· 3 min read · by KVEE METALS
Trivalent vs Hexavalent Passivation: RoHS and ELV Compliance for Automotive Exports
Hexavalent chromium is restricted under RoHS and the EU End-of-Life Vehicle directive. Trivalent (Cr3+) passivation delivers a compliant zinc plated finish without sacrificing corrosion protection.
If your components end up in vehicles or electrical equipment sold in Europe, or in supply chains that follow those rules, the passivation on your zinc plated parts matters as much as the zinc itself. This guide explains what the regulations restrict, how trivalent passivation works and what to check when converting an existing specification.
Why hexavalent chromium is restricted
Traditional yellow and blue chromates contain hexavalent chromium (Cr6+), a compound classified as carcinogenic. Two European regulations drive most of the requirements Indian component makers see:
- RoHS (Restriction of Hazardous Substances) limits hexavalent chromium in electrical and electronic equipment to 0.1% by weight in homogeneous materials.
- ELV (End-of-Life Vehicles directive) restricts hexavalent chromium in vehicle components, with only narrow exemptions remaining.
OEMs and Tier 1 suppliers push these requirements down the chain through material declarations and IMDS entries, so a fastener plated in Nashik is expected to comply even if the vehicle is assembled elsewhere.
How trivalent passivation works
Trivalent (Cr3+) passivation forms a conversion film over the zinc using trivalent chromium chemistry, with no hexavalent chromium in the bath or in the finished film. Modern formulations, often paired with a sealer or top coat, match or exceed the corrosion performance of the hexavalent films they replace.
- Trivalent blue: a clear-blue thin film, the direct replacement for hexavalent blue. Typical salt spray guidance is 48 to 96 hours to white rust.
- Trivalent yellow / thick film: a thicker Cr3+ film, sometimes dyed or sealed to give a yellow appearance, with 120 to 200+ hours to white rust when sealed.
- Trivalent blue + lacquer: a clear lacquer over trivalent blue for 200+ hours and a glossy finish on visible parts.
Performance differences to know
| Property | Hexavalent chromate | Trivalent passivation |
|---|---|---|
| Hexavalent chromium content | Present | None |
| Self-healing of scratches | Yes (mobile Cr6+) | Limited; sealer compensates |
| Heat stability | Degrades above ~60-70 °C | Stable through baking |
| Colour consistency | Strongly iridescent | Less iridescent, more uniform |
| RoHS / ELV compliance | No | Yes |
The heat stability point is important for high-tensile fasteners that need de-embrittlement baking after plating: a trivalent film keeps its corrosion performance through the bake, while a hexavalent chromate loses much of it.
Converting an existing drawing
- Identify the current call-out. "Zinc yellow" or "Fe/Zn 8 C" style notes usually mean hexavalent chromate.
- Agree the target performance, typically the same hours to white rust and red rust in salt spray.
- Select the trivalent system. Blue for interior parts, thick-film or sealed variants for underbody and outdoor hardware.
- Run a trial lot and test it. We can supply samples for your salt spray or third-party lab.
- Update the drawing and material declaration so the new finish is traceable.
What we offer
KVEE METALS runs trivalent blue, trivalent yellow and trivalent blue with lacquer alongside conventional zinc finishes, so a customer can move a programme to a compliant finish without changing plater. Share your drawing and we will propose the equivalent trivalent specification.
Need this finish on your components?
Send a drawing or sample and we will confirm process, thickness and pricing.
