[barrel browner]

Not sure if I am posting in the right place but I am looking for a replacement for mercuric chloride it is used in a metal finishing formula but I am trying to replace it due to the health risks of using it.

[Arkcon]

Off hand, this doesn't sound trivial.  But we can try, if you tell us a little bit more about the process -- its name, for instance.  And what the mercuric chloride does.  If its purpose is to provide a surface of elemental mercury for the next step, then it may be hard to replicate.  But if its a polishing compound, it may be much easier to substitute.

[barrel browner]

Hi I finish gun barrels using a rusting process, the gun barrels made years ago were made of iron and steel twisted together and when coated with the rusting solution it would bring out a pattern on the barrels as the solution would attack one metal more than the other, the solution is made up of Ferric chloride solution, acid and Pure alcohol the old formula worked well with the mercuric in but I was advised that it was not safe to use this as it is very poisonous ? I tried using Ammonium Chloride but that did not work, I know very little about chemicals but I would say the mercuric gave the barrel a good even covering of rust and helped produce a darker finish. thank you in advance for any help. 

[Archer]

So is the formula a mixtrue of ferric and mercuric chloride, an acid and an alcohol?

It sounds to me that you need something which will preferentially reduce in the presence of elemental iron. Ammonium chloride won't do this.

You could try copper (II) chloride as this is slightly higher up the reactivity series relative to mercury but still below iron, or silver chloride which is slightly lower in reactivity than mercury.

This is the best I can offer, I am not an inorganic chemist so others may be better able to help you.

[barrel browner]

Yes it is a mixture of those chemicals with water the idea is to have a weak rusting formula that brings up the pattern on the barrel but not aggressive enough to pit the metal, the solution is put on morning and evening and scratched of with fine wire wool. one picture is a finished barrel the other has had its first coat, thank you for your help

[curiouscat]

Yes it is a mixture of those chemicals with water the idea is to have a weak rusting formula that brings up the pattern on the barrel but not aggressive enough to pit the metal, the solution is put on morning and evening and scratched of with fine wire wool. one picture is a finished barrel the other has had its first coat, thank you for your help

No advise from me, but your work does look very awesome! Nice work there!