Every so often a customer sends us a rusted part and asks: it was chrome plated, how did it rust in a few months? There is a very common misconception here. People assume a chrome part resists rust because of the bright chrome on the surface. It is the opposite. The nickel underneath does the work. Once you understand that, troubleshooting has a direction.
1. The nickel is too thin (most common)
On decorative chrome, most of the corrosion resistance is in the nickel. If the nickel is too thin, the corrosive medium reaches the substrate quickly and the part rusts, especially in humid or outdoor use. So the first thing to check on a failure is whether the nickel thickness was adequate.
2. Pretreatment was not thorough
Residual oil or oxide leaves poor adhesion and microscopic defects, and rust starts at those points. Pretreatment is the foundation of plating; cut corners here and no amount of thickness saves it. It is also the shared root cause of peeling and localized rust spots.
3. No passivation or sealing
Passivation and sealing add a protective film on top of the deposit and noticeably raise corrosion resistance. Skip that step and both the salt spray result and real-world life drop.
4. Wrong system for the substrate
Zinc die-cast, steel, and copper each need a different coating system. Pick the wrong one, for example chrome straight over insufficient nickel on a steel part, and rust is almost guaranteed.
Quick diagnostic
| Symptom | Likely cause |
|---|---|
| Overall dullness, rust in many spots | Thin nickel / no passivation |
| Blistering, then rust | Incomplete pretreatment |
| Edges and weld points rust first | Uneven current, bare spots |
How to avoid it at the source
Corrosion resistance does not come from a bright finish. It comes from nickel thickness, thorough pretreatment, and passivation, the unglamorous fundamentals. When you order, do not just write "chrome." Put the nickel requirement and the salt spray duration in the spec. Those are what decide whether the part rusts.
FAQ
If a chrome part rusts, is the chrome to blame?
Usually not. It is more often insufficient nickel underneath or a pretreatment problem.
Can an already-rusted part be fixed?
Generally it has to be stripped and re-processed from pretreatment; you cannot patch it locally.
How do you control corrosion resistance?
We control nickel thickness, strengthen pretreatment and passivation, and verify by salt spray. Ask for a solution.
If your part has corrosion requirements, or you have had rusting problems, send us the details and we will help trace it back to the process.