Yellow vs. Blue vs. Black Zinc Passivation: Color Guide
Zinc plating color is more than just aesthetics. Learn how the different trivalent passivations differ in salt spray performance and corrosion resistance.
When you order “Zinc Plating,” the next question from the plater will be: “What color?”
The color of a zinc-plated part comes from the passivation layer applied immediately after the zinc tank. While these colors used to signify different levels of toxic hexavalent chromium, modern trivalent systems use color primarily for identification and specific corrosion targets.
1. Blue / Clear Passivation
- Appearance: A bright silver finish with a slight blue iridescent tint.
- Performance: Typically provides 24-48 hours of salt spray resistance to white rust.
- Application: Indoor hardware, consumer electronics, and where a “bright metal” look is preferred.
2. Yellow Passivation
- Appearance: An iridescent gold/yellow color.
- Performance: Modern trivalent yellow is a “thick-film” passivation, typically providing 72-120 hours of salt spray resistance.
- Application: Automotive engine components, heavy machinery, and parts needing a visible indicator that they are plated.
3. Black Passivation
- Appearance: A deep, matte or semi-gloss black.
- Performance: Highly variable, but generally matches yellow passivation (96+ hours) when paired with a sealer.
- Application: Visible automotive fasteners, solar panel frames, and tactical equipment.
Summary: Which to Specify?
If you need the highest corrosion resistance, Yellow (Thick-Film) is generally the industrial standard. If you need a premium silver look, choose Blue/Clear. For any outdoor or automotive application, always specify an additional Topcoat Sealer regardless of the color.
All Platinex zinc passivations are 100% RoHS-compliant Trivalent (Cr3+) formulations. Contact us to view samples of our Blue, Yellow, and Black finishes.