[Amps] Copper Pi tank coil oxidisation

[Mark Marsden]

Hi

I'm in the commissioning and measurement stages of my homebrew 
4CX1000A amp project (1600W out now and looking good).

A couple of weeks have passed by since I wound the Pi tank coils
using 5mm Cu tubing. Since then the copper has gone from shiny
to dull brown by oxidation.

Does this matter very much? I guess the RF skin resistance won't 
be affected very much to affect HF efficiency.

Are there any recommendations for coating Cu tube to keep it 
shiny and is it worth it (for more than cosmetic value)? 

73 Mark G4AXX