Have a question on parkerizing and how much material is removed from the item

[sar32]

I have this gas block off my AR 556 that I had parkerized gray but now I want it to be black so every time something is parkerized do they sandblast it and how much material comes off the block itself .The gas block is steel. Im mainly concerned about the inside of the block where it slides down onto the barrel about material being removed.

[l921428x]

They can and do use different types of media to "sandblast" steel shot, sand and glass bead.
it is like grades of sandpaper. I shouldn't worry to much. And I do know how they take the park
off. Let us know.....