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Chemical composition
The hot-dip zinc plating makes it possible to apply a rust protective coat of zinc to structures made of steel with silicon (Si) content lower than 0.03 % or with the range 0.15% - 0.25 % and in steel grades where the total content of silicon does not exceed 0.5 %.

Surface requirements
The surface of structures should be free from any scale, thick rust layers, weld spalls, weld slag, silicon anti-spall agents, remains of paint, lubricants and oil.

Structure features
A structure should offer a possibility to suspend it by using wires or chains under the traverse.
Its shape should allow for free zinc penetration (inflow) to all surfaces and its free outflow.
The mutual proportions of different thickness materials welded together should not exceed 4 : 1.
Avoid zinc plating of thin, large surfaces of non-reinforced sheets because of risk of surface waving.

Vent holes
Any steel structures made of closed space sections should be equipped with vent holes to allow for free inflow of liquid zinc during submerging and free outflow during emerging from the zinc coating bath. The table below presents sizes and quantities of vent holes required depending on the structure type.

Inner dimensions of closed section in mm lower than: Minimum diameter of holes (mm) at opposite section ends and their quantity:
round square rectangular 1 2 3
15 15 20 x 10 8    
20 20 30 x 15 10    
30 30 40 x 20 12 10  
60 60 80 x 40 20 12 10
60 60 80 x 40 20 12 10
80 80 80 x 60 20 18 12
100 100 120 x 80 25 20 12
120 120 160 x 80 30 25 16
160 160 200 x 120 40 25 16
200 200 260 x 140 50 30 16



The vent holes can be made as triangular or semi-circular openings in section walls.
The drawings below present the rules for laying out vent holes.