What the life depends on
The main factor is zinc thickness: thicker lasts longer because zinc is sacrificial—it corrodes in place of the steel.
Next come the chromate type/thickness and the environment—dry indoors is worlds apart from coastal salt air.
What salt spray tells you
The salt-spray test (ASTM B117) accelerates corrosion with a salt-fog chamber and records hours to white rust (zinc) and red rust (steel).
A figure like “72 h to red rust” is a lab comparison, not a number of years in service—but it compares quality between jobs well.
How to last longer
- Increase zinc thickness.
- Pick a darker chromate (yellow/green) over white-blue.
- Add a top coat/sealer for high salt-spray targets.
- For very harsh duty, consider a tougher coating system—ask our team.
FAQ
How many years will zinc last?+
No fixed number—it depends on thickness and environment; indoor parts last far longer than outdoor/salt-air ones.
Does 72 h salt spray equal X years?+
No direct conversion—it is an accelerated lab figure for comparing quality, not real service life.
Can you target a salt-spray rating?+
Yes—tell us the goal and we design zinc/chromate/sealer to pass, then verify by test.
Free Engineering Tools
- Hardness Converter HRC ↔ HV ↔ HB
- Which Steel Grades Harden — and How Far
- Fastener Weight: pcs ↔ kg
- Finishing Specification Builder for Purchasing and QC
- Salt Spray Test Plan Builder
- Coating thickness → thread fit (GO/NO-GO)
- Hydrogen Embrittlement — is baking required?
- Bolt Tightening Torque & Proof Load
- Thread Engagement Length
- Bolt Size Estimator (from load)
- Bolt Property Class — Mechanical Properties (ISO 898-1)
Related comparison guides
- Zinc plating vs Dacromet / zinc flakeZinc plating vs Dacromet: which coating for screws and bolts?
- Black oxide vs PhosphateBlack oxide vs phosphate: which finish for screws, nuts and bolts?
- Electroplated zinc vs Hot-dip galvanizingZinc plating vs hot-dip galvanizing: which one does your fastener need?
- Zinc plating vs Zinc-nickelZinc plating vs zinc-nickel: when is the upgrade worth paying for?
- Barrel plating vs Rack platingBarrel plating vs rack plating: how small fasteners are actually plated
- Zinc phosphate vs Manganese phosphateZinc phosphate vs manganese phosphate: match the coating to the job it does
Technical content review
Reviewed by the V.S. Heat Treatment QA and production team—heat-treatment and finishing operations since 1994 under an ISO 9001:2015 quality system.
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