Domestically produced hot-dip galvanized steel sheets are widely used in construction, automotive, and home appliance industries for corrosion protection. Their anti-rust performance is primarily determined by the thickness of the zinc coating. According to the national standard GB/T 2518-2019 "Continuously hot-dip zinc and zinc alloy coated steel sheet and strip", the coating mass is designated by a "Z" followed by a number, indicating the total coating mass on both sides in g/m². Common designations range from Z60 to Z275. Two main production processes exist: hot-dip galvanizing (thicker coating, 60–300 g/m² per side, robust adhesion) and electro-galvanizing (thinner coating, 10–50 g/m² per side, uniform surface).
Different zinc coating thicknesses provide varying levels of corrosion resistance. The table below summarizes the coating mass, one-side thickness, and recommended applications for each designation:
| Designation | Total both-side coating mass (g/m²) | One-side thickness (μm) | Corrosion resistance and recommended environment |
|---|---|---|---|
| Z60 | ≥60 | ≈4.2 | General indoor (dry, non-corrosive); e.g. light steel framing, electrical cabinets – not suitable for outdoor use. |
| Z80 | ≥80 | ≈5.6 | Dry indoor or short-term outdoor exposure; e.g. interior wall panels, ventilation ducts. |
| Z100 | ≥100 | ≈7.0 | General outdoor (non-coastal, non-heavy industrial); expected service life ~10 years; e.g. billboards, guardrails. |
| Z120 | ≥120 | ≈8.4 | Outdoor moderate corrosive environment (coastal or industrial atmosphere); better than Z100. |
| Z140 | ≥140 | ≈9.8 | Moderate corrosion (suburban, chemical workshops); life 30–50% longer than Z100. |
| Z180 | ≥180 | ≈12.6 | High corrosion (coastal tidal zones, heavy industrial areas, acid rain); expected life >20 years. |
| Z220 | ≥220 | ≈15.4 | Severe corrosion (high salt spray coastal areas, offshore structures, chemical contact). |
| Z275 | ≥275 | ≈19.2 | Extreme corrosion, design life >25 years; e.g. highway barriers, solar racking, port equipment. |
Note: Thickness calculated using zinc density 7.14 g/cm³. Hot-dip process achieves the above values; electro-galvanizing typically gives ≤7 μm per side (for Z100 and below).
Summary of corrosion resistance: Z60–Z80 are limited to indoor or short-term outdoor use; Z100–Z140 are common cost-effective outdoor choices; Z180 and above are suitable for critical components with design life >20 years or C5 corrosive environments. For extremely aggressive conditions (islands, chemical plants), aluminized zinc (e.g. AZ150) or zinc-aluminum-magnesium coatings are recommended, offering 2 to 6 times the corrosion resistance of conventional galvanized coatings.
The Galvanized + Powder coated Waste Containers from our company, PG&GP, are manufactured using hot-dip galvanized steel sheets. After forming, they receive a final powder coating, creating a robust anti-corrosion and anti-rust barrier. This dual-layer protection effectively prevents corrosion and rusting caused by outdoor exposure to wind, rain, and sunlight.
