breaking down nickel plated brass

I will probably ask in the correct forum "Does it matter if the Brass is Chrome or Nickle plated? And why does it not seem to matter?". One day......
Sort of a 'Whats OK as a 'crossover' metal, in metals?'

Like, I know its OK to have Copper in your Brass, as Brass is a mixture of Copper and Zinc, so all it means is that on average I have only upped the percentage of Copper in my Brass.



Same with Magnesium in my ' Aluminium domestic'.
And
Silver in my 'Copper domestic'

i was just curious because of the price difference between clean and dirty brass. i wanted to know if it was worth breaking them down as far as possible. if you have to take out the springs inside and such. thanks for your responses