daginhun

Topic: no cyanide silver plating over copper

Hi,
I'm an artist, so I don't have silver plating background. I would like to start silver plating at home. I need to silver plate, copper plates, which are polished. After silver plating I need to polish the surface to get a mirror like silver.
I want to use silver bath which is not contains cyanide. I was searching on the internet and I found 2 possible bath solutions:

1.)
Silver chloride 30-50g/l
Sodium thiosulphate 500g/l
Sodium metabisulphate 30g/l
for pH: sodium bisulphate
0,5A/dm2

2.)
AgCl
KI
temperature: 30C

I couldn't find much informations about the second one, except the silver will be a little bit yellow, but no adhesion problem. Do you know anything else about this? How much (g) from AgCl and KI I need to use in the bath? Any experience with this?

The problem is with the first one is the poor adhesion. How to solve this problem?
Ammonium thiocyanate? In other forums I didn't get clear answer about safety and adhesion questions, so maybe not.
Then I found, that I can use nickel plating first as a pretreatment. I was keep reading about nickel plating pretreatments and I saw, I still will get poor adhesion just with nickel. I saw it somewhere, that after nickel plating, I need to use copper strike for good adhesion and then silver plating.
But why I can't use copper strike just simply on the copper plate, so don't need to nickel plate???
Do you have any other ideals as a pretreatment?
What can be the process?: polish the copper-clean it- washing-nickel plating- washing- copper plating-washing- silver plating? OR polish copper-clean-washing-copper plating/strike-washing-silver plating? Can be good as well? Can you offer any NO cyanide copper strike solution?

Last edited by daginhun (01/12/2013 - 08:44 AM)

daginhun

Re: no cyanide silver plating over copper

Sorry, I forgot to write in the process. After when I polished the copper plate, the "cleaning" step is in the solution of nitric acid and sulfuric acid and then....need some help??

daginhun

Re: no cyanide silver plating over copper


I was thinking about silver succinimide based bath as well, but I think to buy silver succinimide is difficult and really expensive.
I'm still interest to solve the problem what I posted in the first post!!! Adhesion, pretreatment, silver strike, no cyanide...

DustinGebhardt

Re: no cyanide silver plating over copper

The second
sequence should be sufficient to get good adhesion. I'm not very familiar with non-cyanide silver plating baths, so I can't answer any questions regarding that. I will also mention that your cleaning step will probably not be adequate. If you are polishing using a fat-based compound, you will need to you some sort of alkaline, heated cleaner. After the hot alkaline cleaner, you can rinse the part and then go into your acid bath. Rinse after that, then go into your copper strike/plate. If, after the acid bath, your part shows water break or beading, the part is not sufficiently clean for plating and the cleaning process must be started over again.

-Dustin Gebhardt, CEF

Advanced Manufacturing/Finishing Engineer

Moen

Sanford, NC

daginhun

Re: no cyanide silver plating over copper

Hi,
Thank you for your answer!
Yes, after when I posted this message, I was still searching and I decided to try the following process:
-Mirror like polish on copper plate
-wash it and dry
- wash the plate in acetone and then in water
-in sulfuric acid and then wash it again (a few days earlier I heard about the test: copper surface need to hold the for 30 sec. If not, need to repeat the previous step)
-silver plate in AgCl KI based formula. After plating if it will be too yellow after polishing, this step will be just a silver strike, if not I can stop in here)
-if the previous step is too yellow, then I will silver plate with the thiosulfate based bath, because between silver and silver the adhesion will be good (is it?).

What do you think about this? Instead of acetone can you offer hot alkaline cleaner what you mentioned, or acetone will be fine as well?

DustinGebhardt

Re: no cyanide silver plating over copper

For a hot alkaline cleaner, you can try using a solution of sodium carbonate or sodium bicarbonate, along with some normal dishwashing soap.  Heat it to 150-180'F and it should clean away most buffing compounds.

-Dustin Gebhardt, CEF

Advanced Manufacturing/Finishing Engineer

Moen

Sanford, NC