How zinc plating prevents rust
Zinc electroplating deposits a thin zinc layer on steel. Zinc acts as a sacrificial anode — it corrodes instead of the steel, so the base metal stays rust-free even if the coating is scratched.
That is why zinc-plated screws, nuts and bolts resist corrosion economically — ideal for general indoor and protected outdoor use.
Passivation and coating color
After plating, a passivation step adds a thin chromate film that boosts corrosion resistance and sets the color.
- Yellow/Iridescent — high corrosion resistance; popular in industry.
- Clear/Blue — clean appearance; moderate corrosion resistance.
- Black — for appearance and reduced glare.
- Olive Drab — highest corrosion resistance in the group; military/heavy use.
Cr3+ vs Cr6+ — why switch
Passivation once used Hexavalent Chromium (Cr6+), a carcinogen banned under RoHS and REACH.
Today we use Trivalent Chromium (Cr3+), which gives comparable or better corrosion protection while being safe for people and the environment. V.S. Heat Treatment runs an all-Cr3+ line and offers White Zinc, Blue Zinc and Yellow (rainbow) Zinc to match each customer’s use and budget.
Top coat / sealer for longer life
A top coat or sealer over the passivation multiplies salt-spray life and helps control thread friction (torque-tension) on fasteners needing consistent clamp load.
FAQ
How many hours of corrosion resistance?+
Depends on passivation and top coat; typically 72–500+ hours in salt spray. Specs can be set to your need.
Is zinc plating OK outdoors?+
To a degree. For high humidity/salt, consider thicker coating or a Geomet/Dacromet system.
