Removing silver tarnish

[TimFox]

I did a quick search of the forum, and found discussions of silver tarnish (and other metals), but could not find a recommendation for removal.
I have some ancient military-style BNC connectors with badly tarnished silver plating.
I tried "Wright's Silver Cream", which my wife uses on normal silverware, but with incomplete results.
Has anyone had success with a commercial silver-tarnish removal product?

[Swake]

With that silver tarnish do you mean the black looking oxidation on the 'outside' of the BNC connector? If so it is just an esthetics issue not functional one. The connection itself is the copper/gold colored center pin and the ring you can see inside the connector.
In short: don't bother unless you really want it shiny but make sure not to contaminate the pin and ring.

[DaJMasta]

I'm also on the side of "don't bother" as the tarnish is only surface level and the top layer being tarnished protects the layer immediately under it - more like aluminum oxide than rust or something that can actually penetrate through.  Should you still want to, there are a huge number of silver and metal polishes that could work, and there are some that are fully liquid and you just dip the silver item into (for jewelry) that would probably do a complete job.  There are also silver polishing cloths that have a small amount of the tarnish removing chemical impregnated into a fine cloth, and these can work well (and probably leave less residue), but will probably struggle to remove it all from crevasses.

Even though with a BNC it shouldn't matter much, every polishing cycle is actually removing the top layer of silver, so for high frequency/close tolerance work it's probably not a good idea.  It's also just going to tarnish again - it's reacting with sulfur compounds in the air, so really the only way to prevent it is to completely seal it or fill it with a different atmosphere.  You'll find on old silver RF parts sometimes that when you undo a connection, the interior is totally bright and untarnished even when the exterior is a grey-black.  That also means that storing silver connectors in a bag will tarnish slower than in the open air and including something to pull those sulfur compounds out of the air would further prolong their untarnished life (I think silver polishing cloths do this?)

[rhodges]

The previous comment was probably your best.

But if it helps, some decades ago there was a liquid called "Tarn-X" and it really did work. But the silver would tarnish again quickly. Maybe you could re-invent the recipe for that formula and then clean the contacts...

[Swake]

Will add to this that the silver layer is exactly this: a very thin layer of silver on top of copper, which can itself be a very thin layer on top of some other metal that forms the connector. It actually doesn't take all that much force to remove the silver from the connector ending up even worse looking.

[Haenk]

i find that last method pretty promising as it is 2-in-1:
https://www.thekitchn.com/best-method-clean-tarnished-silverware-23228658

Might not be ideal for installed parts

However I find it likely, that the plating is not pure silver, but maybe contains a larger part Cadmium, not sure how good this will work.

[Doctorandus_P]

Silver oxide is conductive too, so there is no need to clean or remove it, and because the layer is thin, you are better off leaving it alone.

[TimFox]

In modern environments, the normal silver tarnish is a sulfide from atmospheric sulfur:  I'm not sure how conductive that is.

[crerus75]

Tarn-X is still available.  I remember that Jim Yanik recommended it for silver-plated contacts on older Tek scopes.
If you end up removing some of the silver layer and the substrate is copper, you can use Cool Amp powder to restore a thin layer of silver.  I've used it on switch contacts before (though not for scopes) and find that it works as advertised.  Expensive, but a small amount lasts a long time.

https://www.cool-amp.com/cool-amp?_vsrefdom=adwords&gclid=CjwKCAjwvrOpBhBdEiwAR58-3Jq0lYApJYof--BVE8ynFMm0EiQeHUqgsiX5IL7ZJi77OqFuIW6pZxoCXMQQAvD_BwE

[donlisms]

Caswell Plating has a moderately cheap silver brush plating kit.

For cleaning, there is the electrolysis technique with the aluminum and baking soda and all that jazz. This intrigues me. 

[cruff]

In modern environments, the normal silver tarnish is a sulfide from atmospheric sulfur:  I'm not sure how conductive that is.

Apparently it becomes conductive above about 177 ºC.

[coppercone2]

Well tarn-x will leave it looking crappy but it should strip the contaminants.

You need to re seal it with something like deoxit after wards to keep it looking fresh.

If you use it, do 30 second intervals. Pull it out and inspect. When it looks uniformly matte without the black, its done. A pre-soak in tarn-x before using polishing cream might result in less work.. but the polishing cream will def leave a nicer finish.

The only realistic solution for polishing this stuff is electropolishing. If something has a thick silver plating it might work.

You can also electroclean silver and gold. I have done a gold test fixture recently with electrocleaning, it did end up looking alot nicer. Its cheap. Polishing on precious metals I have not tried because platings are often very thin, they are not making it jewelry grade for everyday wear.

Think about it like alien. Tarn-x gets rid of the alien but the structural damage it caused is still there, its like mechanical damage. A light electropolish might get rid of some asparaties near the craters left by heavy oxidation. But its not gonna work miracles.

Chemical polishing is a thing though, for instance with TIG electrodes. If you dip a tungsten rod into a molten sodium nitrite salt, it will leave it as a nicely rounded blunt tip. That is good to keep in mind when you think about what chemical polishing and machining does.

With advanced electronic/fluidic controls, you can do things like remove burrs specifically, or even do surface polishing while leaving edge geometry in tact (i.e. endmill processing) but its damn hard to figure out how to do any of this.


And what you really want, is electroplasma polishing. That process does what people expect electrochemical polishing to do. But its rather power hungry and dangerous and not much info is available about it.

The problem is current density. You will never get it nice. Electroplasma polishing solves this problem by basically creating plasma around the entire part like a envelope, and the current density in this region is rather uniform from what I understand.

TO get anywhere near similar results conventionally on something complex like a BNC, you would need to get a little electrode on a multi axis positioner, and basically "machine" the object while under water, moving the electrode around as polishing progresses. Damn hard. For attempting plasma electrolytic polishing, you need something between 0.2 to 1 amp per square cm. So like a BNC connector is a Kw+ precision adjustable HV power supply.


TLDR: anything cosmetic on complicated shapes is damn hard, especially like the interior of connectors. A quick electroclean, tarn-x dip, electropolish, etc... should improve surface condition but it won't look new by any means. Mechanical polishing using small tools with creams and abrasives can result in a nice surface, if you don't mind a ton of annoying work, and the object has a thick plating.

What I go for on BNC (when to stop working):
1) exterior looks nice
2) feels smooth to plug in a cable
3) no visible bumps of corrosion (protrusions)
4) deoxit seal

[IanB]

For anything delicate with thin plating, I would recommend "Silvo":

https://www.amazon.com/Reckitt-Silvo-Tarnish-Guard-Wadding/dp/B0042LCEZM

There is an equivalent product for brass and copper called "Brasso".

For metal surfaces that really need a good clean, including mild rust, I would recommend Autosol:

https://www.amazon.com/Autosol-Metal-Polish-Chrome-Copper/dp/B003PHLTOG

I was introduced to Autosol as a child, and it is pretty much a miracle polish. It doesn't matter how badly oxidized the metal surface is, it will come back shiny.

[Bud]

Thin plating? Delicate? What you guys are talking about? I've cleaned RF connectors with TarnX and other polishing solutions and never came close to wearing the plating off.

[pickle9000]

Glass cooktop cleaner, it is abrasive, liquid paraffin to keep shiny. 

[pqass]

Assuming the connectors are loose...

[coppercone2]

Thin plating? Delicate? What you guys are talking about? I've cleaned RF connectors with TarnX and other polishing solutions and never came close to wearing the plating off.

and I have seen plenty of brass spots start to show up on cleaned connectors!

sometimes they look fine but under magnification with a light you see things!
tarn-x is fairly mild and safe as far as cleaners go, just don't expect it shiny

the center pin is where you see the most wear and the silver thins out first

[p.larner]

i dip my tarnished bits in concentrated zinc chloride then rinse off with water,no probs so far.

[jchw4]

From  https://www.ebay.com/itm/266460535081 .

[Swake]

Rest of that machine is in the same state. And yet they dare asking 299$ for this. OK, they mention it is for parts only, but in this case there is not going to be many good parts.

[jchw4]

The OP did not present any pictures, so it was safe to assume that they asked about something like the image above 

Rest of that machine is in the same state. And yet they dare asking 299$ for this. OK, they mention it is for parts only, but in this case there is not going to be many good parts.

It was "Free worldwide delivery"! So I guess that the owner clearly knew the real value for that. Assuming $150 delivery, it was $150 for a few screws and side panels.

No, I did not buy it. I just wonder how a very nice signal generator could get into that state. 

I feel that some ebay sellers should offer negative price for their scrap.

[Haenk]

awful, either it took many years of humid storage, or corrosive environment
I guess there is not one good part in it

[TimFox]

No, my old BNCs are not so bad as those.

[Paceguy]

As others have stated, don't use anything abrasive to avoid removing any of the silver plating. I use an ultrasonic cleaner to clean my silver plated connectors that I pick up used here and there. I removes some of the oxidization but mainly dirt and grease. This has worked well for me so far.

[jchw4]

As others have stated, don't use anything abrasive to avoid removing any of the silver plating. I use an ultrasonic cleaner to clean my silver plated connectors that I pick up used here and there. I removes some of the oxidization but mainly dirt and grease. This has worked well for me so far.

Could you share your ultrasonic bath recipe to clean the connectors?

Most of the recommended stuff is water-based. How do you make sure there is no remaining water in the attached cables, or inside the connectors?

Or do you use alcogol-based solution? Which is kind of potentially flammable and scary.