Gold on Nickle stainless steel alloy

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yvonbug

Well-known member
Joined
Oct 20, 2007
Messages
174
Location
Mtn. Ranch, CA. USA
Ok, I've started a new thread, because I've a different metal to deal with. If I try to slowly dissolve the gold off the nickle/stainless steel body, and some of the metal other than the gold goes into solution with the gold, could I drop it out before I drop the gold? And if so, what would I use? If this is a bad situation,would it be better to try the electroplating method? And what would I use for that? Never have done that before, (but it sounds interesting, and I want to try it.) I think this could be fun. Here's a picture of the part.DSCN0689.JPG And Thanks again to Geo for identifying the metal!
 
Actually, AP is very poor at dissolving nickel. That's why foils recovered through the AP process is so very contaminated. I'm sure it dissolves some of the nickel but certainly not all of it.
 
Or if I dropped the gold out, using sodium sulfite, would that leave the other metals behind in solution? It'd probably be contaminated gold, but then I could refine it again?
 
Palladium asked an excellent question. In the previous thread, Rather thick gold plating on aluminum, Geo mentioned using "concentrated nitric acid and adding HCl by the drop at a time". I believe GSP introduced this method to the forum, and it has come to be known as "reverse AR". Is that what you're going to try, or something else?

Dave
 
I'm kind of lost here.
Thought you would try implies you haven't done it that way yet. What type of solution are we talking about?
 
If you're going to try reverse AR Then I'd recommend some in depth research first.

It's very prone to a runaway reaction if you get your HCl amount too high. That's a reaction that gives off so much heat that it becomes self sustaining and increases as the temperature gets higher. If it gets away from you it can get messy and dangerous very fast.

Also you need to work out how to get the gold from the gold chloride in a solution which effectively has an enormous amount of excess Nitric.

I haven't had the need to do this very much at all. My experiments with it have been very small scale.
 
When dealing with massive pieces of base metal with a tiny amount of gold on the surface it really doesn't pay off to dissolve the base metal. It is costly and creates a lot of waste.

In this case the sulfuric cell or cyanide leaching is the only reasonable way to go. Then you can sell the metal as scrap when the gold is gone.
Sulfuric acid is dangerous, but cyanide is lethal, so for me the choice was simple.

First time I tested the sulfuric acid cell it was like magic, ran a couple of kilos of anything from heavy connector shells to gold plated stainless spoons. The thing that limited how long I ran the cell was the amount of water absorbed, but that was totally my fault and it was a small test setup just to get the feeling.

Göran
 
I did mention that I'd like to try the reverse electroplating method also. Learning new stuff is fun to me. I watched a youtube video on this, but the guy used real strong sulfuric acid. I've got some battery acid that I just bought, so it's fresh. Anyways, the process looked real easy, and I thought it would be better than anything else. Like less unfortunate mistakes to be made. But I was also considering the (reverse ar) method. But now I'm leaning towards the electroplating method, cuz it sounds a little safer. (is that a word? Safer?) I've got a battery charger, a casserole dish, lead to make the cathode? with, and I can get some copper mesh from the craft store to make a basket-anode. uh, what do you think?
 
Your fresh battery acid will dissolve a lot of base metals, including your copper mesh anode basket. Concentrated sulfuric acid is needed. Diluted acid, like your battery acid, is very different. You need to study in depth, not just watch a youtube video. I don't mean to be harsh, but the sulfuric stripping cell has been discussed in depth. Study before you try it.

Dave
 
Yeah, just as Dave stated, you need concentrated (>90%) sulfuric acid. As it will absorb moisture over time it is always best to start with 96%.

The theory (as I understand it) behind the reverse cell is that concentrated sulfuric acid actually oxidizes the surface so it is covered by a protective layer. That way the only thing that is affected is the noble metals that are dissolved.
Once the concentration drops below a certain point the additional water makes it possible to dissolve the metal instead and it is a quite distinct point where the cell starts to work bad.
When the acid can go after the base metals it will do it and the precious metals will be mostly untouched.

Göran
 
Owltech said:
Iodine/Iodide works great on this type of scrap

I agree with the approach in terms of leaching. People do need to find a surface leach process rather than dissolving loads of base metals on this kind of gear. I don't advocate the sulphuric cell personally. It's vile and remarkably unsafe when used with a jam jar/home material setup.

Frankly the eco goldex stuff appears better overall.
 
I didn't think anyone was being harsh, just trying to drive a point home to me. Yes, I'm reading my Ammens and Hoke. Ammens kinda lost me this time. Going to look up leaching too. I'm getting old enough to want to take short cuts. Which isn't safe or good for my brain. Wanted you guys to tell me everything I had to do, and that's not right either. So, with that said, Everything you all have said already, Thanks for helping!
Leaching sounds interesting, also. So I'm off to study up on these last 2 methods. I'm never too old to learn new stuff!......
 
Well, I've been checking out the reverse electroplating method. While I've been waiting for my order of 93% sulfuric acid to arrive, I tried out a small (just 2 parts) batch using the battery acid I had bought. And found out it does just what Goran said. It worked a little bit but then started coating the item with copper from the basket. But, aside from that, the battery charger I was using kept cutting out, like it was on a trickle charge. I had it set on 2 amps and 6 volts, then 2 amps and 12 volts. Both times it started cutting out and then it finally just quit. On this particular charger the next amp setting was 15 and I didn't want to go there. So, I went and bought me a little charger today that is only 4 amps. with 6/12 volts settings. Anyways, this charger is a High Frequency charger/maintainer. Is this going to ....not work with what I'm trying to do? It's a Viking 4 amp fully automatic microprocessor controlled battery charger/maintainer.
 
When it comes to electrochemistry, a smart battery charger is not a good choice. It finds out that it isn't a battery it tries to charge and treats it as either a fully drained battery or a faulty battery. Old time battery chargers with a big transformer, rectifier... and that's it, is a lot better. It will deliver the power you want until it blows a fuse.

Best thing to use is a lab power unit. With both voltage and maximum amperage settings. Then you can fine-tune the reaction. It works for smaller units, for a larger setup there are specially made power supplies for electrolytic baths.

Göran
 
OK, Thank-you. I'm going to return the little charger and ask around for an old one. One of our friends has got to have one sitting around in their garage or back shed. I've got my concentrated sulfuric acid and I don't want to mess with it until I've got everything else set up right. One other thing, does it make any difference if I use a thin sheet of copper with a zillion holes punched in it, or should I use copper mesh? :?
 
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