I think it's just Silver plating onto the stainless steel of the needle. If the Silver deposit in the needle is reducing the flow then I would suggest soaking the needle in a silver solvent such as Sodium or Ammonium Thiosulfate (Fixer).
There are adapters made that are female luer-lok to tubing and tubing to male luer-lok. The male luer-lok connection is where you attach the needle and place in the kettle. These may be available from the Vet supply Co. Chris mentioned earlier or eBay..
All the best,