Removing gold plating from pin

Hi I have recently come into 4 pounds of what tests with an x-ray as 49%gold 39% copper and 11% nickle just hoping someone would be able to give me some tips on the best way to remove the gold from them. I've been reading a lot about different methods and I'm not sure which one might work the best for what I have. Thank you in advance for any advice or tips you can help me out with.

Welcome to the forum.
Unless you melted the pins the xrf reading will only tell you the surface reading so do not assume you have loads of gold just sitting there.
Take a test sample say 10 or 20 pins and add a small amount of Hcl enough to cover and add a drop no more of hydrogen peroxide, this is the AP method commonly used on the forum, it may not be really fast but works, do this outside away from kids and animals and leave until the gold foils float free, this should give you a better indication of what to expect if you do decide to try and refine the pins yourself, most pins run around 2 grams of gold a pound but there are exceptions.

From what I understand that 11% nickel might give you some problems in refining.

It isn't 11% nickel. It's only what the XRF sees of the surface. X-rays can only penetrate a small distance from the surface so it sees the gold on top the strongest, the thicker nickel layer is shielded partly by the gold so even if there is more nickel than gold (usually by a factor of 5-10) it reports less of that. And lastly the copper base metal is shielded by both the nickel and gold.

False readings because the person working the instrument doesn't know how it works.

With experience you could build up a knowledge that a certain percent gold correlates to a certain plating thickness, but then you have to take the area / mass factor into your calculation to get a ballpark figure of how much gold your sample contains.

Göran

Thank you all. I was figuring the reading was too good to be true! I just had my buddy who works at a scrap yard hit them with the xray. When I do a sample like that should I break them in half they seem pretty solidly covered. From what I read it seems like the inside metal may need to be exposed for it to get in there and separate. I will try this soon. I figure I got it I might as well figure it out. Its a pretty interesting process I'd just like to know as much as I can before trying so I can keep safe and not ruin them all somehow.

Just sell them on eBay.

If you want a correct reading with an XRF, then you need to melt the material, stir it well and file a window into it, you need a homogeneous sample without any surface oxidation or slag to throw the measurements off. Also you need to take melt losses into account, copper will oxidize, zinc evaporate but gold will only concentrate so it will give you a higher percentage than the starting material. Weigh it before and after melting it.

You probably have less than a percent gold and then the error margin of the reading will start to make a huge difference. The XRF I used in England had a 2 sigma error at 0.5% to 0.3% on the measurements I made. With only two exceptions, all of the plated pins I've processed so far have been less than 0.5% gold on average.

Göran

Progress. I think I'm on the right track. Thanks for your help.

That looks like spring loaded test pins. Used in circuit board test equipment.
It's been discussed on the forum before, but I don't know if there are some yield numbers to go. I would expect a steel spring inside the pins.

By the look of it, you used a lot of hydrogen peroxide.

Göran

I honestly have no idea what they are from. Will have to check to see about the spring. I read recipies that said 2/1 hcl/hp is that too much? It seems to be working just very slowly.

First yeild from 2 ounces of pins. Haven't been able to get a weight yet.

I do not understand why you melted it before refining.
I do not think weighing it now will tell you much at this point.

What are we looking at there ? 2 ounces (60 grams) of pins will likely give you around 0.2g of pure Gold.

Could you explain what you did to get that metal blob? And what kind of torch or furnace you used to melt it?

I ask because it looks like it still has loads of copper in it. And it looks like you didn't get it hot enough for long enough. Or else it would have formed a nice, fairly round, button.

Maybe if you give us some details we could help make your next try even more successful.

I used a torch with mapp gas in a crucible with borax. Yeah I'm kinda winging it here. I hadn't noticed til I melted it there was like 3 little pieces of the full pins left in there so it may still have copper :/ I've thrown in another batch and I'm going to let it sit longer and check through the flakes better when I strain it to make sure there are no pieces left. If theres a better way I'd definitely appreciate any tips.

Once you're down to the foils, you should dissolve everything that left in AR, poor man's AR, etc. Treat for excess oxidizer, lead, silver, etc. Filter, then drop with the reducer of your choice. Then you'll have something relatively pure to melt. There's a lot to learn to do this right.

Dave

As Frugal has said, there is more steps if you want a more pure clean gold button. But let me warn you, 4 pounds of those pins will leave you with a huge amount of waste solution if you keep doing the AP process. Are you prepared to process the waste solution to make it safe for you, your neighbors, and the environment? Practice with the waste chemicals from this first try to make sure you know exactly how to make the waste safe again. It will give you a good idea of how long that process can take.

Also, don't rush. It will take AP a good long while to dissolve all of those base metals. If you keep doing small batches it could take months. But if you do larger batches.....it could still take months. lol.

Personally I'd do a sulfuric acid deplating cell for those pins. It would produce allot less waste chemicals. But before you try anything like that please be sure you know how to handle these chemicals safely. All of them could hurt you, but concentrated sulfuric acid (especially when hot) is super dangerous. One tiny little splash in your eyes and you're likely to never see anything again.

I'm quite glad that you chose to do a small trial. Instead of doing like a lot of people do and just throw chemicals on everything then panic when everything goes wrong. Good job. Keep reading, keep learning, and you will have a great little button of gold to be very proud of.

Thanks for all the pointers. I don't have proper ventilation for the more caustic chemicals. I have to do it in an enclosed garage. Also I hadn't really thought yet about how to bring the waste solution back to safe. I'll need to look into that.