Zinc coating thickness of hot-dip galvanized cable trays

Hot-dip galvanized cable trays typically require a minimum zinc coating thickness of 45–55 microns, depending on steel thickness and component type.

Standard Requirements

For cable trays, the local zinc coating thickness depends on the steel sheet thickness:

• Side and base plates (1.5–3 mm thick): Minimum 45 µm, corresponding to a coating mass of at least 325 g/m².
• Heavier components (brackets, supports >3 mm): Minimum 55 µm to ensure adequate corrosion protection . These values are based on international standards such as UNI EN ISO 1461 and local regulations, which define both minimum thickness and mean coating mass for hot-dip galvanized components . The coating must be continuous, uniform, and free from defects like bare spots, blisters, or excessive zinc dross.

Measurement Methods

Zinc coating thickness can be measured using:

• Magnetic thickness gauges: Non-destructive, commonly used for multiple points on the tray surface. Types include pencil-style, banana, and digital gauges .
• Gravimetric (dissection) method: Determines mean coating mass per unit area, often used for arbitration or verification .
• Optical microscopy: Destructive method, used for resolving disputes or detailed analysis . Measurements should ensure that all points meet the minimum local thickness requirement, and the mean coating mass aligns with the standard.

Practical Considerations

• Excessive coating thickness is generally not limited by standards but may cause handling or functional issues if it exceeds approximately 250 µm (10 mils), .
• Inspection and quality control are essential to verify uniformity, adherence, and compliance with standards. Minor surface irregularities like dull areas or passivation films are acceptable, but functional defects are not .

Summary

For hot-dip galvanized cable trays, ensure a minimum zinc coating of 45–55 µm, depending on component thickness, measured using magnetic gauges or gravimetric methods. Compliance with ISO 1461 and local standards guarantees corrosion protection, durability, and functional reliability of the trays in service .