Non-Chemical Processing an Old Plating Basket

[The Refiner49er]

Hi All-

I have a small refining project that I wanted to throw out on the Forum and get a few opinions on the best way to handle this, it is an old electroplating basket from a defunct jewelry manufacturer. It is my understanding that the structure is copper construction and was used for nickel, silver and gold plating of various parts.





The two methods I am currently considering are:
1. Cut it into "bite size" pieces and run in nitric acid to remove as much base metals as possible, similar to refining gold filled items, then on to AR, probably twice to end up with clean Au powder.

2. Use a furnace process first, melt the total mass and pour cornflakes before going to #1 above, in the interest of creating a more digestable form.

Please provide any comments or suggestions, Thanks!

 

[4metals]

Back in the day when I was involved with electroplating I refined many baskets like these, the trouble is the layers of different plating can effectively seal off the layers below from nitric attack. I got around this by making the baskets of brass rod and mesh so the whole thing could be easily melted, corn-flaked and parted in nitric.

The baskets in use before I switched to brass were stainless rods and mesh so melting was not an option. Then I cut them into sheets which could lay flat and used the time honored refining technique of beating the crap out of them with a small 3 pound sledge to crack the layers so the nitric would penetrate. We had lots of nickel so it was quite brittle. Considering the heavy buildups we had of gold on the baskets it was worth doing. But the ability to melt the brass base made the overall process much simpler.

 

[The Refiner49er]

Thanks for your response, I am not adverse to getting a hand sledge out if necessary, probably a great "stress reliever" at best, LOL!

I don't have this basket in hand as yet but believe it is copper or brass in construction, note there are a few other pics that I didn't post that show the typical greenish oxide in places. I assume from your statements that the recovery may be respectable, unfortunately I do not know the specifics of the PMs that are built up, so it is probably anyone's guess.

Do you think if the proper force(s) were applied that the bulk of the coating material could be separated from the frame? If so, this may better avail a nitric process or at least reduce the volume to be melted or alternatively the amount of acid that may be required.

Thanks Again!

 

[4metals]

The yield depends on what they were plating. I always tried to keep gold and silver separate for recovery reasons. Mil spec gold plating usually had nickel under plate requirements so the deposit built up and was quite brittle. That made the sledge hammer more practical.

 

[Anonymous]

the trouble is the layers of different plating can effectively seal off the layers below from nitric attack.

If he dilluted his nitric well,and used a bubbler,or some other type of agitator,wouldn't that inhibit the passivation?

 

[4metals]

In the screens I processed, some of the layers were gold, which back in the mil spec gold plating days was thick. It wasn't a question of passivation, it was insolubility, the nitric would not eat through the gold.

 

[The Refiner49er]

Well, I am going to think positive here and go straight to melt, as this is probably the best way to deal with the various unknown layers. I always run material in dilute niric as the commercial grade (68%) is still plenty good at 1:1 or even less with water.

I was told there may even be Rhodium layers on this basket, but not sure if the relatively small and theorectical quantity would justify bothering with, especially since I have not worked with any Rh in the past.

Any further comments? Thanks!

 

[butcher]

I really do not know which way would be best, but for some reason my head say's if electrolysis put the metals on there, reverse electrolysis will take it off. (???)


I think before I melted, and poured if that was my choice, I would make sure those rods were not stainless steel.

Maybe hammer off what you can to separate that from bulk of base metals and treat the two separate, although the crust removed may also need in-quartering, silver could be added to it.

Very interesting find, do you mind me asking how you ran into this basket,

 

[nickvc]

I think before I melted, and poured if that was my choice, I would make sure those rods were not stainless steel.


Good catch Butcher, the same thought was going through my mind to.
Reverse plating to my mind would be a nightmare due to the multi metal layers and I'd go with 4metals suggestion, bashing the daylights out of the basket seems the right technical approach.

 

[Palladium]

I use to build furnaces for sweating aluminum off steel. I wonder if you could somehow heat the basket up and allow all the metals to run off. That is if it is stainless.

 

[nickvc]

My only worry would be that at the temperature needed any gold coming into contact with the stainless would migrate into it.
I still like the idea of the big hammer, stress relief and recovery of the values :mrgreen:

 

[The Refiner49er]

Thanks for all your viewpoints, I am fairly sure this basket structure is composed of copper or a copper based alloy, although I will not have possession of it until tomorrow. You might be surprised that I got this off eBay, normally it is difficult to purchase decent refining items at a reasonable price, but sometimes (infrequently) the bidding does not go very high; and this particular piece was odd enough to keep alot of the regular gold buyers out of the game.

In regards to the PM content, I am betting that there is a predominance of silver so inquartation would be a given in a melt/cornflakes process with nickel being the problematic component. At least there probably will not be any tin or solder to deal with, which I find to be a real pain in the A**. I am going to attempt a mechanical separation process to see what is present and run some of the fragments in nitric as an initial test.

Will let you all know how this goes, Thanks Again!

 

[publius]

Now that you have resolved the issue with how to proceed, I would like to relate a story about hammers...

While in the US Navy, I worked in the Hull Technician shop. We had a BFH that was a 20 pound sledgehammer with a 6 inch handle, known as "Junior." (BFH stands for Big Fine Hammer :roll: )

 

[The Refiner49er]

Well, the results are in, this plating basket yielded just short of 1/4 ozt of gold, virtually no silver and ALOT of black sludge after nitric digestion. Somewhat below expectations, but Au nontheless. I suppose the build up (obviously) has everything to do with the specific use during its lifespan, not complaining but the appearance was much better than the outcome.

Thanks for all the input!

 

[nickvc]

You say you had a lot of black sludge after the nitric....if this was used in the jewellery business could the sludge be rhodium? I would certainly test it to find out what it is or if it has any value.

 

[The Refiner49er]

I did not filter or attempt to separate the sludge from the fine gold particles, just rinsed it several times after running in nitric and added AR, it virtually all dissolved. I dropped the gold and have retained the remaining dark solution for testing, but have been busy the past few days so have not had time to research test methods for Rh. Any suggestions?

Thanks!

 

[nickvc]

I'll assume you have precipitated all the gold, tested with stannous, and would certainly be tempted to add a copper bar to see if any cementation occurred, if you do cement anything you have values.
Rhodium isn't keen on dissolving in AR but if fine enough and the solution is heated I'm sure some will dissolve. I'm no expert on PGMs but will collect them as a whole for melting and assaying so my advice might be off but certainly test your solution to en sure you don't have values in it.

 

[goldsilverpro]

For what it's worth, this link deals with similar material
http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=1415&hilit=media+nodules