Gold plating specifications - why is plating bright vs. matte?

A. Dear Matt,
I shall try to answer to your questions as follows:
Questions:
1) Does a matte finish indicate that there may be something wrong or with the plating process that was used?
GOLD PLATING ON ITS OWN DOES NOT GIVE A BRIGHT FINISH. THE BRIGHTNESS DEPENDS UPON THE BASIC BRIGHTNESS OF THE BASE METAL. FOR THIS USUALLY A BRIGHT NICKEL/SULPHAMATE NICKEL UNDERCOAT IS GIVEN PRIOR TO GOLD PLATING. CHECK WITH your VENDOR.THERE ARE MATTE GOLD FINISHES AVAILABLE. BUT IT IS GENERALLY USED FOR DECORATIVE OR VERY SPECIFIC REQUIREMENTS.
2 Is it usually necessary to specify "bright" or "matte" finish?
YES. BUT your REQUIREMENT IS ELECTRICAL CONTACTS. THERE IS NO NEED FOR MATTE FINISH. NEVERTHELESS NO MATTER.
3) Can someone suggest a more thorough plating specification that would cover all necessary information?
MATT: You SHOULD BE CONCERNED ABOUT THE HARDNESS WHICH HAS TO BE IN RANGE 160-200HV. IF IT CONFORMS TO THIS SPEC, I DO NOT SEE ANY PROBLEM. YOUR POSTING DID NOT MENTION THIS BUT ONLY SAID "HARD GOLD"! YOU MAY PASS THIS AFTER CHECKING THE HARDNESS.
REGARDS,

A. Hi, Sankara.

It is usually faster, easier, and less expensive to do tank plating unless there is a specific reason to do brush plating. In the case of gold plating, where labor is a much smaller part of the total cost because of the high cost of gold, sending it to a plating shop may save money rather than cost money.

Regards,

"Gold Plating Technology"
by Reid & Goldie
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see a copy cheap, act fast)


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A. Hi Lewis. We appended your inquiry to an earlier thread about matte gold plating which should offer you food for thought. There probably is no bright nickel plating below the gold -- perhaps dull nickel. There might also be an ultrafine glass bead blasting. Obviously we can only talk in generalities about how such things are usually done, not how Nomos actually does it, as we must be careful to avoid crowd-sourcing industrial espionage :-)

Another thing is that various colors of gold are available for watch plating (achieved via different percentages of alloying metals).

Usually faster progress will be made towards getting helpful answers if you explain your own situation. For example, dull nickel plating or alloys with a lot of non-gold may be no problem for watch dials sealed behind crystal, whereas adopting these answers to other product lines might be highly problematical in terms of nickel leaching, tarnishing of low alloy gold, etc. There is little concern about corrosion or leaching when components are sealed in a waterproof case, but the plating on those watch hands might not fare well if exposed to the world :-)

Regards,

"Gold Plating Technology"
by Reid & Goldie
(hard to find & expensive; if you
see a copy cheap, act fast)


on eBay or

AbeBooks

or Amazon

(affil links)

A. Hi Kevin. Reid & Goldie says that KAuCl4 was considered as far back as 1845 by Elsner, but it does not otherwise address it in the whole 630-page treatise. I find no other obvious reference to gold plating from AuCl4 in my plating library and I've personally never heard of it :-(

Best of luck to you, but I think the chances of successful plating from such a solution are nil regardless of what additives you employ. Please explain what motivates you to try such a composition. Thanks.

Regards,

 Thank you ted. I figure it would be nice to have a non-cyanide solution because of the prolonged exposure side effects; it's a big industry and regulations are getting more strict against working with these chemical.

A. Hi Kevin. Not to discourage further research in any direction you wish to take it, my understanding is that gold sulfite baths are the only production-viable alternative to cyanide.

Regards,

A. Hi Kevin
I have seen gold chloride baths used in commercial refining. The deposit is very pure but the quality of the plating is rubbish.
I know of no long term effects of cyanide. At sub lethal levels, the body has several mechanisms for eliminating cyanide which is good because cyanide is present at low levels in the environment and even some foodstuffs.
In any case, plating baths based on gold potassium cyanide contain very little free cyanide.
I agree that the safety community tend to be paranoid about anything associated with the C word but this is largely based on ignorance.
We understand cyanides very well but the same cannot be said for any of the proposed alternatives.
You can find considerable factual detail at
https://www.academia.edu/10635761/Cyanides_in_Metal_Finishing_Risks_and_Alternatives

  Thank you guys.