[daginhun]

Can you tell me please, that what's the reaction between:
nitric acid and ammonium thiocyanate
sulfuric acid and ammonium thiocyanate
silver chloride and ammonium thiocyanate
sodium thiosulphate and ammonium thiocyanate
Is any danger for health in any of this reactions, like cyanide gas?

[Schrödinger]

Please read Forum Rules. You need to show us your attempts first.

[daginhun]

ohh, sorry. I need to know it for electroplating.

[Arkcon]

OK.  So, if these are common electroplating reagent, and you're not doing an undergraduate problem, then why are considering mixing them at random?  What is your application, and what recipes for chemical plating do you know, and how does your potential application mesh with known procedures?  As you've gone through your applications, so far, have you learned basic chemistry, that you can apply, to solve this problem for yourself, and other potential ones, that may come up, as you develop new ideas for things to try?

[daginhun]

Need to clean the copper in nitric acid and sulfuric acid, then pretreatment (fer better adhesion) in ammonium thiocyanate, then silver plate.
The bath formula is this:
silver chloride 30-50g/l
sodium thiosulphate 500g/l
sodium or potassium metabisulphate 30g/l
for pH: sodium bisulphte or hydroxide
0,5A/dm2
So I asked those reactions (in the fist post), because I would like to know, that is there any dander, if I can't wash the copper normally between these steps. Or from AgCl after plating and Cl can be "free and react with ammonium thiocyanate?

[Arkcon]

Generally, between the cleaning, pickling, pre-treatment and various plating steps, a very through distilled water wash is performed.  This is to avoid mixing the solutions, even slightly.  Not necessarily for some dangerous reaction, but to keep the individual baths from becoming contaminated with each other, and degrading the smoothness of the final plating by competing reactions.

[daginhun]

Thank you! So for example, If accidentally ammonium thiocyanate drops can splash in to one of those bath what you can see above, I wont be in danger, because none of the chemicals can form dangerous gases.

[Arkcon]

Thank you! So for example, If accidentally ammonium thiocyanate drops can splash in to one of those bath what you can see above, I wont be in danger, because none of the chemicals can form dangerous gases.

Sorry.  I can make no such guarantee.  I am not sure.  You might try asking a plating expert, but they will tell you what I'm going to tell you -- you don't accomplish anything productive by being sloppy, so no one goes out of their way to be sloppy, just to test if its health hazardous.  All chemicals purchased come with an MSDS available, it might specify some well known, very obvious, specifically bad, things to mix with a particular chemical.

[eazye1334]

Unfortunately, I don't think safety is your only problem here.

Adding ammonium thiocyanate to the plating steps isn't going to do anything except corrode the hell out of your copper. Silver on copper plating is notoriusly difficult due to immersion deposition which causes your poor adhesion. And to top it all off, you're using a cyanide-free bath, meaning your adhesion is even worse.

In all reality, I don't see any way you're going to improve anything without a silver strike bath or adding a nickel layer first. For home plating of silver, electroless plating is really your only safe option.

Also, ammonium thiocyanate is not friendly with strong acids, aka your nitric acid in your cleaning step.

[daginhun]

Do you think after when I polished and cleaned the copper plate, instead of ammonium thiocyanate better to use nickel as a pretreatment?
After nickel plating what to do with the plate? Just need to wash it and then do then silver plating?

[eazye1334]

I would suggest that if you were doing cyanide silver plating, but non-cyanide silver has adhesion problems to nickel as well. It also would likely cause a yellowish-silver deposit instead of the silver you're probably looking for. Silver is just really difficult to plate.

Unfortunately, I really don't know what will work for you in this instance as I don't know very much about non-cyanide silver plating, so I don't even have any good suggestions for you. The only thing I can tell you to do is check out Finishing.com and try poking around in there for something, or maybe even send in your own question.