In modern industry and construction, hot-dip galvanized pipes are widely used due to their excellent corrosion resistance and long service life. However, with the prosperity of the market, different qualities of hot-dip galvanized pipes have emerged, and how to identify their quality has become a major challenge for users and buyers. This article will start from the basic concept of hot-dip galvanized pipe, and in-depth identification methods to help you better understand and select high-quality hot-dip galvanized pipe.
First, the basic concept of hot-dip galvanized pipe
1. Definitions. Hot-dip galvanized pipe refers to a steel pipe that is treated by a hot-dip galvanizing process, and its surface is coated with a layer of zinc. This process is mainly to improve the corrosion resistance of steel pipes and prolong their service life. In the hot-dip galvanizing process, the cleaned steel pipe is completely immersed in the molten zinc to form a zinc layer on the surface, so as to achieve the purpose of corrosion resistance.
2. Application field.
Hot-dip galvanized pipes are widely used in construction, machinery, coal mines, chemical industry, electric power, rail vehicles, highways, bridges, containers, sports facilities, agricultural machinery, petroleum machinery, exploration machinery and other fields.
2. Identification method of hot-dip galvanized pipe
1. Observe the appearance.
1) Zinc layer uniformity.
The galvanized layer on the surface of high-quality hot-dip galvanized pipes should be uniform and consistent, without dripping, missing plating or excessive galvanizing. The uniform zinc layer can effectively prevent local corrosion and prolong the service life of the pipe.
2) Surface finish.
The surface of high-quality hot-dip galvanized pipe should be smooth and free of zinc scars, scratches and other physical damage. The surface finish not only affects the aesthetics of the pipe, but also directly relates to its corrosion resistance.
2. Check the thickness of the zinc layer.
The thickness of the zinc layer is one of the important factors affecting the corrosion resistance of hot-dip galvanized pipes. Typically, the thickness of the zinc layer can be detected by a magnetic thickness gauge. According to the national standard, hot-dip galvanized pipes of different specifications and uses have corresponding zinc layer thickness requirements. Users should choose the appropriate zinc layer thickness standard according to their specific needs.
3. Chemical composition analysis.
In addition to zinc, a small amount of elements such as aluminum (Al), chromium (CR), copper (Cu), etc. will be added to the zinc layer of high-quality hot-dip galvanized pipe to improve the physical and chemical properties of the coating. Through chemical composition analysis, it is possible to determine whether the composition of the galvanized layer meets the relevant standards.
4. Salt spray test.
The salt spray test is one of the effective methods to test the corrosion resistance of hot-dip galvanized pipes. The sample was placed in an environment containing a certain concentration of saline, and the corrosion of the sample surface was observed after a certain period of time. High-quality hot-dip galvanized pipes should have no obvious signs of corrosion on their surface after a long salt spray test.
5. Consult manufacturers and certification inquiries.
When choosing hot-dip galvanized pipes, it is also one of the important ways to identify product quality by understanding the manufacturer's production qualifications, production processes and whether the products have passed national or international certification standards.
3. The difference between hot-dip galvanized pipe and cold-dip galvanized pipe
1. Production process
Hot-dip galvanized pipe: By immersing the steel pipe in a furnace dissolved with zinc, the zinc reacts with the steel at high temperatures to form a zinc-iron alloy layer, and then forms a pure zinc layer on the surface to achieve galvanization. This process usually takes place around 400.
Cold galvanized pipe: Also known as electro-galvanizing, the surface of the steel pipe is coated with a layer of zinc by electrolysis. The process is carried out at room temperature and does not form a zinc-iron alloy layer, which is mainly pure zinc.
2. Plating performance
Hot-dip galvanized pipeThe coating is thick, generally above 35 microns, the coating is tightly combined with the surface of the steel pipe, the coating is uniform, the adhesion is strong, and the corrosion resistance is good. The zinc-iron alloy layer makes the combination of the plating and the steel pipe matrix more firm, and has good wear resistance.
Cold galvanized pipe: The coating is thin, generally between 5-15 microns, the adhesion of the coating is weak, the corrosion resistance is relatively poor, and it is easy to be damaged by the external environment.
3. Application field
Hot-dip galvanized pipeBecause of its good corrosion resistance and wear resistance, it is widely used in construction, machinery, coal, chemical industry, electric power, railway vehicles, ** and other fields. It is especially suitable for outdoor environments, humid areas, and strong corrosive environments.
Cold galvanized pipeDue to its thin coating and weak corrosion resistance, it is mostly used in interior decoration, manufacturing electrical appliances and light industrial products, etc., and is suitable for dry environments.
Hot-dip galvanized pipes are widely used in many fields due to their excellent corrosion resistance and long service life. By observing the appearance, inspecting the thickness of the zinc layer, analyzing the chemical composition, testing the salt spray and consulting the manufacturer, the quality of the hot-dip galvanized pipe can be effectively identified, so as to select the cost-effective product. I hope the introduction of this article can help you choose the right hot-dip galvanized pipe in practical application to ensure the smooth progress of the project.