Galvanized cable trays must meet specific standards for zinc coating thickness, corrosion resistance, material type, and installation conditions, with hot-dip galvanization preferred for harsh environments.

Material and Construction Requirements

Galvanized cable trays are typically made from carbon steel and must be protected against corrosion. The trays are prefabricated in various types such as ladder, trough, or channel trays, with rung spacing and tray width following standards like NEMA VE-1 for ladder and trough types, and channel trays not exceeding 150 mm in width for solid or ventilated bottoms . The sheet metal thickness usually ranges from 1.5 mm to 3 mm, depending on the tray type and load requirements .

Galvanization Methods

There are two main galvanization processes for cable trays:

1. Electro-Galvanization (Electrolytic)

   • Deposits a thin, uniform zinc layer on the steel surface.
   • Minimum zinc thickness: 12 µm, suitable for dry indoor environments.
   • Provides limited corrosion resistance and is not recommended for outdoor or marine environments .

2. Hot-Dip Galvanization (HDG)

   • Steel components are submerged in molten zinc, forming a zinc-iron alloy layer and a pure zinc layer.
   • Minimum zinc thickness: 45 µm, corresponding to a coating mass of ≥325 g/m².
   • Offers superior corrosion resistance, ideal for outdoor, coastal, or industrial environments .
   • Coating must comply with standards such as ASTM A123/A123M with Coating Grade 65, providing an average zinc coating weight of 460 g/m² per side or thickness of 0.065 mm per side .

Corrosion Protection and Maintenance

• Cuts or damaged areas of hot-dip galvanized trays must be repaired with compatible materials to maintain coating integrity .
• Corrosion-inhibiting compounds should be applied at junctions of dissimilar metals (e.g., aluminum and galvanized steel) to prevent galvanic corrosion in wet environments .
• Electro-galvanized trays are unsuitable for sea freight or humid marine conditions, as thin coatings can develop white or red rust during transport .

Standards and Compliance

• NEMA VE-1: Specifies manufacturing, load/span designations, and tray types for metal cable trays .
• CSA C22.2 #126.1: Harmonized with NEMA VE-1 for Canadian applications .
• IEC 61537: International standard for metal cable tray systems, including testing and performance requirements .
• GB/T 13912-2020: Specifies hot-dip galvanized coating requirements for fabricated steel articles .
• GB/T 26941.1-2011: Defines electro-galvanized tray requirements .

Summary

To comply with galvanized cable tray requirements:

• Use carbon steel with appropriate tray type and dimensions.
• Select hot-dip galvanization for outdoor or corrosive environments; electro-galvanization is limited to indoor dry conditions.
• Ensure minimum zinc thickness and coating mass per applicable standards.
• Repair damaged coatings and apply corrosion inhibitors at dissimilar metal junctions.
• Follow NEMA, CSA, IEC, ASTM, and GB/T standards for manufacturing, installation, and maintenance .