Hot-dip galvanizing requirements
Protection of steel by immersion in hot zinc has been practiced for several centuries. In the 19th century were first derived requirements for materials, process, results. Today, everything is also applicable hot dip galvanizing, the requirements for which, however, have become much tougher.
The companies process steel in accordance with GOST 9.307-89. The state standard provides a complete regulation of technologically competent work. Much attention is paid to the materials. Galvanizing is subjected to low-carbon steel that meets the requirements of state standards 27772-88, 1050-88, 380-94. The composition of some items of steel shall be the following: carbon, 0.25% silicon, 0.37 percent. Alloy steel is not allowed before galvanizing.
If you really need to may be immersed in the zinc of other types of steel. Be sure to conduct a trial dive. The customer shall evaluate the result, make a decision on further work.
The dimensions of the product or metal sheet are significantly limited by the dimensions of the ceramic bath. The most common size - 1,45 x 2,45 x 12 m. Parts that do not fit into the vessel can not be galvanized correctly. The small size of the product also serves as an obstacle. It is not recommended to process thin steel elements.
The design can be complex, but zinc should flow freely in parts of the parts when applied. The danger is too narrow thread-it is she who is most exposed to corrosion due to the difficulty in applying a protective melt. Drums, coils, plugs present in pipes, boxes or pipes can interfere with the application of zinc.
Can become an obstacle in the performance of hot-dip galvanizing requirements for the state of the product. The preparation process should be carried out carefully. On the surface of the metal structure should not be:
- metal shavings;
- marking paint;
According to the requirements of GOST, the stage of preparation of the product for immersion in zinc solution is carried out multistage, using alkaline, acidic reagents of a certain concentration. Purification is carried out at the desired temperature. Be sure to perform washing. Skipping any stage entails unreliable adhesion of the melt to the structure of the material or corrosion of steel residues of reagents.
Zinc in the ceramic bath is heated to 450 degrees. The holding time of the product in solution is 3-10 minutes. It is important to place the part inside the spinning drum – zinc will lie on the surface of the steel is much smoother and stronger.
Only when all the requirements can be expected to quality results and long service life of the structure.