What I was trying to point out is that some S2 zinc phosphate coatings my very well have been "colored" to be more black than zinc would normally be. Without coloring or other treatments manganese is going to be more black than zinc.
Black Oxide is more black than either ... but from what I have gathered it is beyond the capability of the average restorer to do "real" black oxide, which require some high temps and more exotic chemicals.
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