Galvanised steel is made up of a steel sheet and a zinc coating. The steel sheet rusts when it comes into contact with air, water, etc., so it is coated with a metallic coating to slow down the rusting process. Therefore, when the outer coating of zinc is damaged, the galvanized steel will also rust. The thickness of the zinc coating determines the corrosion resistance of galvanized steel, which currently has a life expectancy of up to 50 years.
How Long Does it Take for GI Steel to Rust?
Galvanized steel can be divided into hot-dip galvanized steel and electro-galvanized steel according to the process. Hot-dip galvanized steel has a thicker of zinc and therefore is more resistant to corrosion, but its lifespan is affected by the humidity, temperature, and concentration of corrosive substances in the environment.
Recommended Zinc Coating for Different Environments
| Use | Recommended |
|---|---|
| Indoor uses | Z10 or Z12 (100 g/㎡or 120 g/㎡) |
| Suburban area | Z20 and painted (200 g/㎡) |
| Urban or industrial area | Z27 (270 g/㎡) or G90 (American Standard) and painted |
| Coastal area | Thicker than Z27 (270 g/㎡) or G90 (American Standard) and painted |
| Stamping or deep drawing applications | Thinner than Z27 (270 g/㎡) or G90 (American Standard) to avoid coating peeling off after stamping |
How to Prevent Galvanized Steel From Rusting?
What can be done to prevent galvanized steel from rusting other than increasing the thickness of the zinc coating? After galvanization, the steel can be surface-treated or coated with other paints to enhance its corrosion resistance.
- Surface treatment: Passivation/oil/paint sealing for fingerprint resistance/phosphatisation.
- Coating: Coating with organic paint, PE/SMP/PVDF/HDP.
How to Extend the Service Life of Galvanized Steel?
What precautions can be taken to extend the service life of galvanized steel?
Firstly, during storage, ensure that the environment is dry and out of direct sunlight.
Secondly, during use, avoid collisions and damage to the zinc coating.
Finally, regular maintenance is required to clean the surface of the galvanized steel from impurities.
Other Coated Steels with Good Corrosion Protection
Wanzhi Group has its production line, providing all kinds of coated steel, gi/gl/ppgi/ppgl etc. If interested, please feel free to send us a message.