Gold filled with stainless steel base

[delboy9891]

Hi folks, after reading hokes book and searching the forum I have a gold filled chain that weighs 480 grams, I filed one of the links and it is a Silver colour underneath which due to the weight and being non magnetic I believe to be stainless steel, After some research I believe the best way to get the gold off the base metal is to use reverse aqua regia, after reading some of the posts on here I will be using 4 parts Nitric Acid ( undiluted ) which will passivate the stainless steel to 1 part Hydrochloric Acid , my question is am I on the right track with this method? any advice would be appreciated, picture of chain below

 

[Shark]

Make sure it isn’t silver under the gold.

 

[delboy9891]

Make sure it isn’t silver under the gold.

No, tested it with my Silver test solution, definately not Silver

 

[snoman701]

There is usually silver under the gold as Shark said. Soak it in nitric. Then the gold foil may help loosen up the foil.

If you aren't good with regular AR, don't use reverse. And go slow. Do NOT try to do it with 3:1 HNO3 / HCl. You run the risk of losing passivation.

 

[delboy9891]

We call

There is usually silver under the gold as Shark said. Soak it in nitric. Then the gold foil may help loosen up the foil.

If you aren't good with regular AR, don't use reverse. And go slow. Do NOT try to do it with 3:1 HNO3 / HCl. You run the risk of losing passivation.

We call gold over Silver Vermeil in the UK, I bought this chain as Gold filled, I have tested the link I filed and it is definately not Silver, wish it was, I have used Aqua Regia before with success, pic below but first time trying reverse aqua regia and after consulting hokes book and posts from the forum thought I would give it a try not with the full chain but with a couple of links and see how it goes, maybe 50 ml of Nitric and use a 3ml dropper for the Hydrochloric Acid at a time for incremental dosing

 

[snoman701]

It's not a silver core as vermeil would be, it's a silver plating between the stainless and the gold.

 

[delboy9891]

It's not a silver core as vermeil would be, it's a silver plating between the stainless and the gold.

I didnt know that, so how should I proceed with this? Im a bit confused now, I will try soaking it in Nitric and if it does have silver plating between the gold and the silver maybe the gold foils will drop off, that would be perfect, should I use hot nitric or just add it cold?

 

[snoman701]

I process all gold filled the same. I soak it in nitric until all base metals are dissolved, then I decant/filter and dissolve the remains in aqua regia. It works for most stainless base material unless it's really thick.

 

[delboy9891]

I process all gold filled the same. I soak it in nitric until all base metals are dissolved, then I decant/filter and dissolve the remains in aqua regia. It works for most stainless base material unless it's really thick.

Thanks, do you just soak it in cold undiluted Nitric or dilute nitric heated?

 

[snoman701]

room temp 1 Nitric : 2 water, it'll heat itself, I finish with heat

 

[delboy9891]

Great, thanks for the advice, I will give it a go with a couple of links from the chain and see how it goes

 

[Jado]

Another vote for Nitric. HCl isn’t recyclable after mystery metal and it creates a lot of waste. Second choice would be reverse electroplating. I think the big companies all use HFs but that’s not something to mess around with.

 

[Yggdrasil]

Another vote for Nitric. HCl isn’t recyclable after mystery metal and it creates a lot of waste. Second choice would be reverse electroplating. I think the big companies all use HFs but that’s not something to mess around with.

There is no reason what so ever to use HF on Gold filled.
The big boys do not play around with HF unless it is deemed absolutely neccessary, so I doubt they will do that.

 

[nickvc]

If you do decide to use reverse AR then do so under a hood , put your item in a beaker and cover with nitric and slowly add drops of HCl slowly into your beaker and mix , do not premix your acids, the trick is to be able to dissolve the gold alloy and very little of the base material, you will need to denox your solution or use it to dissolve more material.

 

[delboy9891]

Ok I went down the nitric route, the gold foils came off relatively easy, will filter tomorrow, put the foils in aqua regia, denox with Sulphamic Acid then precipitate with smb, I will post my results once that is done

 

[William656]

Ok I went down the nitric route, the gold foils came off relatively easy, will filter tomorrow, put the foils in aqua regia, denox with Sulphamic Acid then precipitate with smb, I will post my results once that is done

Hey there.. how’d it turn out? Any updates? Thanks. Im curious.