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Silver or EN plating on Tellurium Copper

Quickstart:
     Plating onto tellurium copper is different than plating into other grades of copper.
     Per two respondents you should start with an acid plating process, not a cyanide plating process, and hot entry is advisable. Another respondent reports success starting with a nickel or copper pyrophosphate strike.
     Per a fourth respondent, a cyanide silver strike might be okay but only with a copper etch first.
     Read on, join in ...

(this entry appended to this thread by editor in lieu of spawning a duplicative thread)
Q. My name is Sunil, and I run an electroplating business in the city of Jamnagar, India. I need to perform silver plating on tellurium copper. The problem I am encountering during the trials is that the plating turns black in areas where the current density is low.

Sunil Mamtora
Shop - Jamnagar (Gujarat)
March 26, 2026

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⇩ Similar, related, Q&As -- oldest first ⇩

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Q. I have spent hours reading through many of your questions and responses, which has given me a wealth of information regarding the plating process. This site is what the Internet is all about and I would like to compliment you on its creation and maintenance. We designers can never know enough about all of the different materials and processes that we encounter and it is wonderful to have sites like yours to help further our education. Thanks very much.

We have designed a fitting that is to be produced in C14500 tellurium copper, because of its lead-free composition and good machinability -- scheduled for bright silver plating as the final surface finish. I have the general impression that some of the free-machining alloys can create problems with the plating process and as a preventative measure, I am researching this issue to try to give our plating contractor as much information as possible and to try to anticipate and avoid any potential problems. He is not familiar with this particular alloy and I was wondering if anyone has had any experience with it or recommendations that they would care to impart.

Again, many thanks to finishing.com and to all those who have taken the time to respond to inquiries such as this.

Sincerely,

Jim Baxter
industrial design - Fort Lauderdale, Florida
1998

Ed. note: Thanks for the kind words, Jim. We provide the space but our wonderful and generous readers provide the value  🙂

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Preventing tarnishing of Tellurium Copper

Q. I have the opportunity to machine a component for one of my customers made of Tellurium Copper 145. Tarnishing of this part is a concern. This component is part of a fiber optic surgical assembly. Is there a process to prevent Tarnishing of Tellurium Copper 145?

Jeff E [surname deleted for privacy by Editor]
- Hamel, Minnesota, USA
2002

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Electroless Nickel + Silver Plating on Tellurium Copper

Q. We have to plate TeCu with electroless nickel 100 micro inches, sliver over that 200 -300 microinches , any suggestions on the pre treatment? We are finding black dots inside the component & white patches on the outer surface, any suggestions? ⇦ Answer?

Chethan
- Bangalore, India
2005

Q. We want to call out an electroless nickel plating on a C14500 tellurium copper part. We would like to use electroless nickel because of its uniform coverage of irregular shapes, internal surfaces and edges. Its hardness is also a plus. The environment is not corrosive.
Questions:
1) What is the practical minimum thickness range that can be specified?
2) At that minimum thickness range, does heat treatment provide any increased hardness benefit?
3) What callout can we put on the drawing that will be understood by most shops? What do the various classes and types mean? (It looks like the MIL spec is obsolete. Is ASTM the way to go?)
4) Can electroless nickel be used in the United States where there is incidental food contact?

Thanks very much for any help. We have not previously used electroless nickel.

2005
John Bussan
manufacturer - Chicago, Illinois, USA

Q. Hello:

We have some parts that are manufactured out of 6061 AL, with integral Tellurium Copper inserts. Imagine a .5x6x6" piece of AL, with a 2x2" center section made of the Te-Cu, with a seamless transition from the AL to the Cu (no gaps). The customer wants to electroless nickel plate the entire part. My concern is the different pre-process requirements for Al vs. the copper. Can this be done? Anyone have any experience with EN plating of a two-metal part like this? Many thanks in advance for any help!
Joe Osborn
Manufacturer - Novato, California
April 17, 2014

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Cleaning/pretreatment of tellurium copper

Q. We recently switched from pure copper to tellurium copper in some of our products. Since we drill a number of small cross holes in the part, we use a thermal deburr to remove the burrs. The copper was fairly easy to clean and make shiny. The tellurium has proved to be a challenge to get anywhere near the same finish. Any suggestions.

Robert Wakeman
- Watertown, SD, USA
2007

Q. We have adhesion strength problems on Tellurium Copper parts after Silver Plating.
Of course, the parts are Pre silver plated. Brass Parts on the same rack are okay, the Tellurium Copper parts show blistering.
Which would be the correct Pretreatment before silver plating or pre silver plating?

Thanks a lot.

Wolf Werner
- Mexico City , MEXICO
2007

Q. Silver plating on tellurium copper:
After silver plating, plating is get peeling after 20-40 hours.

Ramsing S Rajput
mss - nashik, Maharastra, India.
July 15, 2015

? Hi Ramsing, Dominick and James requested briefing on the cleaning and etching steps in order to help further. Are you doing the copper sulphate strike that Robert suggested? Are you doing the nickel strike or the pyrophosphate copper that Dan suggested? Are you simply cyanide silver plating the tellurium copper? Please try to understand that those four helpful and very knowledgable platers are unlikely to even acknowledge your posting since you haven't acknowledged theirs. Please help us continue to move forward by providing some process sequence info  🙂 Thanks & Regards, Ted Mooney, P.E. RET Striving to live Aloha finishing.com - Pine Beach, New Jersey Need quick confidential answers? $25 Need project assistance? $100/hr.

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Multiple threads merged: please forgive chronology errors and repetition  🙂

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Q. Hi there,
I have recently set up a new silver plating plant, plating copper and brass parts to be used as electrical connectors. The reason for plating these parts is for corrosion protection as these connectors are used in highly corrosive environments such as mines and on railways. My plant has been operational for roughly 3 months and I have as much plating experience.

My plating line is as follows:
1. Alkaline Soak/Electroclean,
2. Rinse,
3. Acid dip.
4. Rinse,
5. Copper Strike (cyanide),
6. Rinse,
7. Silver Strike (cyanide),
8. Silver Plate (cyanide),
9. Rinse,
10. Rinse

I get the parts directly from machining. The silver deposits on the brass components are bright, and adhere very well. However, when plating copper components (C147 -- Sulfur bearing copper) there are several problems.
The end result is the copper plated parts are poor, there are a couple of things wrong:
Firstly some of the surfaces have frosting, mainly the machined surfaces, the non-machined surfaces are bright silver.
Secondly, the plating de-laminates (peels-off) when tested, seemingly only the silver strike and silver plating peels off, not the copper strike.

These problems confuse me ... I would expect the machined surfaces to be bright silver given their clean finish; and the plating peeling off most likely means bad cleaning, but if that was the case you would expect the copper layer to peel off also.

A few observations:
- Brass parts come out perfectly, so the problem is only with copper, we use copper 147 for easy machining. I have heard from another plater that C147 oxidises in contact with cyanide however I have not been able to find another source supporting this.
- The machined areas on the parts get a black frosting look during the silver strike, my guess is that this is part of the reason the frosting occurs in the silver plating bath. (The parts have no such phenomenon after the copper strike)

Things I have tried to rectify the problem
- In the first process tank I have tried: Cathodic cleaning with an anodic flash, anodic cleaning, and no electroclean only soak.
- A longer copper strike
- Higher and lower voltages in the silver strike
- Higher and lower voltages in the silver plating bath.

I would like some direction as to why the copper parts turn out so poorly, and what can be done about it.

I have attached some photos to make understanding my problem easier.

        

Thank you for taking time to read my question, and for any advice you may have.

Juan Kritzinger
- Newcastle, NSW, Australia
January 9, 2023

A. I do not know "C-147", but if it contains Tellurium, then you must strike in an acid solution (even acid copper) first. Cyanide will not plate onto bare Tellurium copper. Robert H Probert Robert H Probert Technical Services Garner, North Carolina A. In my experience you cannot treat the brass parts the same as the copper. You do not need a copper strike step for your copper parts. My shop Utilizes a persulphate etch step in the plating of copper substrates. A example procedure is as follows: 1. Soak/Eclean and rinse 2. Acid dip and rinse 3. Copper etch and rinse 4. Acid dip and thorough rinse 5. Silver strike into silver plate etc You could try just removing the copper strike step to see what the adhesion is like, but all of our procedures utilize a copper etch before plating. E Gonzales - Boulder Colorado January 10, 2023

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