[nicamarvin]

I’ve been researching old patents(dating back to 1870) Silvering Mirrors and Stannous chloride(SnCI2) has been used exclusively to seed the surface of the glass with Sn2+ so 2Ag+ is reduced to pure Ag(Sn2+ + 2CI- + 2Ag+ + 2NO3- ). The only other reference found was the use of Stannic Chloride(SnCI4) but was for comparison and it was found to be inferior to SnCI2(X-ray photoelectron spectroscopy Test)

I myself as a curious mind have tested other reactive metal salts(chlorides) like Zinc, Magnesium and even Sodium Chloride all of them have proven to be as effective as Stannous chloride salts in same concentration(about 3 grams, 10ml HCI per liter of Di Water), but I am not sure how this is happening, how would Zinc Chloride as sensitizer reduce Silver Nitrate? Can anyone help me wright an equation if there even one?
ZnCl2 + H2O = Zn2+ + 2CI-
(Zn2+ + 2CI-) + (2Ag+ + 2NO3-)
Zn4+? I have search and Zinc does not have a 4+ oxidation state, so am lost here.

Would Zn2+ be limited at reducing Silver Nitrate only? Or would other precious metal be possible(see US Patent US2762714 A, filed on 1952)

[nicamarvin]

Would also like to add that I am working on alternative Sensitizer/Activator solutions for Electroless Nickel plating, I understand that numerous attempts and research has been done on the subject but so far the go to solutions are Tin-Palladium but palladium is quite expensive and I believe that by starting with a reliable substitute to Tin(Stannous chloride) would be fundamental in finding a Tin-Palladium cost effective substitute, In min mind I have Zinc-Cobalt as substitute(Zinc Chloride Sensitizer/ Cobalt Chloride Activator) and I will be testing this very soon.

[Enthalpy]

Hi nicamarvin,

[...] I have tested other reactive metal salts(chlorides) like Zinc, Magnesium and even Sodium Chloride all of them have proven to be as effective as Stannous chloride salts [...]

Did you also check without any sensitizer, just to be sure that they bring something under the conditions you use?

[nicamarvin]

without the Sensitizer no metalization occours on the surface.

[nicamarvin]

I just really wanted to know how to balance the equation (Zn2+ + 2CI-) + (2Ag+ + 2NO3-) and if I can't really get an definite answer in a chemical forum, then I guess I am hopeless..LOL..

[Enthalpy]

Nice, if you have found other sensitizers as efficient and more convenient than the stannous. Chemical silvering is a little bit outdated, but It's still done sometimes by hobbyists for microwave circuits.

What reaction? If the sensitizer acts as a catalysts, there will be no reaction equation as simple as a redox. Reactions at surfaces are complicated anyway: they depend not only on the species, but also on how these fit at the interfaces.

Is you process the usual reduction of the nitrate by an aldehyde?

[nicamarvin]

What I do is an advanced form of Tollen’s reagent but without the heat involved, it is now called “Spray On Chrome” but I am moving away from it and developing Spray On Copper which is less expensive than Silver, specially when a copper or gold(gold tint) are need it, I am also working on a electroless Nickel for plastic surfaces that will eventually be modified to be sprayed for larger surfaces.
The process is basically the same, sensitized surface for silver(Stannous chloride or in my case zinc or Magnesium Chloride), but for Copper or Nickel the sensitizer is then followed up with an “Activator” which is made of Palladium Chloride(.5 grams per litter of Di Water) With copper I have substituted Palladium with Silver Nitrate(.5 grams per liter of Di Water) but Silver is not catalytic to the Electroless Nickel(Nickel sulfate, Sodium Hypophosphite) it appears that since Tin is less reactive than Nickel, Cobalt and Iron, it can only be used as sensitizer with precious metals as activators(Silver, gold, palladium, rhodium), so what I am trying to accomplish is the following, to find a rather reactive sensitizer that will seed the surface of the plastic  article with positive atoms(Zn2+) that can reduce a less reactive metal that can start a catalytic reaction with the Nickel or Cobalt electroless solution, Nickel and Cobalt are themselves catalytic to each other, maybe Zinc Chloride Sensitizer followed by a Iron/Nickel/Cobalt chloride Activator? I have ordered all of the need it chemicals, I will be posting the results when I get them.

Spray On Chrome(Spray On Silver really, advanced Tollen's Reagent).
https://www.youtube.com/watch?v=VN_AnVpjs2A

Spray On Copper(Advanced Benedict's Reagent)
https://www.youtube.com/watch?v=WnZ9hgEfw88

[Arkcon]

I just really wanted to know how to balance the equation (Zn2+ + 2CI-) + (2Ag+ + 2NO3-) and if I can't really get an definite answer in a chemical forum, then I guess I am hopeless..LOL..

This is a red-ox reaction, and we can definitely crack it.  But why?  It doesn't answer your jargon:  Sensitizer/Activator/Brightener are all jargon for sometimes proprietary agents used to alter the plating process.  I know some of them, but not all, and I used to work for a plating bath company.  Seriously, there was no reason for them to tell me their trade secrets just because I was analyzing their products.

[Borek]

Actually I see no redox to happen in the Zn²⁺/Cl^-/Ag⁺/NO₃^- mixture. The only thing I am sure of is a precipitation.

[nicamarvin]

This is a red-ox reaction, and we can definitely crack it.  But why?  It doesn't answer your jargon:  Sensitizer/Activator/Brightener are all jargon for sometimes proprietary agents used to alter the plating process

Finding the Answer for the Jargon is not really my aim as they have been used for such a long time that the term Sensitizer and Activator is almost guaranteed to include Stannous Chloride as sensitizer and Palladium Chloride combo for the metallization of non conductive surfaces, I was just trying understand the science behind the reaction and by doing that maybe find alternatives.
Sn2+ ions that are absorbed and left on the surface of the piece after the sensitizer immersion and later rinse will reduce the Pd2+ ions on the Palladium chloride activator(PdCI), to elemental Palladium which leaves a catalytic surface that will allow the piece to be coated with nickel.

While this process has been proven to be very effective at least in the last half century, one gram of palladium is quite expensive, other precious metals have been proven to work well, but as precious metals, their price is expensive too, but I believe that only precious metals have been tested because no other sensitizer(Stannous Chloride) has been used before and due to Tin location on the metal reactivity series no other metals that are proven to be catalytic to electroless nickel have been tested as an “Activator”, non-precious Metals that are catalytic to electroless nickel(that will initiate the nickel deposition) are only a few, Iron, Nickel and Cobalt.

My Theory is that a Zinc Chloride based sensitizer(proven by me to be effective for Silvering) will reduce a Cobalt Chloride base activator to elemental Cobalt and the surface will prove to be catalytic to electroless nickel, in any case I have made the necessary order for the test procedures(nickel/cobalt electroless solution and Stannous/Palladium activator, Zinc and Cobalt chloride), I will post my findings here when I get them.

[ehsan.chch]

Hello
I also use palladium chloride and the excellent reaction is done
But palladium chloride is very expensive. I also use silver chloride, but it is also relatively expensive
If you find that you have found a good alternative to this, please let me know.

Thanks