Stainless steel on pins question

I have 11 pounds of military connector pins that have a passivate stainless steel sleeve on each pin. They have been in HCL soak for over a week with no change to the stainless except for a little black coloration to the solution and the stainless has a slight black coloration to it. I have found an older thread on here and will post a link if any follow up to that by the OP or any others have rid the pins of the stainless. Any advice will be appreciated.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=34&t=9633&p=93370&hilit=military+pins#p93370

I have seen high grade pins with a stainless steel locking band around them, I have always removed this band, before treating the pins for base metal removal, I have not seen gold plated pins that had a stainless shell, I have seen pins that are flash plated or partially plated also, so I am not real sure what type of pins you have.

Iron can give problems, so if it can be removed it should be, stainless steel contains iron, it will dissolve in the hydrochloric acid solutions, although very slowly, and until all of the base metals (including the iron or stainless steel), any dissolved gold would plate back onto the base metals (this could be what the black coating you see on your material), iron will also push copper out of solution, although both can remain in the chloride leach together, if enough iron is involved the leach can change from being a copper II chloride leach to a ferric chloride leach, this can be dealt with if you understand the two different leach's. Ferric chloride looks alot like the copper II chloride leach but the two will act somewhat different, the color changes during porcesses act differently (more noticable if heating the solutions, copper II chloride can be regenerated easily, ferric chloride is not as easy to reuse, heating Iron chlorides, can also form iron hydroxides, which are insoluble even in acids.

keep iron out of your process if you can, it can be dealt with, but it is always best not to have too.

I wonder if sulfuric acid could be used to eliminate the SS. I gues it would depend on how much there is.

depending on what way you intend to process them would determine what you need to do about them. stripping cell or AP, the stainless steel will not effect these processes.if you dissolve the foils with hcl/Cl, they shouldnt cause very much trouble as long as you filter as soon as they dissolve.

If these are nitric resistant stainless you could dissolve the pins out of the sleeves. And screen out the stainless.

Perhaps worth a test?

Crow King and me have decided to add a bubbler to our HCL soak to speed up the removal of the copper aspects and then to HCL/CL and then strain the sleeves away. Would any of you expect any of the stainless to go into the solution? Has any of the membership tried this and or have any comments? Joe

i have. the stainless steel is not effected much if at all by the AP process. it will be mixed with the foils. dissolve the foils and filter as soon as the foils dissolve.

Thank you Geo, will keep this thread updated with our results. Joe

If all you want to do is dissolve the stainless steel, heat your hydrochloric acid, it speeds the reaction up rapidly. It may not be necessary to totally dissolve it as it may loosen the bands enough to be able to remove them easily by hand so test one periodically to see how it's progressing.

I have had success refining stainless steel watch bands with gold inlays by digesting the gold in a flip flop type of aqua regia.

For obvious reason, and some not so obvious, this reaction should be done in a good fume hood!

By making up an acid mixture of 50% nitric acid and 10% hydrochloric and the rest water, the stainless steel passivates and is not digested by the reaction, some of it dissolves but very little. The karat inlays dissolve completely. The gold in solution is then filtered and the substantial excess nitric is eliminated with sulfamic acid. The gold is dropped normally after the nitric is eliminated.

Use as little acid mix as possible to just cover the pins and shake the pins to keep the acid changing between the pins. The watchbands were high in percentage stainless with small percentages of gold and this process effectively digested the karat gold. The shielding afforded by the stainless sleeves on the pins may cause this to react more slowly to start, the watchbands obviously had the gold exposed.

Start with a small quantity in a beaker to check it out.

Good luck!

As 4Metals alluded, this process works, but be very cautious in the amount of HCl used. If you go overboard with the muriactic you will have a run away NOx genrator on your hands. You will also most likely have loses due to the gold solution boiling over and spraying a fine mist of the solution out of the reaction vessel.

On the subject of sulfamic, you'll also need to err on the side of caution as the reaction is very 'foamy' and tends to triple or even quadruple in size when the sulfamic is added. You are going to need lots of patience when precipitating the gold as the high nitric solution will feed on any precipitated gold until it is all used up. This coupled with the exothermic (self-heating) nature of the reaction makes for a very laborous precipitating process.

Steve

After the copper is gone, there is stainless and gold left. I would agree with 4metals that the high nitric low HCl will work well on this combination. I would, however, reduce the HCl to about 3%, to start. The formula would be 50% HNO3/3% HCL/47% tap water, all percentages by volume. Run at room temperature. I would put the SS/Au in a bucket and cover with a little excess of this solution. I would expect that foils would dissolve within an hour or two. It will help to occasionally rotate the bucket gently back and forth to force solution exchange inside the SS sleeves. The same solution can often be used to process several batches of material. If it slows down too much, add another 2 or 3% HCl.

I have run many 1000s of pounds of similar material using this solution. After filtering the garbage out of the solution, I always precipitated the gold directly from the solution with hydrazine sulfate (HS). It probably took a HS/gold ratio of from 1:1 to 3:1. No dilution or elimination of nitric is necessary. I just sprinkled the HS on the solution, in increments, and stirred it in (there could be foam so make sure the precipitating vessel has enough space). Brown gold powder will appear fairly quickly. Moderately dilute Hydrazine Hydrate could surely be used instead of the HS. Test effluent with stannous chloride.

I always re-refined the gold powder in AR.

As with anything new, run very small test lots first to make sure it works and to allow yourself to get the "hang" of the process. Although I don't think you'll have any problem with stainless steel, some weird alloys will, as Steve said, dissolve in the solution and produce a runaway reaction. Also, some obscure alloys introduce something that inhibits the hydrazine from dropping the gold. Try a little sample first.

I remember the day when people would have paid a fortune for information like this! If they could find it.

This forum is one amazing place.

Chris,

It's interesting that you stated hydrazine does not require the elimination of the free nitric as I have never had luck with using hydrazine directly on these solutions except when the nitric has been removed first. I'll have to give it a shot again on one of my buckets today and see if it works without removing the nitric.

4Metals,
You won't have to wait very long to see this information all over the web and for sale on ebay now that the cat is 'out of the bag'. It's amazing how quickly some secrets become the next big 'web sensation' isn't it?

I predict we'll start seeing a lot of youtube videos and questions on the subject now. The one thing that may keep a lot of guys away from this process is the high cost of nitric acid... and the brown fumes for those faint of heart.

Steve

It works and works well but it's not a process for a beginner in my opinion it's has many variables as has been pointed out and it takes experience and patience to achieve a full recovery, for most I'd still advise removing the stainless with hot hydrochloric before attempting recovery of the gold.
I can see this process becoming a nightmare for the forum if tried by complete beginners :shock:

I've run a lot of pins with SS sleeves. If I wanted some gold from these immediately, I used cyanide to strip just the visible gold. The pins, which still had gold under the sleeve, were then melted with other copper based gold scrap and shipped, in bars, to a primary copper smelter.

Steve,

Success with hydrazine seems to be dependent on the base metal alloy or, maybe, some coating on it that dissolves. I never had any problem with SS.

Its been nearly 7 months and those pins have been in AP. A bubbler ran for 4 months. One bucket inside the other with the drilled holes, the top bucket holding the pins. After a month we noticed the AP was attacking the stainless along with the copper. Now it appears we have a Ferric Chloride instead of a Copper Chloride. It is red solution in color with red mud mixed in with the gold foils and undissolved pins. We took the top bucket and placed them into a new bucket and began washing with water, the mud will turn the water red and after a dozen washings it looks to need a hundred more. We have not started working with the bottom bucket but in 2 gallon of solution there is 2" deep of mud material which looks to be gold foils in gray mud, similar to Copper I, and more red mud. How can the red iron mud (stainless steel) be dealt with to save the gold? I have read of dilute sulfuric acid being used? Would the Copper Leach, having turned to a Ferric Leach, be responsible for some remaining undissolved copper from the pins to be left over?

A small amount of HCL in your rinse water can keep the red rust from forming. Keep it acidic.

Is it correct that I am to assume that my now Iron Leach is in the form being the same as Copper 1 or as it is, Iron 1? If so adding more HCL will turn it to Iron 2 and I will have my gold foils and pushed out copper to deal with? Would I then take my strained gold foils and pushed out copper and separate these 2 with heated HCL washes? /any and all help is appreciated as I am dumbfounded with the mess I have made out of all this potential value, lots of glitter in that red mud..... :|

JH123

It can be a mixture of copper chloride and chloride solution, the mud can contain copper I chloride, and iron Hydroxides (red mud).

Decant solution from powders, give powders a wash it hot water, if there are pieces of undissolved pins screen powders through a screen in the bottom (I buy plastic cups with a handle with nylon type screens (not really sure what type of plastic the screen is but it hold up well to the acids), these are for use in the kitchen, I use this screen a fiberglass stir rod and a funnel and a jar to separate the powders from larger pieces of undissolved metals, the stir rod can also help to break the crystals up to go through the screen, this make acid washes later more effective, sometimes water or acids ETC. are used to wet the powder to help the go through the screen easier or I may add a little acid and peroxide while getting the material screened kind of making it easier to screen and somewhat pre-treating the powders at the same time. I save the small un-dissolved metals the either go to my burn pile for filters or my stock pot just in case.

The gold will also be foils in this mud; you may find some of the larger gold foils can be separated in the screening process.

The copper I chloride will be soluble in warm HCl, I would wash these powders in heated HCl washes till the solution clears, stir powders in these hot washes and then let them settle, before decanting solutions, then use hot water washes, till the water wash is clear, the red powder and gold will not dissolve in this HCl solution.

Iron hydroxide (the red powders) are very hard to dissolve into acids, the gold will dissolve a lot easier that the red powder, you can dissolve the gold foils in HCl/NaClO (bleach) leaving most of the red powders (rouge red iron powders) undissolved, some iron can also go into solution and can also give a yellow color looking like dissolved gold, or could color solution a green, but it is difficult to oxidize the iron hydroxide and you should be able to recover your gold from this solution after heating solution to remove free chlorine from solution, after letting solution sit till clear filter solution into a clean vessel and use SMB or ferrous sulfate(precipitant of choice) to precipitate your gold, use your stannous chloride to determine when all of the gold has been precipitated out of solution, the remaining solution may still be colored yellow or green with some dissolved iron.

Wash the gold powders per Harold’s instructions.

You will need to refine the recovered gold again the second time (but it is easy the second time).