# Muriatic Acid for Ferrous Base Metals on Contacts



## Fever (Feb 17, 2011)

Gents,

I have searched for answers to this question to no avail, and I'm asking for some help. I recently acquired a good amount of silver contacts from some retired factory machinery. Most of the contacts appear to be 90% or greater pure silver (also checked with acid etch). Probably what is called "Coin Silver" I believe. Most of these contacts are soldered to copper, but there are some that are soldered to a magnetic base metal buss. I'm assuming these could be Nickel, but I think they are excessively magnetic to be anything but an alloy of Iron and other elements. I have heard of "Heusler Alloys" which are composed of Copper, Manganese, and Tin, and which achieve varying magnetic properties based on its heat treatment. I probably don't have something this exotic, so I'm assuming some other combination or alloy.

As per the picture, I snipped some of these smaller contacts from their magnetic busses, and added them to a flask with 31.45% Muriatic Acid. The reaction is less than extraordinary, and mildly bubbles. This has been allowed to continue for several days, and it appears the reaction is slowing down. Yet, there remains the same magnetic busses attached to the contacts. I can confirm that the contacts themselves are NOT magnetic- only the base metal to which it is soldered.

My goal is to dissolve these base metals in hopes of liberating the Silver contacts, at which point I can move to the process of incineration and later chemical recovery and refining.

So, is store-bought Muriatic Acid too weak to sufficiently dissolve ferrous components from contacts? What would be a good alternative without creating sulfides or other protective oxidized layers?

Thanks for any recommendations in advance....

Fever


----------



## Barren Realms 007 (Feb 17, 2011)

Possibly tungesten(sp).


----------



## lazersteve (Feb 17, 2011)

Have you tried to sweat the contacts off with heat?

Steve


----------



## dtectr (Feb 17, 2011)

Damn!
BUY GOLDSILVERPRO's book which discusses "How To Process Silver Contact Points ...[page] 93"


----------



## Fever (Feb 17, 2011)

Steve- Sweating them off with my torch is an obvious solution, except for the fact that I have probably 1000 of these in a bucket. That's a lot of sweating! So I though an easier step would be to chemically liberate the contacts form the base metals. Since I trimmed the contacts super close mechanically with a snips, I really wouldn't be going nuts with large amounts of acids.

BR- I have never heard of Tungsten buss bars. I think you may be referring to Tungsten/Silver contacts, which these definitely are not.

As for GSP's book, I'm on my way! Thanks!

Fever


----------



## Barren Realms 007 (Feb 17, 2011)

Yep I was, cool no problem.


----------



## Palladium (Feb 18, 2011)

Drop one in some warm H2O2 and see if you get a reaction.


----------



## johnny309 (Feb 18, 2011)

YOUR muriatic acid is strong enough...assuming that the best is 32%....you'll never find much stronger than that.
Second...yes,it is cheap....because it is a secondary reaction of production of NaOH used in the manufacturing of soaps,detergents....
Pardon my poor english,but I haven't had the time to practice.


----------



## dtectr (Feb 18, 2011)

The suggestions that follow are pretty crude & basic, but may be worth a shot on small samples for general learning purposes:
Dilute muriatic attacks many base metals much faster than concentrated. Maybe put 1 item in a vessel with dilute HCl & another with dilute sulfuric. Concentrated sulfuric will work as a Nitric substitute, dissolving the silver, (but probably most of the base metals, as well) as long as the copper content is below 8%.
You can do a "spark" test on the metal before treatment - touch it to grinding wheel & if steel you'll get a spark, from the carbon alloy. This is a very crude test, but very accurate as well.
Just some random ideas ...


----------



## Fever (Feb 22, 2011)

Great suggestions guys, thanks.

The more I think about it, these small busses are probably some Stainless alloy, which would explain why the reaction is so slow. After 12 days in the HCL solution with minor H liberation, the busses show signs of attack, but have not dissolved.

Curious as to the suggestion of using warm Peroxide- What kind of reaction are you hypothesizing? If a reaction occurs, what metals would this indicate? Thanks for your help!

Fever


----------



## seawolf (Feb 22, 2011)

What about a dilute nitric and precipitate the silver.
mark


----------



## Fever (Feb 22, 2011)

seawolf-

Yes, Nitric would definitely do the trick, but I was trying to save that for just the actual Silver discs, after digesting the iron containing busses to which they are attached in a cheaper solution (HCL). If all else fails, I will proceed to the Nitric step and cement with Copper.

Fever


----------



## nickvc (Feb 23, 2011)

Fever said:


> Great suggestions guys, thanks.
> 
> The more I think about it, these small busses are probably some Stainless alloy, which would explain why the reaction is so slow. After 12 days in the HCL solution with minor H liberation, the busses show signs of attack, but have not dissolved.
> 
> ...



Fever if it's stainless try heating your Hcl this should work much faster and with luck it might liberate your contacts without the need to dissolve all the base metal, take out a sample and see if the contact can be pushed out once the reaction really gets going.


----------



## Lonnie (Feb 23, 2011)

Fever 

Why not just torch them off it's simple and very fast ? They melt like a crayon in just a second and will roll off right into a pan of water . When I do the small ones like those I get a thick piece of metal and line them up on it just as close as you can get them . 

Then start at one end melting them off and into a pan of water . Takes some time to line them up but I'm certain I can remove 6 troy ounces an hour . I've never posted a pic here but if this works this is 5.5 ounce of the same contacts done this very way . It might have took me an hour to do this . 







Well it did work 

Edited to say not all of these were melted off . But if they small and a pain thats how they get removed .


----------



## jimdoc (Feb 23, 2011)

How do you know that there wasn't any cadmium in those contacts?
Most refiners don't take silver contacts for a reason.

Jim


----------



## Oz (Feb 23, 2011)

jimdoc said:


> How do you know that there wasn't any cadmium in those contacts?
> Most refiners don't take silver contacts for a reason.


Just as a reminder to everyone. Cadmium goes into nitric acid very easily and is often used as part of the alloy in silver electrical contacts. 

So if any of you are digesting contacts in nitric for the silver content you must cement your silver on copper in order to separate it from the cadmium. Wash very well to be sure all cadmium bearing solution has been removed from your cemented silver. Cadmium is nasty stuff, and Jim is right that most silver refiners reject silver if it has cadmium or have penalties for its presence.


----------



## Lonnie (Feb 23, 2011)

Well all my contacts were shot with a hand held scanner by the owner of Nobel metals in Oakridge Tenn . But your right I dont know that about his contacts so scratch that idea of mine . As for myself I have every ounce of material in jugs from things I have done . Every filter paper every ounce of rinse water everything saved in jugs . 

I concentrate wash water and planned to nutralize any acid if I ever got shead of it . To be honest I hadn;'t thought about that and had planned to take my stuff ( it has value in it ) and give it to the people at Heraeaus . If they wasn't interested in it I figured to get shead on no questions asked day .


----------



## Fever (Feb 23, 2011)

Thanks for the tip Lonnie,

Never thought of completely melting them and catching them in water. Seems like a great idea. My only caution would be the fumes, especially if Cadmium is present in any of my contacts. I just might look into a specific respirator that filters out Cadmium fume, or metal fumes in general, and start melting all of my contacts as you suggest. I certainly will not do this until I am 100% sure I can protect myself from the melt fumes. Even the smallest colloids of toxic metals can be very detrimental when inhaled.

Thanks again,

Fever


----------



## Fever (Feb 23, 2011)

Upon second thought, due to the unnecessary risk, I think I'll stick with my plans to digest in Nitric, and cement with Copper.


----------

