Yellow zinc plating, also known as zinc chromate plating, is a popular corrosion-resistant finish for fasteners (bolts, screws, nuts, and threaded rods). It provides better protection than standard clear/blue zinc plating while maintaining a cost-effective solution.
Author: Marisa
Yellow zinc plating, also known as zinc chromate plating, is a popular corrosion-resistant finish for fasteners (bolts, screws, nuts, and threaded rods). It provides better protection than standard clear/blue zinc plating while maintaining a cost-effective solution.
A zinc electroplating process followed by a yellow chromate conversion coating.
The chromate layer enhances corrosion resistance and gives a golden-yellow iridescent appearance.
Contains hexavalent chromium (Cr⁶⁺) in traditional formulations, but RoHS-compliant trivalent chromium (Cr³⁺) is now widely used.
✔ Superior Corrosion Resistance
96–144 hours salt spray test (ASTM B117) vs. 48–72h for clear zinc.
Ideal for moderate outdoor exposure (automotive, construction).
✔ Good Adhesion & Lubricity
Helps prevent galling in threaded fasteners.
✔ Aesthetic Appeal
Yellow-gold finish is often used for military, automotive, and industrial applications.
✔ Cost-Effective Alternative
Cheaper than nickel or chrome plating but offers better protection than plain zinc.
❌ Not for Extreme Environments
Not as durable as hot-dip galvanizing or Dacromet in marine/coastal areas.
❌ Hexavalent Chromium (Cr⁶⁺) Restrictions
Banned in some regions (EU RoHS, REACH) unless exempted.
Trivalent chromate (Cr³⁺) is the eco-friendly alternative.
❌ Hydrogen Embrittlement Risk
High-strength fasteners (≥10.9 grade) require baking (200°C for 4–24h) to remove hydrogen.
Automotive (engine components, chassis bolts)
Aerospace (non-critical fasteners)
Military & Defense (meets MIL-DTL-3200)
General Machinery & Construction (outdoor exposure)
| Type | Corrosion Resistance | Appearance | RoHS Compliance |
|---|---|---|---|
| Clear/Blue Zinc | 48–72h salt spray | Shiny metallic | Yes (with trivalent) |
| Yellow Zinc | 96–144h salt spray | Golden-yellow | Only trivalent |
| Black Zinc | 48–72h salt spray | Matte black | Yes (with trivalent) |
| Trivalent Zinc | 72–120h salt spray | Blue/gold iridescent | Fully compliant |
ASTM B633 (Type II, Yellow Chromate)
ISO 4042 (Fastener Zinc Coatings)
MIL-DTL-3200 (US Military Spec)
RoHS/REACH (Trivalent Chromate Compliance)
If yellow zinc isn’t sufficient, consider:
Dacromet/Geomet (Zinc Flake Coating) – 500–1000h salt spray resistance.
Hot-Dip Galvanizing – Thicker coating, >200h salt spray.
Electroless Nickel Plating – Chemical resistance, 500h+ corrosion protection.
Yellow zinc (zinc chromate) plating is an excellent choice for fasteners needing enhanced corrosion resistance at a reasonable cost. It’s widely used in automotive, military, and industrial applications, but trivalent chromate is replacing hexavalent chromium due to environmental regulations.
For extreme environments (marine, chemical exposure), consider Dacromet or electroless nickel plating instead.