Galvanized sheet is one of the most commonly used and important materials for making electrical wire boxes and trunking. Its size, thickness, and coating directly affect the mechanical strength, corrosion resistance, and cost of the product.
Galvanized steel sheets are produced in rolls (steel coils) or large flat sheets, and then cut, stamped, and bent according to the design of the wire box and wire slot.
Roll width: Common types include 1000mm, 1219mm, 1250mm, etc. During production, the most economical and least wasteful roll width will be selected based on the unfolded size of the target product.
Sheet size: Common flat sheet sizes include 1000mm × 2000mm, 1250mm × 2500mm, etc.
86 type wire box (most commonly used):
corresponding to panel size of 86mm × 86mm, the depth of the box body is commonly 35mm, 40mm, 50mm, 60mm, etc.
120 type cable tray:
Width: commonly 50mm, 80mm, 100mm, 150mm, etc.
Height: commonly 40mm, 50mm, 60mm, etc.
Length: The standard length is usually 2 or 3 meters.
Thickness is a key indicator for measuring the quality of wire box trunking, which directly affects its compressive strength, durability, and fire resistance. The unit is usually in millimeters (mm)
Product Type
Common Thickness (mm)
Description and Application Scenarios
Concealed wire box (pre embedded in the wall)
1.0mm to 1.2mm
currently the mainstream high standard thickness, with high mechanical strength, not easily deformed, and firmly bonded with cement after pre embedding.
Surface mounted wire box/small wire slot
0.8mm -1.0mm
suitable for surface mounted or slightly lower strength requirements, with good cost-effectiveness.
Medium sized metal cable trays with a diameter
1.0mm to 1.5mm
used for laying a large number of cables, and better structural strength is required to support them.
Large cable tray/trough type cable tray
1.2mm-2.0mm
used for main power lines, with high load-bearing requirements and a wide thickness range. It is selected according to design and load-bearing requirements.
Attention: There are many low-priced products on the market with insufficient thickness of galvanized steel sheets (such as those labeled as 1.0mm, but actually only 0.6-0.8mm). Special attention should be paid when purchasing, as products that are too thin are prone to deformation, affecting construction and safety.
The purpose of the galvanized layer is to prevent rusting of the galvanized steel sheet. Its quality is usually expressed in grams per square meter (g/m²), which is the weight of the galvanized layer on the surface of the steel sheet. The higher the weight, the better the corrosion resistance.
Zinc flower: a visible shiny pattern formed by zinc grains after galvanizing and cooling, beautiful but uneven on the surface, which is not conducive to subsequent uniform spraying.
Zinc free flower: a uniformly fine coating formed through process control. Wire box trunking generally uses zinc free galvanized sheet metal because its surface is smoother, the coating adhesion is better, and the appearance is more beautiful.
Ordinary environment: commonly used Z60-Z80 (i.e. the total amount of double-sided coating is 60-80g/m², and the single-sided coating is about 30-40g/m²). This can meet the needs of most dry and generally humid environments.
High demand/humid environment: Will use galvanized sheets with Z90-Z120 or even higher weight. For example, in damp environments such as outdoors, basements, and computer rooms, better rust prevention capabilities are needed.
Galvanized sheets undergo post-treatment before leaving the factory to enhance their corrosion resistance and coating properties. Common methods include:
Chromic acid passivation: A colorful passivation film with a slight yellow green color on the surface, which is the most common anti white rust treatment method.
Chromium free passivation: an environmentally friendly treatment process, the surface usually appears blue white or light yellow.
Oil coating: Apply an additional layer of rust proof oil on top of passivation to provide short-term additional protection.
For wire boxes and trunking made of galvanized sheet, you can pay attention to the following points:
Check thickness: Weigh by hand and measure thickness with a caliper. It is recommended to choose 1.0mm or above for concealed wire boxes.
Check the coating: Observe whether the surface is uniform and delicate (preferably without zinc flowers), and whether there are defects such as missed plating and peeling. If possible, you can inquire with the manufacturer about the weight standard for galvanizing.
Check the process: Check whether the coating at the bend is cracked, whether the solder joints are firm, full, and free of burrs.
Brand selection: Choose well-known brands with good reputation for better quality assurance and avoid using "non-standard" products.
In summary, a high-quality galvanized sheet wire box/trunking is usually made of zinc free galvanized sheet with a thickness of 1.0mm or more (coating weight of Z60 or more) and manufactured through good processes.
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