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Lacquer for gold plating

Some clearcoating solutions (adv.) pointer   



A discussion started in 2004 and continuing through 2017 . . .

(2004)

Q. Respected sir,

I start gold (flash) plating plant on imitation jewelry in January-2004. My quality of plating is best in my city. I do gold plating on copper plating then lacquer plating. I use P.U. lacquer on gold plating.

My customer is satisfied with my work but I'm not. I want more hardness on my job. can you help me?

And one more thing I want to ask u-what is the chemical formula of P.U. lacquer? I wish you reply as quickly as possible.

Thanking you, yours faithfully

Kishan Patel
ele. mfgr. - Rajkot , GUJARAT, India


(2004)

A. You can use any proprietary epoxide base lacquer.

Goran Budija
- Zagreb , Croatia


(2004)

A. You can also use thin, very hard coatings based on "siloxane" chemistry (usually heat-cured). They give a glass-like hardness and are resistant to almost all chemicals except caustics. Most would need a primer on gold.

Polyurethane (P.U.) lacquers can be relatively soft or somewhat hard, depending on how they are formulated. The hardest ones are always two-part coatings, or UV-cured. Usually they would be much thicker than a siloxane coating. A polyurethane is a chemical reaction product of an isocyanate compound (usually a di-isocyanate) and one or more glycols.

Dr. William Lewis
- Chula Vista, California


(2004)

A. Dear Mr. Kishan Patel,

In the plating field there are terms used for the hardness.There are two terms used as specifications for the kind of coating you are doing.

We call them as

1. Perspiration cycles which are indicative of the resistance to the human perspiration.
2.Abrasion resistance which are accelerated tests with some chemicals.

Please decide the quality of the coating you require. There are materials available with different quality in respect of terms I mentioned.

Best Regards

Suhas S. Mahajan
Paint technologist - Pune, Maharashtra, India


(2006)

Q. Sir,
We are manufacturing original 22 kt gold plated (1 gram) chains. The shining & brightness of the chains are very good in our area. We are planned to go for lacquer coating for improve his reliability. When using lacquer coating (Electrophoretic Coatings, Polyurethane Based, Make: Atotech, Electro Clear 2000) the shining & brightness of the gold plated chains are dim compared to non lacquer coated chains. How can I improve its brightness? Any process is there, before lacquer coating. Can you help me?

I wish you reply as quickly as possible.

Thanking you,

Your faithfully

M.K. Mohamed Raja
gold covering - Chidambaram, Tamilnadu, India


November 7, 2010

Q. How I can use lacquer on imitation jewelry, epoxide base lacquer and "siloxane" chemistry on jewelry articles?

abhishek agrawal
- khirkiya M.P. india



Lacquer isn't tough enough? How about E-Coat, Trivalent Chromate, or PVD?

November 26, 2014

Q. I work for a jewelry company that makes modular pieces out of smaller scale brass tubes --

30273-1a  30273-1b  30273-1c

We currently plate our brass tubes with a true 14k Gold or Imitation Rhodium (White Silver) or Gunmetal/Hematite finish, then they are lacquered. We are having issues with durability and with the lacquer chipping or peeling off. Additionally, we are considering a handbag line and are afraid that the lacquer will not hold up to the wear and tear of daily use.

We looked into PVD Coating and found that 1) the PVD didn't adhere well to brass, meaning we would then have to try to chrome coat the brass before PVD coating or 2) switch the tubes to Stainless steel (worried about nickel content and international testing regulations) or Titanium (not a readily available/affordable option). Also, we came across racking issue (since these are smaller pieces) and the overall price of the PVD coating was well beyond our cost limitations.

We then tried sourcing a company that could do in-house plating and decorative clear E-Coat. Most companies that do offer e-coat seem to be geared towards industrial manufacturing and only offer a black color.

Chromate coating was recommended, but my internet research is finding that Trivalent Chromate is primarily for corrosion resistance.

I was wondering if anyone could provide additional information on Trivalent Chromate Coating over plated brass or if there were other suggestions to achieve the look we currently have while being tougher than our current lacquer process.

Spivey Jean
Operations Manager for Jewelry Designer - Brooklyn, New York, USA


November 2014

A. Hello Jean. Chromate is an easily abraded coating and not necessarily decorative; I don't think it's what you are looking for.

If PVD is not the right answer for you, I think electrophoretic lacquer is. Although e-coating is used as a primer in the automotive and other industries, and "most" shops may apply it for that purpose, clear or tinted e-coat lacquers can be used as a decorative topcoat.

You might also try automotive 2-component clearcoat, or UV-hardened clearcoats. Of these, the e-coats are probably the thinnest.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


December 3, 2014

A. Not sure who did your PVD for you, but I've not had a problem PVD coating directly onto brass. The general reason it is not done is that the PVD coating does not prevent the brass from tarnishing, so over time the finish changes. Hence, it is common to plate the brass with nickel and a thin chrome layer before PVD (though the chrome layer is not really necessary). The nickel provides the corrosion resistance and provides a harder base for the very hard PVD coating. Of course, now you have the nickel allergy issue -- not to mention the cost -- but you will have substantially better wear resistance than you will with any other coating.

treglio portrait
Jim Treglio
- Vista, California



October 10, 2015

Q. Hi sir, I have an imitation jewellery business in Delhi. I sell daily-use gold plated jewellery in our city. How can I guarantee this jewellery at least for 3-4 years. Please tell the procedure to do this.

sandeep chadha
- new delhi, moti nagar, india


October 2015

A. Hi Sandeep. 3-4 years is a lot to ask of imitation jewelry, especially if it is a medium to high wear item as opposed to a periodically worn and almost never touched brooch. This thread suggests as possibilities: epoxide base lacquer, siloxanes, polyurethane based electrophoretic coatings, UV-hardenable clear coating, automotive 2-component clearcoat, heavy gold plating, or PVD coatings.

Heavy gold plating is probably not the answer you'd like for imitation gold jewelry because of the high cost of the gold. PVD may not be the answer if you need to do it yourself or in low volume.

Of the remaining 5 possibilities, do you have any experience with any of them, or any questions about any of them? Must your jewelry be nickel-free? This is just one of more than a dozen threads here on essentially the same subject, and it probably isn't especially productive to essentially re-ask a question which has been asked and answered dozens of times unless you can enunciate how the specifics of your situation differ from the previous questions, so as to make some of the 7 proposed solutions less attractive. Can you describe your pieces' shape and use, their base material, your price point, and your daily volume? Best of luck!

Regards,

pic of Ted Mooney
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



May 15, 2016

Q. Hi sir,
Sorry for late replying.I have no experience about any kind of lacquer coating and my jewellery is copper based and gold plating. We use two kinds of plating: first one is nickel-free copper gold plating, and second one is micro gold plating for high range quality. We sell all kinds of jewellery for all kinds of customers but for lacquer coating we go to someone else; we need to start our own lacquer coating plant for jewellery please. Suggest me what is chemical formula of pu lacquer.

Thanking you

sandeep chadha [returning]
- India,delhi,moti nagar


May 2016

A. Hi. Sorry, I would have no idea how to formulate polyurethane coatings from basic chemicals. But just because you wish to apply the coatings yourself doesn't mean you also have to become a plastics formulator; surely there are many suppliers of such coatings you can purchase from, with several references earlier on in the thread.

Still, returning to the original premise, I doubt that a 2-part polyurethane coating can be guaranteed for 3-4 years, but good luck.

Regards,

pic of Ted Mooney
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



Lacquer for silver castings

June 12, 2016

Q. Hi sir. I am Karthick from Chennai. Ii have started a new casting unit. I should know about the difference between e-coating and lacquer coating. Please give me an idea. I need the chemical, where would I get the chemical? And one more question, can I can use the lacquer for silver rings? Thank you sir I am waiting for your reply.

B karthick kumar
- Chennai Tamil nadu india


June 2016

A. Hi Karthick. As you can see, this thread has been running for 12 years now, and sometimes it takes a very long time for anyone to improve the answers. Hopefully you'll get a good answer, but please don't wait for it :-)

Lacquer probably refers to a nitrocellulose or another coating which dries, i.e., the solvent evaporates, leaving the solids behind as a lacquer coating. But "drying" is not the only way a clear liquid coating material can be converted to a solid. They can cure as reactions between two components, as in epoxy coating or two-component automotive clearcoats; they can be radiation (UV) cured like women's fingernail lacquers applied by manicure shops; or electricity can convert molecules of polyurethane or other plastic to a solid while the parts are immersed in a solution, as in cathodic electrocoating.

Yes, these coatings can be applied to silver as well as to gold, but things gets a bit confused when we mix silver castings into this discussion because the reason for clearcoating thin gold plating (preventing wear) is rather different than the reason for clearcoating sterling silver objects (preventing tarnish); plus, while lacquering or clearcoating of some sort may be the best idea for gold, rhodium plating might be a better idea for the silver.

Regards,

pic of Ted Mooney
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey



June 18, 2016

Q. Hi, I am Ibrahim from Calicut. I have started electroplating plant. My jewellery is copper coated and gold plated and lacquer coated. Now I use the lacquer, but it is not better (PPG asian). Which lacquer is long time, means giving 2 or 3 years guarantee. Please give the information.

mohd ibrahim tk
imitation jewellery - calicut, kerala, india

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Ed. note: We don't compare brands on this site, but if anyone has technical advise on a different type of lacquer, or a different protective coating, or other aspects of the question, that would be great.




Lacquer which will long last more than 2 years

30273-2
November 15, 2016

Q. Hello, I'm Vaibhav from Bangalore, I want to know the best lacquer which will last more than 2 to 3 years on daily used product like mobile phone; does gold plating colour long last depend upon thickness or quality of lacquer, please suggest me a good lacquer which will last long.

THANK You.

Vaibhav Gowda
Student - India

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Ed. note: Letter 56727, "Gold Plating Iphones and mobile phones, Q & A's", addresses very similar issues.




Clear coating of Cu/Ni/Sb/Au/Black Zinc plating on zinc die-casting for Anti-scratch application

February 15, 2017

Q. I work in jewelry accessories now, and have a headache on scratch issue for some specific application these days.
To avoid too much cost, we look for "Clear coating of Cu/Ni/Sb/Au/Black Zinc plating on zinc die-casting for Anti-scratch application" -- hope anyone can give us an idea, thanks

Charles Lin
- Taiwan
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