What is "Valve Pitting"

[HuffPuffTuba]

So, when I was browsing TubeNet, I sometimes saw people talking about "valve pitting". What is "valve pitting"?

[Dan Schultz]

I recently used that term on my 'for sale' page to describe the pistons in a tuba I had here. There may be a more scientific explanation for what I said is 'minor pitting' but for lack of better words.... the surface of the pistons resembled a very shallow effect that's called 'orange peel' when used to describe paint.

It looked like the pistons had a some point suffered some minor corrosion and nickel had been applied in an effort to restore their size.