Rhodium Pen Plating Problems

A. Dear Mr. Dipen,

1. electroclean your job or ultrasonic and see there should be no water breaks
2. water rinse
3. water rinse
4. 5% sulfuric acid dip
5. water rinse (all water rinses should be of d.m water)
6. pen rhodium (keep voltage 5-6 volts , soak your tip of pen 1 hour before plating , roll around the tip gently and don't apply pressure on tip during operation and try to keep tip always wet)
7. water rinse
8. water rinse
9. dry

Hope this tips will do well.

A. I think you should control that the voltage you put in your pen plating machine is real.
For example there are a lot of machine that you put on 3 V but if you rally control tension you can test 1 or 2 or 5 V.

Bye Giacomo

A. Hi Joshua,
Sounds like you have severe burning. Soak the pen plating tip in the solution for at least 15 minutes before plating. Move quickly on the part, staying in one place too long can cause burning. Keep the tip wet. I would start with a fresh rhodium pen plating concentrate to rule out any solution problems you may have. If the Rhodium metal concentration is too low, burning will occur. The voltage is usually predetermined by your supplier, check to make sure it's correct. Good luck!

A. Hi Joshua,
Please ref. discussion below in this topic. Your problem and suggestions/remedies are identical.
Further keep two brushes -- one always keep dipped in DM water to wet/clean the surface to be plated and the other to plate. Adjust the distance between cathode and anode by trial and error method to suit your need. Apply brush one way and not reverse.
Regards

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A. First of all, tell us what you are doing. Secondly, rhodium is not an alloy but a pure metal. Thirdly, have you tried a Hull Cell panel test and if so, does it come out as you want it to?

A. You had mentioned you had a rhodium plating bath. Are you using the bath plating solution for the pen plate application? If so, what is the Rh metal concentration in the bath? Because you are experiencing a greyish color that tells me the rhodium and / or sulfuric acid concentration is too low for pen plating. What voltage are you using? That may be too high. I would contact your rhodium supplier and have them sell you a pen plate concentrate (ready to use), and have them fax you a data sheet with clear instructions. Some suppliers will add a little phosphoric acid to make the finish somewhat whiter. Good luck!

A. Dear Christos
The chemistry of bath plating Rh and Pen plating Rh is entirely different. Generally bath Rh conc. is 2 grms/ltr and pen plating sol'n has high (many fold) conc. of Rh.
Voltage used is higher than the plating voltage.
Variation of distance between the anode (in this case the clip) and the cathode (the pen),the voltage applied, the conc. of metal -- all play important roles. The expertise of applying the pen (brush) is also important.
Please explain the procedure you follow (with details), and maybe I can explain better.
Regards,

A. Hi Lalit. Etching reduces the weight of jewelry and plating increases it, but ...
Any etching of a precious metal is going to be minimal, and with rhodium costing up to $12,000 per ounce several times in the last decade or so, you can be confident that the weight applied is incidental. Thicknesses are often in the 0.1 micron range; you are welcome to do a weight increase calculation based on this, but I think you'll find that my dismissing it as 'incidental' is justified.

Luck & Regards,

A. Hi Ravichandran. The basic ingredients are about 2 grams per liter rhodium sulphate plus sulfuric acid -- but please contact a plating process distributor in Bangalore and they will offer you the proprietary solutions from Degussa, Technic, Cohler, Davis-K or others. Usually there will be a starter solution and a maintenance solution. Pen plating solutions are sometimes more concentrated and sometimes contain thickening agents, perhaps fumed silica or barium sulphate -- I don't know.

This is not something that you usually make yourself; first, because a lot of development effort may be required; second because you need to work with a knowledgable and well equipped lab to troubleshoot the inevitable problems and unless you have that exotic equipment yourself you'll need them to use theirs; and third because rhodium is so terribly expensive that you can't waste any in trial and error. Get back to us if you have further questions.

We have 60,000 threads on line here on 60,000 topics, so please post your questions about cleaning formulations on a more applicable thread. If the threads wander too far, no one will be able to find anything :-) Good luck.

Regards,

A. Brightener for rhodium plating is available in the market. You can contact some of the companies in Kolkata.