Plating Standards to Prevent Tarnishing on Gold-Plated Silver and Brass
July 1, 2010
I work for a jewelry company that buys from overseas factories. We have gold-plated silver and gold-plated brass products that are tarnishing, apparently due to insufficient plating and the presence of sulfur in the packaging. I have a few questions: First, is there a minimum thickness that would ensure plating didn't tarnish and lasts a long time (i.e. years)? Would this be different for gold-plated brass vs. gold-plated silver? How about rings versus pendants? Would e-coating be a good solution? I worry the coating might peel off and look odd after some time. Thanks!Mike O'Donnell
Jewelry Manager - Norwalk, Connecticut, USA
July 8, 2010
Silver, copper, and zinc will walk right through gold with time and/or temperature. You must have a diffusion barrier of nickel or palladium between the silver, and/or copper, and/or brass.
Robert H Probert|
Robert H Probert Technical Services
Garner, North Carolina
July 9, 2010
If gold is plated directly on silver, copper, brass, etc., these metals will migrate up through the gold and produce tarnish on the surface. The thicker the gold, the more time it will take but, in my experience, it will eventually happen. For this reason, an adequate thickness of nickel is commonly plated underneath the gold to act as a barrier to this migration. The gold, itself, should not tarnish unless it's of a very low karat.
I would first suspect the nickel as being too thin or not being there at all.
- Nevada, Missouri, USA
July 13, 2010
By federal code gold electroplated jewelry needs at least 7 micro-inches thickness of gold. Heavy gold plate and Vermeil must be at least 100 microinches thick. Very often jewelry made in the third world does not meet these standards. To prevent tarnish a barrier layer of nickel or palladium should be plated over brass and silver before gold plating.
July 22, 2010
I used to work for a fine jewelry Co. in Newark,NJ.
We developed and marketed 18kt gold electroplate brass jewelry with lifetime warranty. At that time there was no standard (astm,mil-spec, etc.) that met our requirements. We develop our own.
- Mays Landing, New Jersey, USA
April 7, 2012
My company in Winter Park, Florida, is often asked to gold plate mouthpieces for musical instruments. It has been my habit to silver plate the brass mouthpiece before depositing my gold. My question is this: is it acceptable by industry standards to do this? Will silver migrate into the gold layer? If it does, is that bad? I notice that manufacturers of church accessories often plate gold directly over sterling silver chalices and ciboriums, etc.. I've been doing this for thirty years and haven't had any complaints from my customers, but after a conversation with another metal finisher here in Orlando, I've been having second thoughts. Can you give me any guidance in this matter?
Thank you for your time,
owner - Winter Park, Florida, USA
A. Hi David. I may not be the best person to ask because I'm a pragmatist :-)
If a process has been working fine for you for 30 years, I wouldn't change it. Mouthpieces never get above room temperature or body temperature, so diffusion is slow. They are not soldered, so no concerns of intermetallics messing things up. They are not electronic components where ultra-low contact resistance must be guaranteed. They are not fine jewelry where the slightest off-color could be a big issue. Adding a nickel layer would be adding many potential complications.
In short, it's working for your application so don't change it ... but don't go lecturing the Orlando shop that they don't need a nickel barrier -- they probably do :-)
Ted Mooney, P.E. RET
Brick, New Jersey
A. I was just looking at a piece of 60+ year old Tiffany Vermeil.
It still looks like new.
Will silver migrate through gold plating if there is no nickel barrier? Yes. But if the gold plating is done well and thick enough, it won't happen in a lifetime.
I'm guessing, and it's only a guess, that at ambient temperature, the migration of silver through gold is no more than a few microns per year, so if you're plating, say 50+ microns of gold, your original customer will never have a complaint.
Jeffrey Holmes, CEF|
- Spartanburg, South Carolina
June 13, 2013
Q. We recently started manufacturing brass jewelry. And a lot of our pieces need to be gold & rhodium plated. We are seeing a lot of gold plating starting to tarnish within one week of plating. The rhodium plating remains fine. What could be the reason? We have the following plating process:
- Polished brass jewelry is cleaned.
- Brass jewelry is plated with Alkaline copper
- Pieces are then plated with Acid copper. This plating is thick micron plating.
- Pieces are then plated in silver strike solution
- Pieces are plated with silver micron (cyanide based)
- Pieces are then plated with palladium (flash)
- Then finally gold plated (flash)
- Lastly rhodium plated.
Thanks and I look forward to feedback.
- Mumbai, INDIA
^- Privately contact this inquirer -^
June 19, 2013
A. Hi Pushpak,
Possible causes are:
1. Gold bath contamination (metallic and/or organic).
2. Poor water rinsing after gold plating.
3. Gold deposit porosity.
4. Storage environment.
5. Metal migration from substrate.