Removing solder (tin and lead) from sterling silver

[wct0415]

This question comes from an old post with using sodium hydroxide (lye) and hydrogen peroxide to dissolve lead and tin only.

I am dealing with some Sterling silver knives where the stainless steel blade have been soldered in place
I have removed the blade with heat to melt the solder and allow the blade to fall out and opened the hollow handle with snips to access the inside of the handles.

As best as I have determined I can dissolve the tin/lead with a solution of 50% NaOH with small addition of 30% H2O2. Since this is a 3 year old post, has this process been improved upon or a better one developed. If still valid I have a question?

My question is this: Will this solution affect the silver in any way or can the sterling be processed with 50/50 nitric and H2O as usual. I have also read in Hokes book (pg 69, 70 & 71) that HCL can be used to dissolve tin and lead . Sounds like 50% NaOH with small addition of 30% H2O2 would be the best way to remove both the tin and lead. Any advise as to a better method would be greatly appreciated. Still trying to learn before jumping in with both feet.

 

[goldsilverpro]

Soldering and brazing are something I know little about. However, I do have questions about this. For those that know, can stainless steel be soldered to sterling with Pb/Sn solder - it just doesn't sound right to me? If not Pb/Sn solder, might the solder most likely be silver solder? I know you can solder stainless with silver solder because I've done it.

As best as I have determined I can dissolve the tin/lead with a solution of 50% NaOH with small addition of 30% H2O2

Does this mean you've tried it and it works or does it mean you've determined that it will work by reading about it?

 

[qst42know]

This didn't ring true with me either but:

Joining Processes
Soldering Stainless steel can be soldered using the conventional lead—tin solders but the bond strength is often poor as is the colour match. Better results are often obtained by using the silver-bearing soft solders. The silver—tin alloys with approximately 5% silver are particularly useful especially with the stainless steel holloware.

Johnson Matthey no less.

http://www.jm-metaljoining.com/pdfs-uploaded/Joining%20Stainless%20Steel.pdf

 

[wct0415]

I have not tried it yet and I have not tested the solder as to its content or makeup.
All I have done is heated it up until I could shake the blade out of the handle. I still have the solder and will be doing a silver test on it as soon as I can make up a solution for testing.
Last night I did try to process 1 small section of one of the pieces in nitric and H2O and it was working for a period of time then got coated over with a substance that seemed to stop the process. From what I have read this is most likely lead that has coated over the silver. Not sure what to do with it from here other than try to remove the solder covering the neck where the blade was soldered.

 

[wct0415]

So I guess from the lack of any corrections or maybe try this or that, I must be on the right track on my original post. I know this is summer and everyone is probably out enjoying the nice weather except here in the NW, but I thank those that gave me more food for thought.
Enjoy

 

[element47]

You can solder these metals if you use an acid flux. I would be skeptical that a food item would use such a flux, however. Seeing it would be believing it, I guess.

This could be an instance where if the steel blade is indeed soldered at a small area at the open end of the handle, an executive decision might be made to cut out and discard the soldered area if it is so small. You might cost yourself 1-2-3 grams of sterling times the number of knives you wish to process and I appreciate that could be roughly $3 of value worst case, but it also might eliminate the need to use some chemicals which after all, aren't free. I myself have not encountered stainless blade/sterling handle knives where the two metals were soldered together, and I've taken apart well over 100+ of them. So what I am saying is if you have a load of knives and this soldered-together thing is only on 6 of them, you might just cut the soldered part of the handle away, lose $20, and eliminate needing possibly more than $20 worth of the add'l chemicals and labor req'd just to process these oddball ones.

 

[qst42know]

I have not tried it yet and I have not tested the solder as to its content or makeup.
All I have done is heated it up until I could shake the blade out of the handle. I still have the solder and will be doing a silver test on it as soon as I can make up a solution for testing.
Last night I did try to process 1 small section of one of the pieces in nitric and H2O and it was working for a period of time then got coated over with a substance that seemed to stop the process. From what I have read this is most likely lead that has coated over the silver. Not sure what to do with it from here other than try to remove the solder covering the neck where the blade was soldered.

Are you using technical grade nitric?

 

[wct0415]

No I am using 68-70% Reagent grade. I am doing a couple tests on the solder that was removed with HCL and heat, seems to be doing a good job of dissolving the solder and leaving a black powder in the bottom.
Two tests one with just the solder and the other with a small section (maybe 1 - 11/2 grams) with solder on the Ag to see how it reacts in either sample. I am not seeing yet in either of my samples any of the signs of lead in the solder so I need to retract my prior statements of lead in the solder, this would be a tin/silver solder. From the looks of it I am producing a stannous chloride solution with just the solder. Will do a test of that as soon as I possibly can.
After this I will try the solution of sodium hydroxide (lye) and hydrogen peroxide to remove solder.

Bill

 

[Goldfinger4]

H2O2 will oxidize silver to silver oxide but you won't lose any silver.
Why do you want to remove the tin? Don't you want to refine the silver?
And H2O2 is expensive.. and you need masses because it decomposes at contact with silver and copper really fast (dangerous).

 

[qst42know]

If the percentage of solder is small you could just proceed with the nitric. It wouldn't be the first time soft solder showed up where it wasn't expected.

Or the soldered portion could be cut off and cupeled with a torch.

It needn't be a big problem unless you have a lot of it.

 

[skippy]

I came across this post, and thought I would add my 2cents - the solder is not necessarily a perfect solder joint. I find the silver can often be still peeled away from the solder - the solder is used to bed the tang of the knife into the handle. I think it was repair technique. A bunch of knives I had were done like this because, I believe, at some point carbon steel blades were replaced with stainless and whoever did that set them in the solder bed. The need for a solder bond is likely minimal, and stainless can be soldered, I did it a long time ago and I believe I used hcl to dissolve the oxide coat, followed by rosin flux to coat the clean metal and solder as usual.

This question comes from an old post with using sodium hydroxide (lye) and hydrogen peroxide to dissolve lead and tin only.

I am dealing with some Sterling silver knives where the stainless steel blade have been soldered in place
I have removed the blade with heat to melt the solder and allow the blade to fall out and opened the hollow handle with snips to access the inside of the handles.

As best as I have determined I can dissolve the tin/lead with a solution of 50% NaOH with small addition of 30% H2O2. Since this is a 3 year old post, has this process been improved upon or a better one developed. If still valid I have a question?

My question is this: Will this solution affect the silver in any way or can the sterling be processed with 50/50 nitric and H2O as usual. I have also read in Hokes book (pg 69, 70 & 71) that HCL can be used to dissolve tin and lead . Sounds like 50% NaOH with small addition of 30% H2O2 would be the best way to remove both the tin and lead. Any advise as to a better method would be greatly appreciated. Still trying to learn before jumping in with both feet.

 

[Alentia]

It is quite interesting, how "removal of tin and lead" subject turned into possibility of soldering Tin and Lead to SS.

I have the same issue with some leftovers from knives. Silver adhered to Lead and possibly bit of Tin. This is they they did knives in 1920-60s mainly in europe.

I have tried in Citric Acid + H2O2 = takes way too long and too little. Now I have it soaking in HCl. Not sure if I have to add H2O2...