How to produce black Ni-PTFE finishing?

Need help on composite electroless Ni-PTFE plating on stainless steel, followed by a blackening chemical immersion. Always get uneven finishing when done in lab scale plating, i.e. beaker [beakers on eBay or Amazon [affil link] with magnetic stirrer. Do I need special agitation for the plating?

For the post-treatment, have tried using Nitric Acid(20% to 50%); or mixture of ammonium peroxidisulphate, sodium disulphate, iron(III) sulphate & ammonium thiocyanate ⇦ on eBay or Amazon [affil link] , but both have adhesion problem or only brown finishing.

LF, Loh
- Singapore
2001

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