Gold Plated Pins

[snoman701]

Here...the braggart is at it again.

I spent a couple hours shoveling hydroxide waste today, so that means I got some free XRF data on some of my scrap.

1 lb of what I would call a medium sheen, thin, bent sheet construction molex style pin came in at 1.25% Au by weight. Crucible was brand new for this melt.

1 lb of half coated ENIG pins that I would normally not waste my time picking up came in at 0.2% Au by weight. These were dirty and had on average a 1/4" of copper wire sticking out the back. Frankly, some of that gold likely came from the crucible from the first batch of pins that were melted.

Analysis made by desktop thermo fisher energy dispersive XRF. Samples were pin samples from the above lots which were melted via induction heater. Pins were cut, rolled out & cleaned lightly with hand soap and pumice. Analysis performed by an operator that Lou considers an expert in the field and there was an offer to purchase based upon assay.

Just some good data. I'll see if I can find some pictures to post later.

 

[niks neims]

1 lb of half coated ENIG pins that I would normally not waste my time picking up came in at 0.2% Au by weight. These were dirty and had on average a 1/4" of copper wire sticking out the back.

wow, that is a lot!
i was under impression that eaven full coated pins from newer motherboards (>p4) are yielding no more than 1g/kg...

too bad

some of that gold likely came from the crucible from the first batch

cool info, thanks man

 

[anachronism]

Put some pics up but how do you know they were ENIG plating thickness?

 

[snoman701]

Put some pics up but how do you know they were ENIG plating thickness?

They just have a really transparent look, are overly reflective, and I can wipe through the gold layer with the rubber on my phone case. So I guess it may not be ENIG, but it's NOT quality plating.

These are pins from airbag wiring harnesses. According to Yazaki, the only place gold plated conductors are used in automotove harnesses are airbag related.

Pic attached.

 

[niks neims]

mind sharing the pictures of the first kind of pins, also?

 

[snoman701]

Ok, so I lied. Actually, my memory just sucks right now. The gold was 1.4%

You can figure out which XRF results are which, and you can see that I clearly didn't remember how much I had either. Just shy of a pound and only about a half pound of the junky pins. I had enough to get a good melt, and a good sample.

But the attached pic shows similar pins as well.

 

[goldsilverpro]

At 1.41% (1.47 - .06) gold, that's $266/pound. No offense, but I don't believe it.

 

[snoman701]

At 1.41% (1.47 - .05) gold, that's $266/pound. No offense, but I don't believe it.

NONE TAKEN!

I was shocked.

Even the guy that melted them said that if it wasn't a fresh crucible, he would have attributed it to picking up gold from a previous melt.

 

[goldsilverpro]

With a good sample, fire assay never leaves a doubt. With XRF, there is always a doubt for something like this, in my opinion.

 

[snoman701]

I don't doubt whether the reading is correct. It is. There is no doubt in my mind that the pin sample contains 1.4% Au.

The doubt would be whether the pin sample was a representative sample.

That doubt would still exist if it were a fire assay.

Or are you just talking about taking a few pins and trying to oxidize off some of the copper in the fusion? (Is fusion the right word?)



Sent from my iPhone using Tapatalk

 

[goldsilverpro]

You now know the Au content on the surface of the pin sample.

 

[Lou]

I believe that the analyst he uses preference is to roll out the pintube sample as taken from the induction furnace and polish the surface before using XRF. If the pin tube was not polished after rolling to size for the aperture coverage, then gold transfer from the rolls is possible. Only thing impacting the result would be phase segregation or tungsten, which often shows up as Au on Energy Dispersive spectrophotometers.


Rather than fire assay, a good digestion of the pin tube's resulting product in nitro-sulfuric acid would yield fine gold.

 

[snoman701]

The rolled pin tube was polished, and there was good aperture coverage. I don't know where tungsten would come from unless there was contamination on the new crucible from Morgan.


Sent from my iPhone using Tapatalk

 

[snoman701]

I stopped to visit today and discuss the controversy.

From his experience:

If he has just melted karat scrap, pulled a pin and rolled it out...then immediately melted fine silver, and pulled a pin and rolled it out, without cleaning the rolls and without polishing the silver, he will often see a 1/4 of a percent of gold via contamination from the rollers, but rarely is it more than that.

He again reiterated that he would have attributed some of the gold to contamination from the crucible, if it wasn't a brand new crucible.

He did say that he sees a good amount of this type of scrap, and that these are quite high in comparison to what he normally sees from melting pins. I pointed out my observation that he did offer to buy based upon the assay, and his response was quite emphatic that it would be in his best interest to have the number come in lower!

I will say that his initial subjective appraisal of the spectral analysis, without referring to the actual counts, just the spectrum as it shows up on the screen...was that it would not come in anywhere near 1.4%.

With all of that, he is quite insistent that I return the ingot to him. We will grind the surface of the ingot to hopefully avoid any surface stratification, and run an xrf off the bar itself. I imagine that if he is still annoyed, he'll end any controversy by remelting, pulling another pin, then running it through the wavelength dispersive XRF.

I don't have time to digest the pin in acid, or I would.

 

[niks neims]

ok, so the one kind of pins came from automobile air-bag harnesses, any idea where did the other kind of pins came from?

 

[snoman701]

Only thing impacting the result would be phase segregation or tungsten, which often shows up as Au on Energy Dispersive spectrophotometers.

I think that is because the tungsten L beta 1 excitation energy is 9.672 KeV, which is very close to the gold L alpha 1 spectral line of 9.713 KeV. (please correct me if wrong)
On further Edit: The niobium identified in both samples shown above is possibly/likely erroneous as well? In this case their spectral lines occur at 2.166 KeV for the Niobium L alpha and 2.120 KeV for the Gold M alpha.

But what would cause excitation of gold, without any excitation of tungsten at the K spectral lines? I feel like if it were tungsten, there would still be some trace of tungsten represented within the sample.

On Edit: Nevermind, Maximum KeV is 50, the K spectral lines occur at 59 & 68 KeV for W and Au, respectively. Even with, shouldn't you see both L alpha and L beta lines for any present sample at minor and trace concentrations?

ok, so the one kind of pins came from automobile air-bag harnesses, any idea where did the other kind of pins came from?

Not a clue...sorry.

 

[snoman701]

Pins were analyzed again today by grinding a good depth in to the bar.

Analysis showed 1.49% Au

I think that is because the tungsten L beta 1 excitation energy is 9.672 KeV, which is very close to the gold L alpha 1 spectral line of 9.713 KeV. (please correct me if wrong)

This is correct. Especially in hand held units, tungsten and gold can be misidentified as well as iridium/platinum/gold.

On further Edit: The niobium identified in both samples shown above is possibly/likely erroneous as well? In this case their spectral lines occur at 2.166 KeV for the Niobium L alpha and 2.120 KeV for the Gold M alpha.

This is incorrect. The niobium is likely a second order interference that occurs at Niobium's K line..

 

[anachronism]

At 1.41% (1.47 - .05) gold, that's $266/pound. No offense, but I don't believe it.

I've been wrong before and I'll be wrong again I'm sure, however I'm with Chris on this. I've processed some pretty mean pins in my time the best being from some Russian telecoms (with Nickvc) where the gold was coming off in sheets. These were still not 14g per Kg. These pins do not look anything like the hue I would expect from high depth plating in fact it looks like the cheaper end of the scale.

As I said before I could be wrong however my head is telling me that your result isn't practically correct.

 

[snoman701]

At this point, I honestly don't care if there's 0.1 g or 4 grams in the bar, I don't have a steady supply of them, I don't know the source...so it's sort of a fools errand to continue to debate it.

The only reason I wanted to perform the analysis in the first place was to see a range of values from what I felt were good quality to what I felt were pretty low quality.

The only reason I shared is because I thought people would appreciate seeing an assay performed by an expert analyst. Not the case I guess.

 

[FrugalRefiner]

Snoman, thanks for sharing your experience. I thought the details of how the samples were prepared were particularly interesting. I will probably never process the exact same material you did, so the yield numbers aren't as significant to me as the process, but I'm only speaking for myself.

Dave