Text Box: Roften Galvanizing Limited
Registered Office & Contact Address: North Road Industrial Estate, Ellesmere Port, Cheshire. CH65 1AB Registration No. 1290735

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Text Box: Venting & Design

Vent/drainage holes are required in all tubular fabrications that are to be galvanized. Drainage holes are also required in channel, angle and RSJ sections, were the welding together of the sections forms pockets that would trap zinc or air.

The correct placement of holes is an important factor affecting both the quality of the zinc coating and the weight of zinc that is applied to the work. 

The table across shows the minimum size of hole required. 


Text Box: Vent Holes — “The bigger the better”
Text Box: Why are Vent Holes Important?
Safety Notice:
Water or other solutions can enter hollow sections during fabrication or during the galvanizing process.  When the steelwork  is dipped into the zinc bath (which is heated to 450 degrees C) the water is converted into steam.  This results in the solution/water expanding approximately 1750 times its original volume.  Pressures of 50MPa can be produced!

To contact us call: 0151-355 5757   Email: sales @roften.com


Hot Dip Galvanizers, Shotblasters, Industrial Painters, Access Covers & Frames

Galv Design Info

Size of Hollow Section

Diameter of Vent/Drainage Holes










Please consult with us