Fastener Coatings Compared: Zinc, Zinc-Nickel and Passivated Stainless
Corrosion protection is a coating decision made long before the first raindrop. The three mainstream choices trade cost, protection and process risk.
Electroplated zinc: the budget baseline
Zinc sacrificially protects steel and takes color passivates (blue, yellow, black) cheaply. Unsealed blue zinc survives ~96–200 h of neutral salt spray; sealed systems push higher. Watch hydrogen embrittlement on hardened parts — baking after plating is not optional above 1000 MPa.
Zinc-nickel: the automotive workhorse
Alloys with 12–15% nickel deliver 480–720 h salt spray unsealed, better galvanic compatibility with aluminum, and stable friction coefficients — which torque-controlled lines love. It is the default spec for EV and chassis hardware exposed to road salt.
Stainless with proper passivation
For permanent exposure or wash-down, A2/A4 stainless passivated per ISO 3506 sidesteps coating life questions entirely — at material cost and with galling precautions.
Decide with the mission profile
Match coating to exposure hours, then verify friction data for your torque spec. Topprecision plates in-house partners supply full salt-spray reports per lot, and we publish K-factor ranges per finish so your torque windows survive the coating change.
