The national standard for galvanized cable trays typically requires hot-dip galvanizing with a zinc coating thickness of 45–55 µm (325–460 g/m²), depending on tray thickness and environmental conditions.

Zinc Coating Requirements

For hot-dip galvanized (HDG) steel cable trays, the standard specifies a minimum zinc coating thickness of 45 µm (corresponding to a coating mass of 325 g/m²) for typical tray sheets of 1.5–3 mm thickness, while heavier components like brackets may require ≥55 µm (≥460 g/m²) to ensure corrosion resistance . Electro-galvanized trays have a lower minimum thickness of 12 µm, suitable only for dry indoor environments due to limited corrosion protection .

Standards and Specifications

• T/CECS 31-2017 defines technical specifications for steel cable trays, including galvanizing processes and zinc layer thickness .
• NEMA VE-1 and ASTM A123/A123M are commonly referenced for metallic cable trays, specifying hot-dip galvanizing after fabrication with a coating grade of 65 and an average zinc weight of 460 g/m² per side (≈0.065 mm thickness), .
• GB/T 26941.1-2011 applies to electro-galvanized trays, while hot-dip galvanizing is preferred for outdoor or corrosive environments due to superior adhesion, compactness, and durability .

Environmental Considerations

The required zinc thickness depends on service conditions:

• Indoor, dry environments: Electro-galvanized trays with 12 µm zinc may suffice .
• Outdoor or marine environments: Hot-dip galvanized trays with ≥275 g/m² (≈39 µm) coating mass are recommended to prevent white rust during transport and storage .
• Highly corrosive or alkaline/acidic conditions: Hot-dip galvanizing after fabrication is mandatory, and damaged areas must be repaired with compatible materials to maintain coating integrity .

Quality and Appearance

The galvanized coating should be continuous, uniform, and smooth, with minor dull or light grey areas permissible. Defects such as bare spots, blisters, rough nodules, or excessive zinc dross are not allowed . Coating adhesion is verified through tests like the mandrel wrap test, and copper sulfate tests ensure coating density .

Summary

For compliance with national standards:

• Use hot-dip galvanizing for outdoor or corrosive environments.
• Ensure minimum zinc thickness of 45–55 µm depending on component size and exposure.
• Electro-galvanized trays are limited to indoor, dry conditions.
• Follow NEMA VE-1, ASTM A123/A123M, T/CECS 31-2017, and local standards for fabrication, coating, and repair procedures . This ensures durable corrosion protection, long service life, and adherence to national and international specifications.