블로그 약 New Standards Enhance Galvanized Steel Grating Durability Corrosion Resistance

In infrastructure construction and industrial production, steel grating serves as a crucial structural material widely used in platforms, walkways, and trench covers. However, steel is susceptible to environmental corrosion, which significantly impacts its service life and safety. Hot-dip galvanizing—an economical and effective anti-corrosion method—has become the standard surface treatment for steel grating. This article examines the technical standards, performance characteristics, durability assessments, and common issues with galvanized steel grating.

1. Hot-Dip Galvanizing Process and Standards

Hot-dip galvanizing involves immersing pre-treated steel components into molten zinc to form a zinc-iron alloy layer and pure zinc coating. This metallurgical bond creates exceptional corrosion resistance with strong adhesion to the steel substrate.

International standards govern steel grating galvanization. In China, GB/T 13912-2002 ("Metallic Coatings—Hot Dip Galvanized Coatings on Fabricated Iron and Steel Articles") and GB/T 18226-2000 ("General Rules for Pretreatment of Steel Products Before Coating") specify requirements for coating thickness, adhesion, uniformity, and appearance. Globally, ISO 1461:2009 and ASTM A123/A123M-15 provide similar technical frameworks, though thickness classifications may vary.

Selection of zinc coating thickness depends on application and environment. Heavier coatings are recommended for load-bearing structures or corrosive exposures.

2. Coating Thickness and Zinc Adhesion

Coating thickness directly correlates with corrosion protection. The relationship between thickness (μm) and zinc adhesion (g/m²) follows this formula:

Thickness (μm) = Zinc Adhesion (g/m²) / Zinc Density (7.2 g/cm³)

GB/T 13912-2002 mandates minimum thickness requirements:

• Steel ≥6mm: Average 85μm (minimum 70μm locally)
• Steel 3-6mm: Average 70μm (minimum 55μm locally)
• Steel <3mm: Average 55μm (minimum 40μm locally)

Notably, legacy classifications like HDZT63 (formerly HDZ45, 450g/m²) and HDZT77 (formerly HDZ55, 550g/m²) correspond to approximately 62.5μm and 76.4μm respectively.

3. Durability Assessment

Service life depends on coating thickness, environment, and maintenance:

Atmospheric Exposure

In rural environments, galvanized grating can last decades. Industrial/coastal areas accelerate corrosion due to pollutants/salts. Theoretical estimates suggest:

• HDZT63: 15-30 years (urban/industrial)
• HDZT77: 20-40 years (urban/industrial)

Actual lifespan varies with mechanical wear like vehicle traffic.

Submerged Applications

Water quality, temperature, pH, and flow dynamics complicate underwater durability. Empirical data indicates:

• HDZT63: 4-14 years
• HDZT77: 5-17 years

Splash Zones

Areas subjected to seawater spray experience extreme corrosion (200-1000g/m²/year). HDZT77 coatings may last only 0.5-2.5 years in these conditions, necessitating thicker coatings or supplemental protection.

4. Common Issues and Solutions

White Rust

This white/gray powder (zinc hydroxide) forms in humid conditions. While primarily cosmetic, severe cases can compromise protection.

Prevention:

• Apply passivation treatments post-galvanizing
• Store indoors or use waterproof covers
• Avoid contact with acids/alkalis

Coating Delamination

Peeling occurs from improper galvanizing, inadequate surface prep, or harsh environments.

Prevention:

• Select certified galvanizers
• Ensure thorough degreasing/descaling
• Minimize bending/impact during handling

Color Variation

Natural variations in zinc crystallization may cause visual inconsistencies without affecting performance.

Mitigation:

• Use batches from the same production run
• Maintain consistent process parameters
• Apply paint coatings for uniform appearance

5. Color Treatment Options

While galvanizing provides silver-gray finishes, aesthetic requirements may demand coloring:

Painting

Epoxy, polyurethane, or acrylic coatings offer color variety and enhanced protection. Compatibility with zinc must be verified.

Chemical Conversion

Phosphate or chromate treatments create limited color options with lower durability than paints.

6. Conclusion

Hot-dip galvanizing remains a proven solution for steel grating corrosion protection. Proper specification, installation, and maintenance optimize service life across diverse environments. Emerging technologies like nano-coatings may further advance material performance in future applications.