Zinc Flake Coating
Non-electrolytic zinc flake coating for fasteners per ISO 10683 — dip, spin and cure application, 240–1,000 hours neutral salt spray, no hydrogen embrittlement risk.
Last updated: 2026-11
Specifications
Zinc flake is the non-electrolytic alternative to plating: parts are dipped in a zinc-rich liquid, spun to remove excess, and heat-cured. Because no electric current and no hydrogen are involved, it carries no hydrogen-embrittlement risk — the deciding factor for high-strength bolts and spring steels that cannot be safely electroplated. It delivers corrosion resistance in the same class as zinc-nickel, takes lubricated topcoats for controlled torque-tension behavior, and is the standard finish where 240–1,000 hours of salt-spray life is required without plating.
| Process | Non-electrolytic: dip, spin-off, heat cure |
|---|---|
| Reference standard | ISO 10683:2018 (zinc flake coating systems) |
| Corrosion resistance | 240–1,000 hours neutral salt spray depending on system; example specification GMW3359 Code A at 720 hours |
| Appearance | Gray base coat; black or lubricated topcoats available |
| Lubrication | Lubricant topcoats achieve controlled friction — example COF 0.13 ±0.03 per ISO 16047 |
| Hydrogen embrittlement | None — non-electrolytic application, no post-plate bake required |
| Best suited for | High-strength bolts, spring steels, harsh-environment hardware |
Where this grade fits
Zinc flake is applied non-electrolytically, so it generates no plating-bath hydrogen and needs no post-coating bake — above roughly 1000 MPa tensile (about 32 HRC) it is often the only acceptable coating option, and it reaches 500–2,000+ salt-spray hours at 8–20 µm while keeping threads at nominal size. That combination is why the 12.9 and A490 pages point here.
Deep read: Hydrogen Embrittlement in High-Strength Bolts: Which Grades Need Controls, Which Coatings and Baking Schedules Are Acceptable, and What to Require Before the RFQ · Zinc-Flake vs Zinc-Nickel for High-Strength Fasteners: What the Evidence Settles on Hydrogen, Salt Spray, Friction and Specs
Materials
- High-strength carbon steel fasteners
- Spring steel washers and clips
- Alloy steel fasteners
Ordering & documentation
Documents
Shipments are backed by Mill Test Certificate (MTC), Dimensional Report, Salt Spray Test Report on request, with full batch traceability from raw material to finished product. Quality management follows the owner-confirmed compliance list: ISO 9001:2015, RoHS, REACH. Exact document sets are confirmed on the order.
Quotation
- The fastener family (Zinc Flake Coating) plus the standard designation from your drawing — DIN / ISO / JIS / ASTM / ANSI, or a drawing for custom parts.
- Size (diameter and length), thread type (metric or inch), property class or grade, and coating or finish.
- Quantity per size and your target delivery date.
- Destination country, and any required documents (for example a mill test certificate) so the quote includes them.
Sample & supply
Minimum order quantity is per batch, carried with the fastener order. Finishing run adds 5–10 days to the fastener lead time. Quantities or variants outside the standard range are confirmed at quotation.
Storage & shipping
Parts are packed for export and shipped factory-direct to buyers in Europe, Asia, the Americas and the Middle East. Store fasteners dry and protected until installation, and keep coated parts in their packaging until use; specific packing and preservation requirements can be stated on the order and confirmed at quotation.
Frequently asked questions
Why choose zinc flake instead of zinc-nickel plating?
The usual reason is hydrogen embrittlement: zinc flake is applied without electrolysis, so hardened high-strength parts carry no embrittlement risk and need no post-plate bake. Corrosion performance is comparable (240–1,000 hours neutral salt spray). Zinc-nickel retains advantages where conductivity, a specific black appearance or an OEM-mandated electroplate spec governs. Specify the finish the drawing calls out; both are delivered through the same coating lines.
What is the MOQ and lead time for this finish?
Finishing runs per batch carried with the fastener order and adds 5–10 days to the fastener lead time. Coated parts follow the finish line that processes them, so confirm the exact schedule against quantity and finish class at quotation.
What should an RFQ for this finish state?
State the base fastener (grade, diameter, length), the coating standard and class (for example ASTM B841 Class 2 with black trivalent passivate, or ISO 10683 with a specified topcoat), any thickness or salt-spray requirement, lubrication or torque-tension needs, and quantity per size — plus destination country and required documents such as a mill test certificate.
Related knowledge
- Reading a Fastener Coating Callout: ISO 10683 Designations, Salt-Spray Hours and What to Confirm With the Plater
- Zinc-Plated vs Hot-Dip Galvanized Fasteners: Which Coating for Which Environment
- Zinc-Flake Coating for Fasteners: When the Evidence Supports It, and What to Verify at the Coater
- Zinc-Flake vs Zinc-Nickel for High-Strength Fasteners: What the Evidence Settles on Hydrogen, Salt Spray, Friction and Specs
- Zinc-Flake Coating for Fasteners: When the Evidence Supports It, and What to Verify at the Coater
- Reading a Fastener Coating Callout: ISO 10683 Designations, Salt-Spray Hours and What to Confirm With the Plater
Request a Quote
Get factory-direct pricing from the manufacturer.
What to include in your inquiry
- ✓ Standard and property class (e.g. DIN 912, ISO 4762, class 8.8) — or a drawing for custom parts.
- ✓ Sizes, lengths and thread type (metric or inch).
- ✓ Quantity per size and your target delivery date.
- ✓ Destination country, plus any coating or finish requirement.
- ✓ Any documents you need with the shipment (e.g. mill test certificate) so the quote includes them.
- ✓ Your inquiry goes straight to the factory team by email and gets a reply within 24 hours.
- ✓ Factory-direct pricing
- ✓ Standard and custom specifications
- ✓ Factory-direct export to buyers in Europe, Asia, the Americas and the Middle East
- ✓ Full fastener family support