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Surface prep. for 446 S.S. prior to platinum plating

We currently platinum electroplate 446 stainless steel using an ammoniacal process. Prior to plating, the parts are degreased and washed using ultrasonic cleaners, then the surface to be plated is grit blasted and triple rinsed with DI water. We have attempted to moved to an acid etching (mixture of nitric, phosphoric and hydrofluoric acids) step prior to plating for better process control, but are now having with adhesion of the plating. Can anyone suggest a chemical process for preparing the surface prior to plating that won't cause difficulties with adhesion?

Andrew Dummer
R&D Physicist - RTP, North Carolina
2003

Try a Woods Nickel strike before plating. It is a simple plating bath to make. If you can't have a thin layer of nickel plating under the platinum I have had good success and adhesion plating 400 SS alloys by blasting, 5 min. alkaline anodic electroclean , 5 min. muriatic acid pickle 1 min. alkaline anodic electro clean and then plate.

Todd Osmolski
- Charlotte, North Carolina, USA
2003