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Shelf life of Rhodium Plating Solution
February 16, 2012
Q. I am having problems with dark spots in the rhodium plating process. I recently called the manufacturer and was advised there is a 1 year shelf life to rhodium baths whether opened bottles or not. Is this a legitimate response? I bought a number of bottles a few years ago to "stock" up and a brand new bottle has given me terrible results.
My email to them,
I have been experiencing problems of spotting continually without remedy and am incredibly frustrated with the rhodium process. I use a Rectifier tuned to 5 volts and 2.5 amps. I have used a copper, gold, and stainless dip wire. I use a platinized titanium anode supplied by Stuller 2" x 3" approx. mesh. I use the Clean Earth electrocleaner and activator. I use reverse osmosis water in all but the plating solution. I have electrocleaned from 30-60 seconds @ 150 degrees F I have activate for 1 minute then plated in 110 F bath for 10-12 seconds. The result is a decent looking plate but upon closer inspection there is discolorization or spotting. Often the spotting is the worst close to the dipping wire. I just tried everything with a brand new bottle. I have purchased multiple bottles from you over the years and have been having unsatisfactory results. Unless something changes quickly I will be forced to find another supplier as the rhodium solution is the only thing I have not changed completely. I plate only rings of typically jewelry store size , solitaires, eng ring, men's rings, etc.
Jeweler - Canada
February 17, 2012
I think your current is too high. Try about 2 volts and leave the current to find it's own level. Increase time to between 30 seconds and one minute.
Red Sky Plating
Albuquerque, New Mexico
February 19, 2012
Its a shame that all your vendor came come with is that the Rh concentrate has expired. If I provided technical service of that level even years ago, I wouldn't have had many active accounts. I've had customers in the past use the same Rh plating solutions for more than four years. This of course is due to good plating practices and good housekeeping. I agree with Neil Bell that you should decrease your voltage. There is usually 8-12 grams of Rh metal per gallon in decorative applications, so you have to be very careful with voltage. Metal concentration goes hand in hand with applied amperage. You also want to be sure you have enough Sulfuric Acid in the bath. Good Luck!
process engineer - Malone, New York