Gold hidden under paint

[kurtak]

It gets really quite hot. A glass beaker or corningware may be a better choice but I don't have either yet.

NaOH is corrosive to glass - it will etch beakers & corning ware - better to use plastic bucket, cast iron pot or stainless pot

here is a picture of a beaker that has been etched by NaOH :arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=47&t=21342&p=220281&hilit=etch+glass#p220316

Edit; Do NOT use NaOH in an aluminum pot :!:

Kurt

 

[necromancer]

Thank you Geo I will surely keep that in mind when choosing.

However I had very hardly obtained P marked corning ware and I managed to crack it within few days. I did place a 1/3 full beaker inside the empty corningware and then put on top of my electric burner, I did wanted to evaporate the solution down so I went to 80°C (temp inside the beaker) but after quite few minutes the, supposedly pyroceramic, broke. I would image it did happen because the cornigware was empty, silly me, and by putting water (under the main liquor level) everything would have gone ok.

Hey necromancer, thank you very much for your offer. I'll keep looking while keeping your offer in mind. Really, really appreciated.
I believe there is an issue with the arrows in your photos as none of them are pointing to gold plated areas. I normally scratch the solder mask with a steel blade to really see if the underneath plating propagate all over the surface area or it's just few dots here and there.

you can see the scratched area in the middle of the photo. its a nicely plated area. i will photo after removing the mask

 

[MarcoP]

I see it now, thanks.
Last time I've used 30% lye (20% wasn't enough in my circumstances) to remove the solder mask, the gold plating tarnished. Not sure what happen there but I don't believe I lost any.

 

[Anonymous]

Tarnished Marco? In what way?

 

[MarcoP]

I should have taken a picture! It only happened on wide plating areas find in LCD boards or what I believed to be a very thin plating not used in contact points. If I properly recall the plating darkened to a dark brown color. May the term I've used, tarnished, isn't the proper one but it was like it was cooked, or burned, by the lye.

I was still able to recover 1.3gr of double refined gold powder out of 150 ram sticks and many other boards with tarnished plated area due the lye treatment. Maybe I cooked them for too long when instead a couple of minutes were sufficient. However I still believe was just a visual effect without any loss. Hope I'm right here.

I didn't post my issue, even if singular, because next time I wanted to try boiling them for a couple of minutes as instructed without exaggerating.

 

[GotTheBug]

I just noticed the same thing, and am believing some gold was removed by the naoh and h2o2 mix. If so, how can I recover gold from NaOH solution?

 

[Barren Realms 007]

I just noticed the same thing, and am believing some gold was removed by the naoh and h2o2 mix. If so, how can I recover gold from NaOH solution?

If it will not settle to the bottom of your container dilute the solution and it should settle to the bottom then you can remove the solution and clean the foils of the rest or the residue of the solution.

 

[Beirdo]

One note to be careful about: on most circuit boards that I've seen, what is under the soldermask is copper. Typically, the gold plating is applied *after* the solder mask. There are, of course, some exceptions, but I would not be expecting to find much gold buried under solder mask in most circuit boards. Gold is usually plated onto things that are connectors primarily, and other than a few RF circuits, there is little advantage to having a gold surface, especially if it isn't exposed. The gold is there to keep the connector's contacts from corroding, basically.

 

[MarcoP]

I just noticed the same thing, and am believing some gold was removed by the naoh and h2o2 mix. If so, how can I recover gold from NaOH solution?

I didn't use any H2O2, but if you have a touch stone you could easily test if gold was removed or just darkened by the lye. By next time I will probably have a touch stone with all testing solutions, day after day I see how easy certain things could be with one.

 

[GotTheBug]

I had a few boards, cell phone and old sound blaster (which was nice since it was full plate on both sides), and thought it was a good idea to "hurry things up" by adding h2o2. I still have the solution, so will dilute it and play a bit just to see if any went into solution. I've already run the slime in AR after rinsing well and nothing there, so we will see. Of course, it is also possible that the plating was simply discolored by the lye. This was my first go with hot lye, since I was basically scared. All went very well, and no permanent badges for my efforts!

Now is where I take another moment to thank you guys, again....

Paul.

 

[jason_recliner]

It gets really quite hot. A glass beaker or corningware may be a better choice but I don't have either yet.

NaOH is corrosive to glass - it will etch beakers & corning ware - better to use plastic bucket, cast iron pot or stainless pot

here is a picture of a beaker that has been etched by NaOH :arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=47&t=21342&p=220281&hilit=etch+glass#p220316

Edit; Do NOT use NaOH in an aluminum pot :!:

Kurt

Good to know. Thank you for the correction Kurt.

 

[patnor1011]

For me personally amount of gold to be recovered from odd soundblaster or RAM stick does not warrant dangers involved when working with hot NaOH. No matter how many of soundblaster cards I will have, it will take the same amount of danger be it one or 20.
I stopped chasing cents, I was many times losing dollars in the process. I will leave that minuscule amount of gold to copper smelter to recover. You may get much more for depopulated board with solder mask on (depend on where you are located) than gold recovered from this minus supplies and time involved.