Most people assume a chrome-plated part resists rust because of the bright chrome on the surface. It is almost the opposite. On decorative chrome, the corrosion protection comes from the nickel underneath. The surface chrome is thin and microporous; the nickel is what actually holds back corrosion. Get this wrong and the part rusts within months.
Why nickel does the protecting
The decorative chrome layer is very thin and has micropores, so it cannot seal the substrate on its own. The nickel layer is thicker and denser, and it is the main barrier against the corrosive medium. Nickel thickness, therefore, largely sets the corrosion life of a decorative part.
Nickel thickness vs service environment
| Environment | Nickel requirement |
|---|---|
| Indoor, dry (lighting, furniture parts) | Standard nickel thickness |
| Bath, kitchen (humid) | Heavier nickel |
| Outdoor / high humidity and salt | Increased nickel, duplex nickel recommended |
Duplex nickel: a corrosion upgrade
Duplex nickel (semi-bright nickel plus bright nickel) uses the potential difference between the two layers so that, even when corrosion starts, it spreads sideways rather than driving straight down to the substrate. This significantly extends life and is a common system for bath and outdoor parts.
Copper-nickel-chrome systems
Some parts get a copper strike before nickel to improve leveling and adhesion, forming a copper-nickel-chrome stack that balances appearance and corrosion. The right system depends on the part and the budget.
Advice for buyers
Do not just write "chrome plating." Specify the nickel thickness and whether you require duplex nickel, and agree a salt spray duration. Those are the things that actually decide whether the part rusts. See nickel plating and chrome plating.
FAQ
If a chrome part rusts, is the chrome to blame?
Usually it is insufficient nickel underneath or a pretreatment problem, not the surface chrome.
When do I need duplex nickel?
For bath, outdoor, and high-humidity, high-salt applications where corrosion demand is high.
Can you do duplex nickel?
Yes. We design the coating system to your corrosion requirement and control nickel thickness. Request a quote.