Is the skin depth of tarnished silver any different than untarnished?

[cmb]

TL;DR

Is the skin depth of tarnished silver any different than untarnished?

That's it, just the question.

I am figuring that the tarnish is an irrelevance as it does not participate either magnetically or electrically, so any RF current passing through the [still metallic] silver top layer, albeit with tarnish over the top, will pass through the same thickness of metallic silver and the skin depth magnetic fields will penetrate to the same depth as in the metallic case.

I'm assuming 'normal' tarnishing here of the type one gets leaving something lying around a domestic situation, silver sulphur compounds usually I think.

Therefore, so long as there are good surface-clean metal to make contacts with such a piece, then passing an RF current through the contacts, will be exactly the same as if there was no tarnish between those cleaned contact areas.

Is that about it? Any subtleties I am missing here?

 

[Baluncore]

Any subtleties I am missing here?

The skin depth in the silver metal will be the same.

But the tarnish is a dielectric, that may also absorbs moisture, and so increase dielectric losses, and very slightly slow the velocity factor over the tarnished surface.

The metal oxides and sulphide compounds that form a tarnish may be semiconductors that can increase resistive losses, and possibly generate some harmonics or cross modulation with low level signals.

 

[cmb]

Good points.

 

[bobob]

Yes, it is. That is why a very thin layer of gold is usually flashed over the silver in waveguides.

 

[Baluncore]

That is why a very thin layer of gold is usually flashed over the silver in waveguides.

Silver is the best conductor, followed by copper, then gold.
But silver and copper tarnish, while gold does not.

Waveguides for high power employ a silver plated copper base, but with a positive pressure dry nitrogen fill, to reduce surface tarnish of the silver and associated losses.

Microwave instruments maintain their calibration over longer periods if waveguides are internally plated with gold.

Some waveguides are copper based, with the inner surface silver plated, then flashed with either rhodium or gold to reduce tarnishing of the silver.

 

[tech99]

I have noticed that if there is a thin insulating oxide layer between metals in loose contact, we seem to get electron tunneling, which gives a non linear but bi-directional action. It does not seem necessary to have a semiconductor for non linear action.

 

[Baluncore]

It does not seem necessary to have a semiconductor for non linear action.

I would call a tunneling contact a semiconductor.
Plating is not a “lose contact”, it forms an alloy of two conductive metals at a junction, parallel with the current flow.

For low power and voltages, semiconductors appear to be insulators. For higher powers and voltages, any semiconductor is fused or vaporised.

To cause non-linearity problems, the unintended semiconductor needs to survive in a junction, as part of a circuit, rather than as a grain of material resting just above the surface alternating current, swept by the guided alternating magnetic field.