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General and technical conditions for hot-dip galvanizing
1. Material selection
⦁ Silicon has the greatest influence on galvanizing, as well as its combination with phosphorus:
a) 0 (%) ˂Si (%) ≤0.03 (%) i
Si (%) + 2.5P (%) ≤0.09 for hot rolled material
Si (%) + 2.5P (%) ≤0.04 for cold rolled material
b) 0.13 (%) ˂Si (%) ˂0.20 (%)
⦁ Cast iron should be sandblasted. Gray cast iron is difficult to galvanize well (impossible in combination with structural steel).
⦁ It is desirable that the customer submits a certificate of the material used in the construction, otherwise the galvanizer can not take responsibility for the quality and appearance of the coating. Disadvantages such as gray or mottled coating, intense roughness and peeling of the coating, which are the result of the use of inappropriate material, are not accepted in the complaint.
⦁ If a particular assembly consists of several different materials, the consequences may be different appearance and properties of the coating. The galvanizer is not responsible for the non-uniformity of the coating properties.
2. Workpiece preparation
⦁ The galvanizer is not responsible if the workpiece is not properly prepared, ie it does not have adequate drainage and ventilation openings, and the system for hanging materials (also applies to the case when they are not properly dimensioned). According to the agreement with the customer, the galvanizer can perform the finishing with an appropriate fee. Otherwise it is the buyer's responsibility.
⦁ The threads must be protected or re-threaded after galvanizing. Unless otherwise agreed, this operation is not the responsibility of the galvanizer.
⦁ Separatable or disassembled parts can remain sealed with zinc melt and thus lose their function (need to be galvanized separately). The galvanizer does not take responsibility in such a case.
In cases when it is impossible to control the existence of openings (in the case of internal penetration systems), the buyer is obliged to submit drafts and a written guarantee in which he assumes responsibility (in case of explosion) for the damage or delay.
3. One-sided galvanizing of closed structures
⦁ The buyer is obliged to make a pressure test at 200 kPa (2 bar), and to submit a certificate or a written guarantee for testing. The test should be performed by air. If different oils are used for testing, ignition may occur at the time of immersion in the zinc melt, and they are unacceptable for this purpose.
⦁ For galvanizing such constructions, it is necessary to make special devices, which the customer makes according to the recommendation of the galvanizer.
4. Surface cleanliness
⦁ The surface of the material must not have rolled emulsions or impurities, scaling and doubleness. Cutting or punching areas must be cleaned of cracks and sawdust. We do not accept complaints for coating miscarriage caused by these errors.
⦁ Impurities that cannot be removed by chemical preparation must be removed from the surface of the material, and previous zinc coating has to be removed. Impurities are often not noticeable before performing the galvanizing process. If the quality of the coating is not acceptable, so the galvanizing process needs to be repeated, the additional cost is charged to the customer.
⦁ Welds must be non-porous, continuous and free of slag. Such places remain non-galvanized or residual acid can subsequently leak from them, and this defect is not accepted as a complaint.
5. Coating thickness
6. Appearance of the coating surface
⦁ The surface of the coating should be uniform, without sharp edges. Minor lumps and blisters may occur. Each special requirement for the appearance and quality of the coating is subject to special contracting.
⦁ The surface of the coating may have a matte gray instead of a glossy appearance, and this appearance is not a reason for complaint.
⦁ The galvanizer is not responsible for leaks as a result of porous or discontinuous welding.
⦁ The appearance of white rust during storage after galvanizing cannot be a reason for complaint.
⦁ When painting or plasticizing galvanized material, the customer must additionally mechanically process the surface, because the surface obtained by hot-dip galvanizing according to EN ISO 1461 is not smooth enough for this purpose. This is not the responsibility of the galvanizer.
7. Thermal deformations
⦁ The galvanizer cannot be affected and is therefore not responsible for deformations of the structure caused by residual stresses in the material or due to uneven thermal expansion within the subassemblies (inappropriate design, use of materials of different thickness or incorrect welding procedure).
8. Non-galvanized places
The total non-galvanized surface can be at most 0.5% of the total surface of one element, and the individual non-galvanized surface can be at most 10 cm². Non-galvanized surfaces are repaired with a coating with a high content of zinc in a thickness of 30% greater than the surrounding zinc coating.
9. Transport and collection
⦁ Goods delivered for galvanizing must be palletized and loaded so that they are suitable for transport directly to the plant, without the need for additional transhipment or sorting. Unloading should be possible using a forklift or overhead crane (not manually). Otherwise, the galvanizer is not liable for mechanical damage caused by handling the goods.
⦁ The goods are delivered within the galvanizing facility, unless otherwise agreed.
⦁ In case of improperly prepared galvanizing material, the delivery time is calculated from the day of solving of defects.
⦁ If goods are not taken over within 7 days from the date of issuance of the invoice, we charge a daily deposit.