Prestressed steel is stress corrosion under the combined action of stress and corrosion (in the category of galvanic corrosion). It is characterized by the formation of cracks in the metal first, and after the occurrence of internal cracks, stress concentration will be formed, accelerating the development of cracks. Therefore, the anti-corrosion of prestressed steel wires and steel strands is a major issue related to the quality and life of the project, and we must pay sufficient attention to it. The following are the anti-corrosion measures for prestressed concrete steel strands
The factors affecting stress corrosion are mainly composed of internal and external components, such as the composition and state of the metal, the nature and size of the load, the surrounding conditions of the mental stress, and the physical and chemical properties of the medium. From the internal conditions of the steel, it is required that this type of steel must be refined outside the furnace, and the content of impurities, phosphorus, and copper should be strictly controlled, and the surface defects of the wire rod should also be strictly controlled.
The anticorrosive plating (coating) steel of prestressed steel is always in service under the condition of corrosive medium. Therefore, the manufacturer should deal with it in advance to isolate (or slow down) the medium corrosion of the steel base.
A non-metal protective layer (coating)
The non-metallic coatings of the non-metallic protective coating steel strand for prestressed concrete mainly include plastic, epoxy resin, and anti-corrosion grease. Because of its simple process equipment, low investment, and easy deployment. However, the anti-aging problem of non-metallic coating has not been solved, and its mechanical properties are much lower than that of metal coating. Therefore, the scope of application is limited.
Chemical protection layer
The chemical protective layer forms a protective layer on the metal surface through a chemical method, such as passivation of the zinc layer and oxidation of the aluminum layer. Iron-based phosphating, etc. This type of protective layer is often not used as a single steel strand protective layer but is used in conjunction with the metal coating.
A metal protective layer (plating layer)
In the electrochemical corrosion of the metal protective coating, the metal in the anode is first dissolved. For this reason, the surface of the steel strand is plated with iron and active metals, such as zinc and aluminum. In the environment of corrosive medium, the zinc is first dissolved to protect the iron base, which is called anode coating protection. Cathodic protection (such as tin plating) is rarely used in prestressed steel. Because galvanizing (or zinc-aluminum alloy) has good results and mature process equipment in metal anti-corrosion. Therefore, it is also widely used with prestressed steel.
Prestressed concrete steel strands work under high pressure, and stress corrosion will directly affect their service life and thus the life of construction projects. Therefore, it is very important to have an excellent anticorrosive coating for prestressed concrete steel strands. If you want to know more about prestressed concrete strands after reading the above content, you can contact us for a more comprehensive solution.
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