Another Solder Issue

GoldRob

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Folks, I want to appoligized for not knowing how to find the answer to this question. I washed the two old connectors In muriatic acid. The solution turned white. After one day the solution was clear and the attached photos are what was left. I am confused that not all the gold concectors had not turned silver. Which I did not want in the first place.

It looks as though the silver content of the solder cemented back on to the connectors. Do I place back into fresh muriatic acid or would I need Nitric to dissolve this type of solder?

Again sorry if this question, has been discussed. Just needing help on a pile or pins and connectors that have solder on them and I am only using muriartic.
 

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Yggdrasil

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Silver don't dissolve in muriatic.

I can't say what happened here, maybe some Indium solder or other dissolved metals. Why was you washing in muriatic?

Once something similar happened to me, I dissolved the tin on some material and got this idea of reusing the acid to start an AP leach.
Most of the pins turned like yours immediately.
I just added some old AP solution to it and it went ok in the end, even if it took a really long time.
Maybe some of the experts here have a more precise description on what it is?
 

GoldRob

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I was trying to remove the solder. The part come from old computer parts. This was just a sample to see what would happen. So I took a razor blade to scrap the cement to see if the gold was still underneath of this tin/? I have attached some photos of this endeavor. I need to read more on how the crcok pot.
 

GoldRob

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Photos.
 

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GoldRob

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A piece inside the acid.
 

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stella polaris

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On your first picture the pinns is after acid as i understand. If gold plated its a good chance that only the contact areas are plated. On female pins that means inside the hole. Outside is not nessesary nor costeffective. The male pin is the opposite. Gold on outer surface but not with in it. Cut two of them open and look at the other side. That would give a good clue.
 

GoldRob

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Stella, I can't remember what they came off of, I had gold fever at the time. I know it was something old. Here are some more photos. Thank you for different ways to tackle these pins.
 

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GoldRob

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The other pin.
 

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butcher

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Just a guess.
It looks like solder is reacting.
Several very reactive metals (most like in solder), one reactive base metal going into solution displacing Hydrogen gas from solution, affecting the pH of the solution, and another undissolved base metal (which could be part of the solder composition then it goes into solution, cementing out the metal that was previously dissolved in solution (not acidic enough to hold both metals in solution), or something similar.

If you have a lot of base metal you may just need to keep going, adding some fresh acid as needed, or refreshing the solution until you get all the more reactive base metals in solution and you can keep them there.
 

stella polaris

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Butcher, it was not all pins that got the cementing.

Can it be a base metal in the pin that make the cementing (reaction serie)? In that case it makes logic that the male pins do not have cement on outer surface if goldplated.

The female ,with no gold plating on the outer surface, should be cemented on outer surface but not in the hole if gold plated there.
 

butcher

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Two different metals in an electrolyte solution (acid or caustic) will make a battery cell, one metal acting as anode will dissolve and plate to the other metal or cathodic material in solution.
 
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GoldRob

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These two came out of AP solution. I stuck them in with these silver and copper contacts. The solution was saturated so I replaced it.
 

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GoldRob

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After soaking in ap.
 

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