Plating gold directly onto brass

A. Hi Phancheata

Please remember that it takes very few rejects to convert a cost reduction program into a program that actually increases costs, which appears to be the situation here. Skipping the second nickel plating step, thereby plating gold directly onto brass, is usually considered a poor idea as you will read repeatedly on this page.

However, I'm not understanding why you need to do the first nickel plating. Why can't you just plate after fabrication?

Luck & Regards,


Ted Mooney, P.E. RET
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finishing.com - Pine Beach, New Jersey
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A. Yes, you need to do nickel plating on your brass prior to gold plating. Nickel works as an anti-diffusion layer between brass and gold. Copper and zinc will migrate to the top of the gold surface from bottom and get oxidized and black once they contact the air without having the brass nickel plated. 10-20 microns of nickel will be good enough.

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A. Hi, Sunny. I think you have been advised correctly. The gold and brass do slowly diffuse together if there is not a barrier layer of nickel between them. While this may not be a major problem at room temperature with thick gold plating, it may be with half-micron thick plating.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hello,

In fact, a barrier layer shall be added between brass and gold.

Onto house-goods, we put a 5 microns bright nickel layer to avoid the problem of Copper diffusion into gold layer.

But, considering the new politics concerning "nickel-free processes" for jewelry, we have replaced the nickel barrier by a white bronze layer (5 microns) for the parts in permanent contact with skin.

Hope it can help you.

A. Hi,

You can always plate on top of Bronze, I think you have some problem with the chemistry of White bronze.

A. Hi Katie.

Neither white gold nor rhodium will turn your finger green, but brass will. So if the plating is good and heavy and free of porosity you will be okay until it wears thin.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hi cousin Sara. Unfortunately it is difficult to tell the quality of jewelry just from a seller's claims because their intention isn't really to inform you, but to induce you to buy. Yes, 22 kt gold plated jewelry is probably non-tarnish, and it can be fine, but the thicker the gold plating the better. If they don't tell you the thickness, it's probably not very thick at all. Good quality costume jewelry used to be one micron thick (micron gold), but these days finding stuff thicker than 0.1 micron can be difficult. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hello Thelma, the gold over brass will tarnish. The brass will migrate into the gold plated layer because there is no barrier plate. For the Rhodium plated, it would depend on the thickness of the rhodium plating. Rhodium is one of the hardest finishes as plated. Depending on how often the piece is worn would be directly related to the rhodium wearing off. The rhodium finish would hold up much longer than gold over brass.

A. I have had bad luck with having my hand made brass Engineers ring professionally gold plated. I even suggested to them to nickel plate it first. They didn't and the gold plating wore off in a matter of months. Definitely nickel plate first. Good luck.

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A. Hi Oi. As noted earlier, trying to judge the longevity of a finish from the vendor's sales pap is nearly hopeless but I'll pick whatever is behind door "2".

Door 1: 0.03 mil is .76 microns, which is probably very reasonable today for costume jewelry. If it's a broach, it will probably last quite a long time; but if it's a ring, it probably won't last long (rings get a huge amount of wear).

Although you don't know the thickness of the white gold (or possibly actually rhodium) plating on the sterling silver item, and it is impossible to predict it's longevity, the simple fact that it's made of sterling silver rather than brass, so is more costly, is a good indication that it's probably higher quality. And with the base being silver, you'll never see a yellow color showing through.  🙂

Luck & Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hi Koby. As long as it remains "spent", nickel plating followed by gold plating sounds fine. But I'd be leery of firing cartridge cases with nickel and gold plating.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hi Jack. Some would say to plate it with cobalt, but others suspect that cobalt is so similar to nickel that it's likely to have similar, just less publicized, issues. So white bronze plating or palladium plating is probably the best answer. There are several proprietary brands of white bronze plating processes available.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hi Gale. I'm no ammunition/firearms expert so I can't comment on potential safety issues with dimensional clearances, friction, cold welding in the barrel or clip, embrittlement of the casing and possibility of explosion, etc. I'm simply saying that gunpowder-charged bullets are precision engineered & carefully tested devices -- and I'd be careful of willy-nilly alterations, especially amateur attempts at activating & electroplating because amateurs, almost by definition, often do a poor job and often don't understand all of the consequences of things.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Gold plating brass is no problem and you definitely need a nickel undercoat.
Some brass cases come already nickel plated and there is a problem. Nickel passivates and has to be activated before it can be plated or adhesion will be very poor. It is much simpler to start with brass cases and nickel plate immediately with gold. This means nickel plate, rinse, gold plate not allowing the parts to dry out between.

I assume you are intending to plate the cases not the heads unless you are looking for low cost vampire ammo.

A. Hi Edward. Even if you know exactly what you've got, perfect cosmetic repairs are difficult. In this case I suspect that the lock had a thin layer of gold electroplating followed by some sort of clear lacquer. These finishes are usually mass-produced, with hundreds of parts simultaneously processed. I think the labor cost of re-plating and re-lacquering a single piece will be prohibitive, and that you will find it impractical to do in situ anyway.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hi Katrina. Unfortunately, ad copy is designed to entice you to buy, not to technically inform you about the durability of the item. There are dozens of variables, and no practical way for a consumer to know the quality & longevity of the items they are buying except by relying on the integrity of the brand name and of the store.

Sorry, but I think that's just the way it is :-(

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Serena:
The durability of wear of your rose gold plate should be about the same over either since the plate is the same thickness. Rose gold already contains some copper so the substrate doesn't matter regarding tarnish.

A. Either nickel or palladium will stop diffusion from the under layer, however, nickel is irritating to some people's skin and that is why palladium is usually preferred.

A. Hi Katharine,

I have seen palladium fail as a barrier, maybe because it was too thin. Regardless you should be able to get good results with gold plating over brushed and satin surface finishes as well as highly polished surfaces.

A. Hello Ruby, a palladium undercoating would be expensive, especially if you are dealing with plated jewelry. Check into white bronze as a barrier between the brass and gold. Six microns of the white bronze should be sufficient. Gold thickness on plated jewelry is normally very thin (10 microinches.) If you want quality, 2 micron gold thickness is the way to go as the finish will last longer than a flash plate. Use a hard acid gold which will give you better wear resistance. Keep in mind that with a barrier plate the gold color will be much different than it is with a brass substrate. Color matching will have to be done. With the added process and thicker gold deposit check your bottom line.

A. Hello, because brass is the underlying metal and there is no barrier plate (to prevent migration of the brass into the gold) it would actually depend on the thickness of the rose gold plate on how fast it will tarnish. Normally with this type of jewelry the gold plating is very thin. For cleaning, I like to use juice from real lemons. White vinegar ⇦ in bulk on eBay or Amazon [affil link] works too. You can soak it first and then use a soft cloth to clean it better.

A. Hello Jennifer, you will be much better off with gold filled, as the gold layer is much thicker than electroplated gold. By standard, gold filled has to be a minimum of 5% gold by weight. The gold layer is bonded to the jewelry by heat and pressure. I wouldn't be concerned about tarnishing that much. A standard jewelry cleaner would be fine for normal cleaning.

A. Hi Robert. Chrome plating by itself is not a decorative finish; you need nickel-chrome -- in other words an underlayer of nickel plating anyway.

7 microns is, to my understanding, the thickness of gold used on the finest heirloom watches these days. Even 2-1/2 microns would be very high quality. I'd probably go with nickel plating followed by 2-1/2 microns of precious metal. But it's a bit more complicated than that: rose gold is usually just a thin "color" layer over a thicker layer of yellow or pink gold. White gold is usually not comprised of plating with white gold, but plating with rhodium. And chrome plating is usually substantially thinner than 2-1/2 microns. Good luck.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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A. Hi Robert
Two thoughts.
A nickel barrier is so common that your supplier considers it part of the routine plating.
Do you have a means of verifying the gold thickness? And/or does your supplier certify the thickness. 5 microns of gold is an expensive spec to just take someone's word.
The kit (XRF) is expensive but without it neither you nor the supplier can guarantee the thickness.
You also need to consider that a belt buckle is a complex shape and the plating will not be of equal thickness all over.
Paying for a minimum thickness all over is expensive, as much of the part will be thicker and you will be paying for it.
I suggest that you get a sample plated and do a thickness survey and then decide what is the critical area that you need to specify.

A. Hi again. As you can see, Geoff anticipated most of your questions.

Yes, the nickel plating must be done immediately before the gold plating. Vermeil jewelry is 2-1/2 microns of gold over sterling silver; you might be able to research how it holds up. X-ray Fluorescence thickness testing machines are awfully expensive, about the price of a new car, but you can probably find a lab to do the testing on a contract basis is need be. I believe brass is probably considered to be the most durable, plateable, and practical metal for such applications. Good luck.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hi Shannon. The longevity depends primarily on the gold thickness and plating barrier. So if you don't know that, unfortunately you can't make any predictions of life regardless of the substrate.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hi Kevin. If you find such a ring it will not turn colors. But I doubt that you will. Very good costume jewelry is 1 micron, vermeil is 2-1/2 microns, the world's finest super-premium watches get about 7 microns. Few of us have heard of 20 microns since the Rockefellers and Carnegies stopped carrying pocket watches  🙂

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

Q. How long will it last?

Directly on brass, thin gold will not last very long, maybe months.


With a thin layer of nickel under, will last longer, maybe years.

But unless you know the gold thickness all bets are off.

A. Hi Gordon. A small vibratory finisher might be the easiest way to clean up old coins. The 'reverse current' process you describe sounds like a "Wood's Nickel Strike" ⇦ huh? but is commonly used on stainless steel and old nickel plating rather than on silver or copper, and I don't think it's necessary. For the very small volume of work which you are probably doing as a custom jewelry maker, the best activation may be to simply scrub with pumice, dish detergent, water & a nail brush, then rinsing before plating. Yes, bright Watts nickel plating will serve both as a barrier layer and as a bright base for shiny gold plating.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hi Gordon. I think that will probably work fine. And you're certainly welcome; glad to have you here.

Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Hello Jimmy,
Palladium is used as a barrier plate in some cases. It is more expensive to plate than nickel, but Palladium will not cause nickel itch or rash when the gold wears down and a nickel underplate is exposed. Wear resistance depends on the thickness of the gold plate and how the piece is worn, whether it be a ring, necklace or broach.
I would not go too thin on the Palladium however. You want to be sure all pores on the brass are closed. You are giving your product a good thickness of gold which will give you a nice durable product. Good Luck in your venture!