Fasteners for the automotive industry must be protected from corrosion to ensure a long service life. Typically, pure zinc or zinc alloys are used as cathodic corrosion protection layers that can provide 720 hours or even more of neutral salt spray resistance, depending on the chosen system. In addition, zinc-nickel systems easily withstand the majority of cyclic corrosion tests and reduce the risk of galvanic corrosion.(…)
via Fastener Coatings and the Coefficient of Friction : Products Finishing.