Black Zinc Finish
Black Zinc Coating, also known as Black Oxide, has the same properties as Bright Zinc Plating (BZP), just in a black colour rather than the common silver or yellow.
A Zinc coating does contain some outdoors properties. This means that it can be used in outdoor environments for a limited time. This coating will show signs over rust over time.
The black colouring is more of a dark grey finish and will show signs of wear quite quickly. This has a rustic or industrial feel to the finish. This is displayed more evidently on on large nuts and washers.