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Rh plating on internal Pt-coated surface

I have a ceramic piece with a complex internal structure, similar to a monolith. It has a continuous Pt coating that covers half of the internal surface and extends to a contact point on the external surface. We would like to plate Rh onto part of the Pt surface. We can bring the part of the Pt we want to plate into contact with the plating solution by partially filling the piece with the Rh plating solution. The monolith channels are rather narrow, only about 1 mm wide, and are more than 8 inches long. We can complete the circuit through the Pt contact (the Pt stripe is about 5 microns thick and 10 mm wide).

How would you suggest we conduct the plating? What Rh plating solution, current density, etc? (We would prefer not to use cyanide or solutions with pH less than 2 due to the delicate nature of the ceramic piece.)

T. Joseph Mazanec
Chemical industry - Solon, Ohio, USA
2006

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The phosphoric acid bath is less corrosive than the sulfuric one but I don't know that you can get above pH 2 and still kept the rhodium in solution. Current density between 10 and 50 amps/sq ft. How are you going to get an anode into a 1mm wide space?

Neil Bell
Red Sky Plating

Albuquerque, New Mexico

2006