Gold or not?

[aussie_noob]

Got old electrical connector samples that I believe are plated with gold, guessing 2.5um thickness.

Took these samples to multiple gold experts who all told me, without hesitation, and with complete certainty, that these have no gold coating. It's apparently fake gold, no surface coating or anything, 0% gold according to every expert i handed these to, five experts. Took only seconds for them to conclude this, all gave the same reaction. One metal worker, a non-gold person, took one look and said 24 karat.
You guys know this stuff well, what do you think?





I did a test. Had them in pirhanna solution (98% sulfuric and ratio'd hydrogen peroxide), been dissolving for few hours at room temp, no stiring.

They were fairly shiny and uniform gold to start with, some sections around scratches or edges have colour changed to dark, with the dark regions growing over time. ie. growing localised corrosion spots where base metal is exposed.

Gold plated or not?

 

[Martijn]

I would believe the non-gold experienced person and auction it on E-bay.
There is however a chance the expert know their stuff.

It could be brass, cadmium, some kind of anodized metal, ...etc.

Why dump a bunch of connectors in piranha solution?
Why not test one connector in HCl? If that does not dissolve, try one in HNO3.
Are all the connectors different that you threw them all in?
Understand the difference between processing and testing.

Does piranha dissolve gold?
What did you expect to happen?
Are you aware of the explosive properties of piranha and the effect of said solution in your face and on your skin should it explode in your face?

 

[Yggdrasil]

Got old electrical connector samples that I believe are plated with gold, guessing 2.5um thickness.

Took these samples to multiple gold experts who all told me, without hesitation, and with complete certainty, that these have no gold coating. It's apparently fake gold, no surface coating or anything, 0% gold according to every expert i handed these to, five experts. Took only seconds for them to conclude this, all gave the same reaction. One metal worker, a non-gold person, took one look and said 24 karat.
You guys know this stuff well, what do you think?


View attachment 63633
View attachment 63634

I did a test. Had them in pirhanna solution (98% sulfuric and ratio'd hydrogen peroxide), been dissolving for few hours at room temp, no stiring.

They were fairly shiny and uniform gold to start with, some sections around scratches or edges have colour changed to dark, with the dark regions growing over time. ie. growing localised corrosion spots where base metal is exposed.

Gold plated or not?

I can't say from pictures.
What I can say is that you have done it all wrong.
Piranha solution has NO use in refining, it is way too dangerous.
Try AP for a while.

 

[aussie_noob]

Yeah, no hcl or nitric, struggling to get, i'm just an individual, no company or connections. Wanted to test chemical inertness of plating surface compared to substrate. It seems way more inert than whatever is underneath, brass? What kind of plating is gold coloured and chemically inert compared to the brass underneath?

 

[anarxi]

https://goldrefiningforum.com/threads/palladium-jackpot.33183/#post-360355
This method can also be used to check gold plating.
If it is a gold coating, the cotton wool will turn greenish yellow, and the surface of the tested object will not change..
there is no gold, the cotton wool will turn black and the surface will immediately become copper..

 

[aussie_noob]

https://goldrefiningforum.com/threads/palladium-jackpot.33183/#post-360355
This method can also be used to check gold plating.
If it is a gold coating, the cotton wool will turn greenish yellow, and the surface of the tested object will not change..
there is no gold, the cotton wool will turn black and the surface will immediately become copper..

Nice test, am I understanding this right?

Cotton swab electroplating test:

### Materials:
- Low-voltage DC power supply (three to twelve volts)
- suspected gold object (anode)
- Wire with a cotton swab attached (cathode)
- Saltwater solution

### Procedure:
1. ** Add saltwater **.
2. **Connect positive terminal** of power supply to the metal object.
3. **Connect negative terminal** to the wire with the cotton swab.
4. **touch with cotton swab** make contact with test object (anode) and cotton swab tip in solution, keep cotton swabs connected wire out of solution.

### Results:
- **Gold Presence**: Cotton swab turns yellow or gold-colored.
- **No Gold Presence**: Swab remains unchanged or turns a different color (e.g., green/blue if copper).

 

[anarxi]

yes, that's right.
I mainly use this test to determine palladium, but I've tested it on gold a couple of times.
It's most practical to test it on a known gold to see the color, to understand this shade..

 

[aussie_noob]

yes, that's right.
I mainly use this test to determine palladium, but I've tested it on gold a couple of times.
It's most practical to test it on a known gold to see the color, to understand this shade..

Hmmm, tried it. No colour change? The gold stuff is coming off, i just can't see anything on the cotton? Too small a quantity or negative for gold? Not sure?
I keep going and the copper substrate underneath the coating starts coming off onto the swab Turning it green. Both coating and substrate come off real quick, tens of seconds to minutes to see changes in metal surface.

 

[anarxi]

you need to touch the cotton swab for 1-3 seconds...
If nothing has come off the material during this time, this is a good sign.
The gilding is present...

In a couple of days, I'll return to my workshop, do a test on my gilding, and post a photo

 

[Alondro]

Yeah, no hcl or nitric, struggling to get, i'm just an individual, no company or connections. Wanted to test chemical inertness of plating surface compared to substrate. It seems way more inert than whatever is underneath, brass? What kind of plating is gold coloured and chemically inert compared to the brass underneath?

So you can buy sulfuric acid... but not hydrochloric... that is nuts. Sulfuric is WAYYY more dangerous than HCl!! For crying out loud, your stomach produces HCl!

In the US, I can buy 4 gallons of HCl no questions asked, as it's frequently used for cleaning pools!

 

[Yggdrasil]

So you can buy sulfuric acid... but not hydrochloric... that is nuts. Sulfuric is WAYYY more dangerous than HCl!! For crying out loud, your stomach produces HCl!

In the US, I can buy 4 gallons of HCl no questions asked, as it's frequently used for cleaning pools!

Many places ut is not that it is forbidden or illegal per se.
But the normal sources do not sell it or even stock it.
Or maybe it has unusual local names.

 

[Yggdrasil]

Hmmm, tried it. No colour change? The gold stuff is coming off, i just can't see anything on the cotton? Too small a quantity or negative for gold? Not sure?
I keep going and the copper substrate underneath the coating starts coming off onto the swab Turning it green. Both coating and substrate come off real quick, tens of seconds to minutes to see changes in metal surface.

Can you get Muriatic acid?

 

[Slochteren]

Why not setup a small sulfiric de plating cell if you have 98% sulfuric.

 

[aussie_noob]

Now got nitric so can just tell, will test soon. However wanting to learn. How to test for gold?
Got pure lead cathode and power supply for reverse electroplating cell. Gold should precipitate into solution at lead due to passivating layer and 98% sulfuric. What do you expect to see for a positive / negative result to a gold layer? Suspected substrate is brass.

 

[Yggdrasil]

Now got nitric so can just tell, will test soon. However wanting to learn. How to test for gold?
Got pure lead cathode and power supply for reverse electroplating cell. Gold should precipitate into solution at lead due to passivating layer and 98% sulfuric. What do you expect to see for a positive / negative result to a gold layer? Suspected substrate is brass.

The applied Voktage will create a thin layer of PerSulfuric acid which will dissolve the Gold.
The moment it comes outside this thin Zone it changes back to Sulfuric acid and can no longer hold the Gold which precipolitates as a black powder.

 

[aussie_noob]

The applied Voktage will create a thin layer of PerSulfuric acid which will dissolve the Gold.
The moment it comes outside this thin Zone it changes back to Sulfuric acid and can no longer hold the Gold which precipolitates as a black powder.

That was interesting to learn! Had no idea about the persulfuric layer and location of precipitation. Makes sense, gold is difficult to dissolve and sulfuric is conductive, so you can get precipitation close to the anode.

 

[aussie_noob]

Dumb question, for the reverse electroplating in sulfuric, I'd guess there's really fine gold particles formed that could pass through filter paper.... how do you catch that stuff? Maybe just evaporate the solution and use another method on the leftover solids? Maybe this is only a small percentage?

 

[Shark]

Filter it out. But paper and sulfuric don’t play well together so you need something that will. I use a small piece of fiberglass insulation and pack it into a regular funnel mouth, just enough to stay put. Stronger version of a Charman filter. The fiberglass can withstand AR, and can be filtered out during normal AR filtering steps.

 

[aussie_noob]

GOLD! Confirmed by nitric. These flakes are beautiful. Just need to remove the lead/tin solder from each piece to improve the yield and karrat. Can't believe that many gold experts were actually wrong. Credit to the brass polisher though, he knew.

Appreciate the help guys, this is ganna be a profitable few days...

 

[aussie_noob]

Might need a hand figuring out how to pre-remove the lead. Solder was used to attach coaxial cables, I assume some kind of heating is best? You guys will know good methods.
Was thinking that heating lead to melting point could cause lead diffusion into the thin gold film causing contamination to the gold flakes. I dunno might not matter? Maybe I'll just aqua regia or electroplate to purify the gold?