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"Gold plating rubs right off!"





An ongoing discussion beginning back in 2009 ...

December 31, 2009

Q. Hello all,
I had some silver medallions/tags cast for making engraved bracelets, and then had some of them rhodium plated and others gold plated (18k I was told).
I had read somewhere that the plating should be 3 microns thick to be lasting but I don't know of any way to measure the layer after the process. Anyway, I started rubbing one of the gold plated medallions with a silver cleaning cloth, and the plating came off in 15-20 seconds!
Is that normal? Obviously you shouldn't clean a plated medallion with that kind of cloth, but still... I did the same thing with a gold plated brass medallion I had bought and it didn't rub off.
Q1. How can I obtain a better plating quality?
Q2. I read it depends mainly on 2 factors: the amount of gold in the bath, and the duration of the bath. What is the quantity and duration required to get a plating that is at least 1 micron thick?
Q3. Is there any way to test the quality of the plating?
Q4. Will applying some kind of coating over the plating increase it's longevity?

I really hope someone will be able to help me,
Thanks a lot

Sebastian Guy
designer - Seoul, South Korea
^


January 8, 2010

A. Dear Sebastian,
A1: You should have a method for good base metal preparation and activation of your items to be plated. Here one of the reason though not major can be of lack of adhesion but not a major reason.
A2: The amount of gold in the bath, nor the duration of the bath is not the problem in your case. It is outright cheating by your plater(if you asked him to plate 1 micron). One micron gold per 100 sq. cm (1 dm sq.) should weigh 175-178 mg. gold. The plater did only a flash plating.
A3: In your case you can use an electronic weighing machine. Wt of item (dried) before gold plating = A; wt. after plating gold(dried) = B. Wt of Gold = (B-A)=C
A4: You can have electrophoretic lacquer coat or dipping lacquer applied and backed.
Regards

t k mohan
T.K. Mohan
plating process supplier - Mumbai, India
^


simultaneous January 10, 2010

A. Sebastian,
Gold should not rub off that easily. In the jewelry plating industry 3 micron plating is virtually unheard of. As a rule, that thickness (120+ microinches) isn't even used in electronic plating. Color golds are normally a flash thickness of around 3-5 microinches. Even at this thickness the gold should not rub off that quickly as you say. It sounds to me you need a better plater. Certain factors ensure good gold plating.
A bath has to be kept in spec for the type of plating you plan to do. This includes proper gold concentration, adequate conducting salts, alloying agents (brighteners), ph (if applicable), temperature, current applied, and the purity of the bath. Dwell time is a key factor as well. If the plater dips the work in the gold bath for 5 seconds and the gold in the bath is low, the deposit will be inferior and will not last. You don't need 1 micron plating thickness for costume jewelry. If you do want that much, be prepared to pay a lot more money than you want to. Any good plating shop has the means to measure the gold thickness on a certain number of pieces per lot. Have them send gold thickness printouts with the shipment. You shouldn't have to go out and buy thickness detection equipment just because your plater is doing a shoddy job. I cannot give you exact dwell times for gold plating because gold concentration and bath efficiency are unknown.

Mark Baker
Fellow Plater - Syracuse, New York, USA
^


January 11, 2010

A. Cleaning the surface is definitely key but after that is done there may be more you can do.

Is it possible for you to strike the silver in copper and than the copper in nickel before the gold plate? Using this method, if the parts are dried after they are struck in nickel you should dip them in a 10% sulfuric acid bath for 10-15 seconds to ensure good adhesion followed by a good rinse before gold plating.

Dimitri Stath
- Oshawa, Ontario, Canada
^


January 18, 2010

A. Hi,
I would suggest you to go for an hard gold bath or for an gold forming bath to plate 3 microns, the hard gold deposit will not have a very good colour (like 23 or 24 k) but then you can have a flash of the desired colour you need.
Then a topcoat of spray or electrophoretic lacquer will help on for longer protection.

Best Regards

praveen kumar
Praveen Kumar




plating process supplier
Mumbai, India

^


sidebar August 3, 2012

Q. Hello. I have a question about silver plated jewelry. Is .2 micron plating with e-coating sufficient as far as durability? I have been told that it passes a "72 hour salt spray test". If this will quickly rub off, what should be the thickness for silver plating and how can it be verified? Thanks!

Brenda Ross
- Los Angeles, California, USA
^


August 6, 2012

A. Hi, Brenda. It is the e-coating / clear coating that is passing the salt spray test, not the silver plating. And the silver won't quickly rub off because it is not exposed to the rubbing; it is underneath that clear coating.

But 0.2 micron plating is awfully thin (8 millionths of an inch). If you had a single ring with 1/16" thick silver plating on it, it would have as much silver as 7,800 rings with this thickness of plating.

I think that either I am misunderstanding you, or you are misunderstanding someone else, because it doesn't make much sense: It seems unlikely that someone would make rings and then focus their efforts on reducing the thickness of the silver so there was only 1/100 cent worth of silver on them instead of a 1/10 cent worth :-)

You asked how the thickness can be verified but you haven't told us who you are. If we start discussing a $35,000 instrument, and you are a manufacturer, that can make a lot of sense; but if you are a consumer buying a $5 ring, it wouldn't. What is your interest in the subject? Thanks!

Regards,

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


August 6, 2012

Q. Ted,
Thanks for your response and sorry to be so vague. The product I am referring to is silver plated jewelry, specifically necklaces and no rings. It is definitely plated with .2 microns. I am told that the factory specifies "normal thickness" as .02 microns and "extra thickness" as .2-.4 microns though I have no idea as to how durable this thickness is considered in jewelry that is valued at $18-$25 USD.

Thanks.

Brenda Ross [returning]
- Los Angeles, California
^


August 6, 2012

A. Hi again. Yes, I was misunderstanding you: necklaces are quite different from rings. I still think here is a typo or misunderstanding, as "normal thickness" surely must be 0.2 microns -- I'm pretty confident that .02 microns would not even be visible, and the jewelry would still be brass colored.

Again, I don't think the silver thickness will have any bearing on wear resistance, since it is covered by the e-coating. But there is a time-sensitive, temperature-sensitive, materials-sensitive phenomenon called "diffusion", whereby two materials slowly sort of melt together even at room temperature. If the necklace material is copper or brass, and there is no "barrier layer", like nickel, between the copper and silver, those two metals will slowly diffuse, but the thicker the silver, the longer it will be before it's a problem.

I don't think most people expect costume jewelry to last a lifetime like precious metal jewelry, so you may be able judge performance from a few pieces in circulation. A peek is worth a thousand finesses.

Regards,

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



To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)



Flash Gold Plating with Life of 3 months

July 22, 2010

Q. Hello,

Can anyone suggest the best way to plate the Copper and brass jewellery in economic way, and the plating should last for at least 3 months.

Currently the process we are doing is :-

Clean and buff the jewellery, then give copper cyanide flash 6-7 volt for 30-40 seconds, then again clean the jewellery in ultrasonic machine then after 4 plain water swills then 5% H2SO4 water swill, then again clean water swill; then load the jewellery in Acid Copper bath for 12 minutes at 3 volts - 30 amperes, then after that jewellery get good shine, then we clean the jewellery again in all earlier mentioned swills and then ultrasonic machine for 3 minutes.

Then we give flash of Yellow bronze at 3.5 volts for 15-20 seconds then, clean again with 2 swills and then again in ultrasonic machine. then finally we give gold flash of 5 grams of GPC (Gold potassium Cyanide) made of 5 ltrs Tank dissolve with 2 cubes of around 100 grams of cyanide and 1 drop of Silver potassium cyanide. We give flash 6-7 volts for 25-30 seconds then we give 2 swills of clear water then dip the drag out in Hot water of 85 °C. Then we dip drag out into anti-tarnish tank for 4 minutes then clean in 2 swills and again give dip into hot water and then keep in heater for drying the drag out.

The flash gold jewellery made through this process lasts only for 30-40 days.

We want to last our jewellery for at least 90 days.

Will appreciate if you suggest some other process with chemicals and lacquers that may be available in India which will help to last jewellery for 90 days.

regards

Rajan Parekh
Plating Shop - Mumbai, India
^


July 27, 2010

A. Hi,

You can go for an electrophoretic clear lacquering process and cure it at 130 °C, you may get a hardness for 4H and a thickness of 4-12 microns, so choose accordingly the thickness and hardness which will not effect your jewelry gold colour and brightness.

Regards praveen kumar
Praveen Kumar




plating process supplier
Mumbai, India

^


December 5, 2011

A. Why don't you try to plate with palladium after acid copper and then gold flash.

Artan Refeja
- Istanbul, Turkey
^

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