40 times worse than copper.

The reason is that conductivity in metals is high is that metals form a crystal lattice where the outer shell electrons are shared and easily move through the lattice. When the lattice has imperfections the flow of electrons is retarded. Stainless steel is an alloy of iron with up to about 25% chromium (and sometimes a small amount of nickel or carbon) added for corrosion resistance. The chromium atoms disrupt the regular iron lattice and increase the chances of inelastic collisions with moving electrons.

• Brandon, that seems a bit qualitative. Your saying the conductivity is low because the electron mobility is low, which is a bit of a tautology. It would be nice to see evidence from e.g. microscopy for exactly how the crystal doimain structure is scattering electrons, and maybe contrast that with pure iron. I speak as someone who doesn't know the answer to this question! – John Rennie Jan 9 '14 at 8:22
• @JohnRennie yeah I was looking for more details of the crystal lattice of stainless steel but so far I haven't been able to find anything. – Brandon Enright Jan 9 '14 at 8:23
• There is some discussion of the crystal structure here: keytometals.com/… There is more information about the Austenite structure of stainless steel at en.wikipedia.org/wiki/Austenite but details are thin on why the austenite crystal structure is a poor conductor. Interestingly, it also isn't ferromagnetic. – Brandon Enright Jan 9 '14 at 8:33
• But as Anna commented, it's still more than good enough a connector to zap you. – Carl Witthoft Jan 9 '14 at 12:40
• @JohnRennie FYI, the reason stainless steel is a bad conductor is precisely because the electron mobility is reduced. This is not a tautology at all, but rather something that is taught in solid state physics courses. The scattering of the electrons is caused by the alloying elements, decreasing the time between collisions. See: en.wikipedia.org/wiki/Drude_model (also the first Chapter in Ashcroft and Mermin), also alloy scattering in thermoelectrics is the same mechanism: en.wikipedia.org/wiki/Electron_mobility#Alloy_scattering – mikeagibson Mar 24 '16 at 1:01

Stainless steel is a relatively good conductor of electricity, as are all metals. The body is also a good conductor, due to water. The skin is a relatively poor conductor of electricity because of dead skin cells. Any break in the skin, i.e. cut, greatly reduces its resistance.

• This doesn't really address the question of why it is a good conductor. – HDE 226868 Apr 12 '15 at 22:04
• Pure water is not a good conductor. Electrolyte solutions are good conductors because of the solute (salt, etc) , not the solvent (water). – Bill N Jan 5 '17 at 22:05