Galvanized (Zinc plated) Bundy tubes are used a lot in automotive and ACR industry, with advantages such as better duration before rust, being economic to replace copper tubes in some sections of the systems, and higher allowable working pressure and burst pressure.
The zinc plating for Bundy tubes can be finished with different corrosion protection performances, followed by chromium passivation (chromate treatment), with no hexavalent chromium used.
The following table shows the data of the performance.
Zinc Thickness, μm min | Passivation | NSS* Test, hr min | |
White Rust | Red Rust | ||
8 | White/Light Blue | NA | 96 |
8 | Yellow/Aurora | 72 | 168 |
8 | Dark/Olive Green | ||
13 | White/Light Blue | NA | 144 |
13 | Yellow/Aurora | 72 | 216 |
13 | Dark/Olive Green | ||
25 | White/Light Blue | NA | 240 |
25 | Yellow/Aurora | 72 | 312 |
25 | Dark/Olive Green |
* Neutral Salt Spray