Little confusing - AP Process

[Yaz]

Hello everyone!
I started 2 batches of pins few days ago, one batch of 90g fully plated non-magnetic pins and another 400g partially plated pins, those are mixed, mostly non-magnetic and some semi-magnetic ones. All are solder free.
Added 200ml 32% HCl and ~7.5ml 20% H2O2 to the fully plated.
1200ml 32% HCl and ~30ml 20% H2O2 to the partially plated mixed pins.

Solution became pale yellow in both cases instead of pale green. Checked again about 4-6 hours later and solution was colorless.

Both stayed like that til next day, so I added little bit of H2O2 to both and they gave some very pale green and back to yellow about an hour or 2 later.

Couple of more days (about 5 days since the begining) I added 50ml of H2O2 to both and they both turned to a light green color. But again 1-2 hours later it started fading though it kept pale greenish for longer..

Now (few more days later) they are very pale yellow with barely any green tint, then completely colorless after I took those pics

Adding more H2O2 seems futile considering that I'm air bubbling too (unless maybe if I add 1 liter?) Or maybe pour off the solution and let the pins sit in the air for a day?
I'm assuming that or something is cementing out the copper? But colorless like that? Fully plated pins in the jar are non-magnetic and as I mentioned all solder free so basically all/mostly copper I assume.. Both jar and bucket are showing almost exact same behavior. It has been about 8-9 days total now and the reaction is as you see, going backwards .
Should I just wait it out or something need to be done?

Any Idea or help would be appreciated.

 

[Lino1406]

With 20% H2O2 gold may dissolve, check the yellow liquid with stannous chloride

 

[Yaz]

With 20% H2O2 gold may dissolve, check the yellow liquid with stannous chloride

7.5 ml 20% is the same as 50ml 3%. So basically it was 4:1 HCleroxide.

Heck, nothing seems remotely dissolving and gold in solution is definitely not colorless... Either way it would've cemented back out and reaction shoulda carried on.

 

[jmdlcar]

The Peroxide you only needed to add a cap full or very little Peroxide.

 

[g_axelsson]

This is why I don't like people calling it the AP process, as in acid peroxide. What is usually meant is copper chloride etching, and if you have magnetic pins then there is no copper that keep the process running.

In the case of magnetic pins or pins with some solder, any copper chloride that is formed is cementing on the iron or tin so the process slows down quite dramatically. In this case the peroxide doesn't add anything. Use plain HCl and add some heat. It will still be slow until all iron, nickel, zinc, lead and tin is dissolved. After that the copper chloride etch should start working.

If the pins are fully plated then the acid could have a hard time to get through the plating.

Pins are very rarely pure copper, there are a number of different alloys used. Various alloys of brass and bronze is used depending on the application. Common metals used is copper, zinc, silicon, phosphorus, lead, tin, aluminium... and probably a lot more I don't know about. Nickel is almost always used as a plated layer between the base metals and the gold plate.

I've run pins in copper chloride several times and I always started with a healthy dose of copper chloride. Several times I had to add more copper chloride as the copper cemented out and the solution became colorless. After more additions of copper chloride it always started to work.

My advice is to just be patient. Copper chloride will be formed even without any peroxide. Heat will also speed things up. It doesn't have to boil, just keeping it warm will speed up any reactions.

Lead, tin, zinc and aluminium chloride is colorless.

Göran

 

[Yaz]

This is why I don't like people calling it the AP process, as in acid peroxide. What is usually meant is copper chloride etching, and if you have magnetic pins then there is no copper that keep the process running.

In the case of magnetic pins or pins with some solder, any copper chloride that is formed is cementing on the iron or tin so the process slows down quite dramatically. In this case the peroxide doesn't add anything. Use plain HCl and add some heat. It will still be slow until all iron, nickel, zinc, lead and tin is dissolved. After that the copper chloride etch should start working.

If the pins are fully plated then the acid could have a hard time to get through the plating.

Pins are very rarely pure copper, there are a number of different alloys used. Various alloys of brass and bronze is used depending on the application. Common metals used is copper, zinc, silicon, phosphorus, lead, tin, aluminium... and probably a lot more I don't know about. Nickel is almost always used as a plated layer between the base metals and the gold plate.

I've run pins in copper chloride several times and I always started with a healthy dose of copper chloride. Several times I had to add more copper chloride as the copper cemented out and the solution became colorless. After more additions of copper chloride it always started to work.

My advice is to just be patient. Copper chloride will be formed even without any peroxide. Heat will also speed things up. It doesn't have to boil, just keeping it warm will speed up any reactions.

Lead, tin, zinc and aluminium chloride is colorless.

Göran

I only called it AP because that's what I see people mostly use, and I don't have any copper chloride to start with. I do understand it's a CuCl/CuCl2 etching process.

The magnetic pins are only in the mixed pins batch and very little (about ~2 cpu sockets in that mix of 400g), and pretty sure there was 0 solder as I trimmed the pins off the board without desoldering and only the top half. Not saying they wont contain any tin.

Several times I had to add more copper chloride as the copper cemented out and the solution became colorless. After more additions of copper chloride it always started to work.

Thank you, that was helpful!

My advice is to just be patient. Copper chloride will be formed even without any peroxide.

I thought so, but I thought adding some wouldn't hurt seeing how the reaction was going backwards and what I added already probably ended up as H2O by now. It wasn't because of impatience ( I think :? )

Lead, tin, zinc and aluminium chloride is colorless.

I ran across multiple posts through my searches and reading on here seeing people saying that those turn HCl to yellow when in solution. But then again I saw a post saying that CuCl is colorless in solution..
Time for more studying for me I guess.

I guess I'll just leave them and be patient as you suggested. It was just because I searched a lot and didn't find much about the "colorless" issue and I really wanted to understand what was going on and maybe help others facing the same issue .
(An example of one of the threads I found when I searched before posting https://goldrefiningforum.com/phpBB3/viewtopic.php?t=11057)

Thanks alot for the very informative post Goran!


Ps: The goldrefiningwiki link in your sig always gave me error 404 Not sure if it's just me.

 

[stella polaris]

What temperature do you have were you are working? Syria can be cold. If in a unheated area things go way slower.

 

[Yaz]

What temperature do you have were you are working? Syria can be cold. If in a unheated area things go way slower.

Yup, my bad. I should've mentioned that too. They are outside and the temp is fluctuating I'd say between 5 - 20 degrees c (41 - 68 F)

I understand the going slower part but is it to the extent of 10 days and only going backwards. If the solution stayed light green (CuCl2) and going very slow I would've concluded that it is the temp.

Thank you for pointing that out!

 

[g_axelsson]

I only called it AP because that's what I see people mostly use, and I don't have any copper chloride to start with. I do understand it's a CuCl/CuCl2 etching process.

Just so you know, I didn't criticize you, it was more of a general statement that too many people calls it AP just because it's a catchy name. Many newbies then erroneous think that you need peroxide to get it to run.

By the way, welcome to the forum. Always nice to see new members.

Ps: The goldrefiningwiki link in your sig always gave me error 404 Not sure if it's just me.

No, it's not just you. I had a server crash a year ago and restoring that has had a low priority. 2020 was a roller coaster and restoring that site is probably going to take a while. Meanwhile, you can find it on archive.org, https://web.archive.org/web/20181216121014/http://goldrefiningwiki.com/mediawiki/index.php/Main_Page

Göran

 

[Yaz]

By the way, welcome to the forum. Always nice to see new members.

Thank you, it's an awesome forum, plenty of great and helpful people with a huge wealth of information. Glad to be here!

Meanwhile, you can find it on archive.org, https://web.archive.org/web/20181216121014/http://goldrefiningwiki.com/mediawiki/index.php/Main_Page

That will do