Factors to weigh
The right finish cuts cost and extends life. Weigh five main factors:
- Environment — indoor, outdoor, humidity, salt, chemicals.
- Hardness/load — do you need the metal itself hard?
- Appearance — what color, glossy or matte.
- Tolerance — fine threads that can’t take a thick coating.
- Budget and volume — high counts need controlled cost per piece.
Match the job to the process
- Corrosion + color, good value → Cr3+ zinc plating (color from passivation).
- Looks, black, preserved thread size → black oxide (+ rust-preventive oil).
- Paint primer / reduced friction → phosphate coating.
- Hardness / clamp load → heat treatment before surface finishing.
- Very high corrosion / marine → stainless or a heavy-duty coating system.
Combining processes
Real jobs often chain steps: harden the bolt first, then Cr3+ zinc-plate for corrosion, then bake out hydrogen on high-hardness parts. The right sequence matters for quality.
V.S. Heat Treatment does it all in one place — hardening, zinc plating, phosphating and testing — so quality is controlled end to end.
FAQ
Harden first or plate first?+
Harden first (set the metal’s properties), then zinc-plate the surface, then bake out hydrogen on high-hardness work.
Not sure what to choose?+
Send a sample or usage spec and our team will recommend a process to fit your budget and real use.
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.
View evidence and report format
