HCL VS Nitric for removing base metals?

[Lady_Leprechaun]

Hi all, first post. I’ve been reading the forums for about a year as a guest but just recently joined. My first attempt at refining gold was a disaster, and I put that solution away until I learn how to deal with it. I am trying to get a handle on the recovery process before I attempt refining again. So my question at the moment is in regard to some GF watch bands I have. I am having the hardest time removing the steel by hand, so I am trying to decide what my best option would be from here.

I could do a hot HCL treatment to remove the steel and other base metals,but is this a crazy time-consuming process? Do I need to heat it, the stuff gets pretty hot on it’s own. But I’m not trying to wait days for it to finish dissolving the steel. I’ve seen AP is not the best option for GF, so that is why I am leaning toward hot HCL.

Or I go straight to hot Nitric and dissolve all base metals except the SS, but will having the steel in there mess up the process?

Apologies if this has already been discussed elsewhere on the forum. I did search first. Thanks for taking the time to read and respond!

 

[canedane]

You have a lot of base metal to desolve, maybe this will be a better idea. https://goldrefiningforum.com/phpBB3/viewtopic.php?f=37&t=28939
Henrik

 

[goldenchild]

If you can't remove the caps you may be better off just selling the scrap and get a different type. On average the caps make about 30% of the total weight of the band (mens and womens). The band itself is also stainless. It would take forever to dissolve in HCL and take a ton of it. And yes it would need to be hot. The material would need to be reacted for so long that the foils would turn into powder. You'd be left with gallons and gallons of acid along with fine particulate and un-reacted parts. A huge mess for sure. Cap removal is unfortunately a must.

ETA: An iodine leach will not work.

 

[FrugalRefiner]

I agree with goldenchild, if you can't spend the time to separate the tops, watchbands are not a good material.

canedane, I'm not so sure an iodine leach would work in this case. It's effective on plated gold, but watchband tops are gold filled. It might not penetrate the depth of the alloyed gold. I don't know. Just thinking out loud.

Dave

 

[galenrog]

I am considering setting up a separate workstation for iodine leaching. Part of that is much study about the process. That study tells me that it is very effective for gold plating. Gold filled on stainless appears to be an exercise in frustration, when using iodine, at least until I gain much more experience.

When I encounter precious metal scrap that I am either not equipped for, or uncomfortable with, I set it aside until I find a buyer.

Time for more coffee.

 

[Lady_Leprechaun]

Thanks so much for the info everyone! I'll just keep plugging away until I get all the caps removed. Some of them are stubborn little buggers. I have over 1,000g of these things so it will be a lesson in patience for sure. I'll avoid watch bands in the future. Clearly not my cup of tea. Does GF jewelry typically require so much disabling before processing? I would think not, but heck it's still a lot of base metal to deal with, so IDK.

 

[FrugalRefiner]

In general, gold filled jewelry doesn't require the manual disassembly that watchbands do.

The thing to always keep in mind with gold filled, is that the gold is all on a very thin, outside layer, just like gold plate. The jewelry usually meets the minimum requirements for gold content when it leaves the factory. Once someone buys the piece and starts wearing it, that outer surface of gold starts to wear away. Always assume a lot of wear on gold filled.

And yes, it's a lot of base metal to dissolve, so consider the cost of acids and waste disposal as well.

Dave

 

[nickvc]

You could use reverse AR on these, that means covering the bands in nitric and adding small increments of HCl to dissolve the gold and copper, do not add too much HCl as it will attack the stainless, once all the caps are dissolved filter the solution and then de Noxx using sulphamic before precipitating the gold.
This needs doing in a fume hood or outside with a fan to blow the fumes away from you also away from any metal structures or cars.

 

[snoman701]

You could use reverse AR on these, that means covering the bands in nitric and adding small increments of HCl to dissolve the gold and copper, do not add too much HCl as it will attack the stainless, once all the caps are dissolved filter the solution and then de Noxx using sulphamic before precipitating the gold.
This needs doing in a fume hood or outside with a fan to blow the fumes away from you also away from any metal structures or cars.

Good idea in theory, but it doesn’t work as clean with watch bands. I’ve used it more than a few times on stainless aerospace parts...but when I tried on watch bands they failed to maintain passivation.

If it’s going to work, and that’s a big if, you first have to dissolve all the base metals with nitric/sulfuric. Then decant/filter and add fresh nitric.

Plus, the stainless used is pretty cheap. I wouldn’t be surprised if it doesn’t have enough Cr to maintain passivation.


Sent from my iPhone using Tapatalk

 

[goldenchild]

Thanks so much for the info everyone! I'll just keep plugging away until I get all the caps removed. Some of them are stubborn little buggers. I have over 1,000g of these things so it will be a lesson in patience for sure. I'll avoid watch bands in the future. Clearly not my cup of tea. Does GF jewelry typically require so much disabling before processing? I would think not, but heck it's still a lot of base metal to deal with, so IDK.

Please let us know if your final weight of caps is around 300 grams. It's a good data point.

 

[Shark]

I use a pair of flush cutters, these are cutting pliers designed to leave no sharp point on the material to be used. Get the cheap ones at Wal Mart or Harbor freight. They won't last long if your doing a lot of bands. I wrap a band around my index finger, and catch one cap between the pliers from the narrow side and pinch. This will cause the cap to raise up some in the center. Now catch the cap long wise and twist it from the long end and the cap will roll right off most of the time. New cutters will be to sharp and may cut the cap, but once used a few times the edge dulls and you can get up some speed. It's still slow, but a lot faster than dissolving everything in acid, and produces much less waste.