What is hot dip galvanizing?
Hot dip galvanizing is the best way to protect cast iron and steel against corrosion, both for economic and environmental reasons. No other protection has such durability, corrosion resistance and resistance to mechanical damage. This is due to the specificity of the technology - when immersing the detail in a zinc bath, liquid zinc diffuses into the material, creating an alloy layer. After the item is removed from the zinc bath, a pure zinc coating remains on the outside of the alloy surface. This method allows the elements to be evenly and accurately covered with a layer of zinc, which, thanks to the specificity of the method, reaches even hard-to-reach places.
Hot dip galvanizing in our company?
Our zinc coatings comply with the requirements of PN-EN ISO 1461: 2000. The excellent quality and high aesthetics of zinc coatings obtained in our company are the result of a combination of many factors: many years of experience of the staff, the use of electrolytic zinc with a very low content of impurities (in accordance with the PN-EN 1179: 1998 standard) and modern technology. We have a comprehensive production line, which consists of:
- high-class shot blasting machines (chamber and drum) manufactured by reputable western companies - they carry out preliminary surface preparation of the material using the abrasive blasting method
- the pickling line, on which the surface of details subjected to the hot-dip galvanizing process is prepared - it consists of degreasing and etching baths and fluxing baths
- stationary galvanizing furnaces filled with liquid zinc, in which details previously prepared in the process of abrasive blasting and chemical processing are immersed
- stationary centrifuges - used to centrifuge threaded elements and small fasteners from excess zinc
- cooling water baths in which workpieces are cooled.
The condition for obtaining a satisfactory quality of the zinc coating is, among others:
- the use of a material whose chemical composition allows the proper course of the etching and galvanizing process,
- appropriate construction of the product,
- providing material free from impurities that impede or prevent the etching process, or galvanization.
Design requirements:
- the shape of the product must allow the excess zinc to flow freely while emerging from the bath,
- the products must not have closed spaces, technological openings (venting and drainage) should be provided in closed profiles or containers,
- all elements of the structure, permanently connected to each other, should be made of one grade of steel and with the material thickness of the same type as possible
- products should have handles that allow them to be hung.
On the surface of the material there must not be:
- paint
- excessive corrosion
- welding slag residue
- welding spatter
- rolls, scale, scale
Type of material:
Products made of structural steel in grades St3S, St3SX, St4S, St4SX, 18G2, 18G2A or their equivalents, e.g. S235JRG2, S275JR, S355JR can be galvanized. However, the essential condition for obtaining a bright, smooth and homogeneous zinc coating is the selection of steel according to the chemical composition compliant with the following requirements.
The silicon content in the steel intended for hot-dip galvanizing must be below 0.03% or be in the range from 0.12 to 0.25%.
In the case of zinc coating of products made of steel with a different chemical composition, the obtained zinc coating will be gray, dull, rough, uneven and heterogeneous, and in extreme cases impossible to apply (Sandelin effect).
Similar effects may appear when the steel has a different chemical composition, especially in the surface layer.
The silicon content in the steel intended for hot-dip galvanizing must be below 0.03% or be in the range from 0.12 to 0.25%.
In the case of zinc coating of products made of steel with a different chemical composition, the obtained zinc coating will be gray, dull, rough, uneven and heterogeneous, and in extreme cases impossible to apply (Sandelin effect).
Similar effects may appear when the steel has a different chemical composition, especially in the surface layer.
Hot dip galvanizing steps:
1. Degreasing
2. Digestion
3. Rinsing
4. Fluxing
5. Drying
6. Galvanizing
Process openings diameters depending on the profile and section size:
| Closed profile dimensions smaller than: [mm] | The minimum diameter of holes at the ends of the profile for the number of holes [mm] | ||||
|---|---|---|---|---|---|
 |
 |
 |
1 | 2 | 3 |
| 15 | 15 | 20x10 | 8 | ||
| 20 | 20 | 30x15 | 10 | ||
| 30 | 30 | 40x20 | 12 | 10 | |
| 40 | 40 | 50x30 | 14 | 12 | |
| 50 | 50 | 60x40 | 16 | 12 | 10 |
| 60 | 60 | 80x40 | 20 | 12 | 10 |
| 80 | 80 | 100x10 | 20 | 16 | 12 |
| 100 | 100 | 120x80 | 25 | 20 | 12 |
| 120 | 120 | 160x80 | 30 | 25 | 20 |
| 160 | 160 | 200x120 | 40 | 25 | 20 |
| 200 | 200 | 260x140 | 50 | 30 | 25 |
