Requirements for galvanizing cable trays

Cable trays must be galvanized according to the environment and standards, with hot-dip galvanization preferred for outdoor or corrosive conditions and electro-galvanization suitable for dry indoor use.

Types of Galvanization

1. Hot-Dip Galvanization (HDG)
   • Involves submerging steel components in molten zinc, forming a zinc-iron alloy layer and a pure zinc layer .
   • Provides thick, durable, and highly corrosion-resistant coating, ideal for outdoor, industrial, or coastal environments .
   • Coating should be continuous, uniform, and smooth, with minor dull or light grey areas permissible, but defects like bare spots, blisters, or excessive zinc dross are not allowed .
   • Standard: GB/T 13912-2020 and ASTM A123/A123M, with a typical zinc coating weight of 460 g/m² per side (0.065 mm thickness) for carbon steel .
   • Damaged areas must be repaired with compatible materials to maintain coating integrity .
2. Electro-Galvanization (Electrolytic Zinc Coating)
   • Deposits a thin, bright, uniform zinc layer via electrolysis .
   • Provides limited corrosion resistance, suitable mainly for dry indoor environments .
   • Minimum zinc coating thickness: 12 µm .
   • Not recommended for sea freight or humid environments, as thin coatings can develop white or red rust quickly .
   • Standard: GB/T 26941.1-2011.

Material and Environmental Considerations

• Carbon Steel Cable Trays: Must be protected against corrosion using HDG for outdoor or corrosive environments, or electro-galvanization for indoor dry conditions .
• Aluminum Cable Trays: For outdoor use, anodized aluminum is preferred; PVC coatings are not allowed for galvanized steel or aluminum trays .
• Corrosive Environments: HDG is mandatory for areas with severe alkaline or acidic conditions .
• Junctions of Dissimilar Metals: Apply approved corrosion-inhibiting compounds to prevent galvanic corrosion .

Mechanical and Installation Requirements

• Cable trays must comply with NEMA VE-1 or equivalent IEC standards .
• Must have adequate mechanical strength and rigidity, free of sharp edges or burrs that could damage cables .
• Allowable load capacity: static weight of cables plus 20% spare .
• Hot-dip galvanized trays should be repaired at cuts or damaged areas to maintain corrosion protection .

Summary

• Hot-dip galvanization: Preferred for outdoor, industrial, or corrosive environments; thick, durable coating; ASTM A123/A123M or GB/T 13912-2020.
• Electro-galvanization: Suitable for indoor dry environments; thin coating (≥12 µm); GB/T 26941.1-2011.
• Repair and maintenance: Ensure coating integrity at cuts, junctions, and damaged areas.
• Material choice: Carbon steel with HDG or electro-galvanization; aluminum anodized for outdoor use. Proper selection of galvanization type ensures long service life, corrosion resistance, and compliance with mechanical and safety standards for cable tray installations .