The finish is zinc parkerize.
Phosphate is a porous crystalline coating of zinc or manganese phosphate produced on ferrous metal surfaces.
Zinc Phosphate:
# Excellent for holding oil and adhering to paint
# Improves lubricity
# Gray in appearance
Manganese Phosphate:
# For prevention of metal-to-metal contact
# Wear Reduction
# Coat is a base for dry film lubricants
# Black in appearance
In other words... You can park and leave it or paint over it. in ANY color you want.