Causes of metal corrosion in hardware processing
Published on:
2021-11-19
There are many factors that cause corrosion of steel structures, mainly electrochemical corrosion. Once the steel structure corrodes, it will become more and more serious. In this way, the cross-sectional area of the component will be reduced. The bearing capacity will be reduced, and its use value will be gradually lost and scrapped. Although corrosion is unavoidable in steel structures currently in use. However, the corrosion rate can be controlled, which requires effective anti-corrosion measures for the steel structure.
Characteristics of metal corrosion in hardware processing: After shot peening, pressing, electric welding, and assembly, the internal thermal stress or grain deformation of the steel structure is unevenly distributed, resulting in a potential difference inside the steel structure. It is the "hidden danger" of steel structure corrosion, which is also the reason why steel structure electric welding is particularly prone to rust.
Metal working metal corrosion is caused by a variety of internal and external factors. In summary, there are five main factors that affect the corrosion of metal processing metals.
The influence of metal processing metal material itself
Different metal processing metals have different potentials and different metallographic structures, and their stability (that is, corrosion resistance) is different, and steels with the same chemical composition have different corrosion resistance due to different heat treatment processes. In addition, uneven distribution of thermal stress or grain deformation during thermal processing during forging, casting, welding, etc., may cause differences in the internal potential of the metal processing metal and accelerate the corrosion of the metal processing metal itself.
Metal processing metal surface finish state
There is also a significant effect on the corrosion rate. Especially in the early days. The smoother the metal surface, the better its corrosion resistance. Rough metal processing metal surface, because the deep concave part is not easy to contact with oxygen. It becomes a positive electrode, and the surface becomes a negative electrode, causing the oxygen concentration cell to corrode.
Influence of ambient temperature
- In general, the corrosion rate of metalworking metals in electrolyte solutions increases with increasing temperature. For example, for every 10°C increase in seawater temperature, the corrosion rate of steel doubles because the electrical reaction increases as the temperature increases. In addition, in continental climate regions, the temperature difference between day and night is large, and the relative humidity in the atmosphere rises again at night. It causes the moisture in the air to condense on the surface of the metal processing metal, providing conditions for the metal processing metal to rust.
Effect of Solution Composition and Concentration
For example, seawater is a natural electrolyte solution containing various salts, which also contains organic matter, sludge, dissolved gas, and decaying organic matter. However, the important factors affecting the corrosion rate of steel are the salinity, high salinity and high conductivity of seawater, corrosion current intensity of macroscopic cells, and corrosion of steel. . In addition, a large amount of chloride ions in seawater will hinder or even destroy the passivation of metal processing metals and promote the corrosion of metal processing metals.
Corrosive media and other factors.
Various corrosive media and other factors will also accelerate the corrosion of metal processing metals. In addition to O2 and H2, the atmosphere also contains N2 and various impurities, such as salt spray near the ocean, SO2 and H2S in chemical industrial areas, various soot, metal processing metal compounds and other salt particles. Once these corrosive media fall on the metal surface of metal processing, It will condense with water and accelerate the corrosion of metal processing metals.
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Sheet metal processing production process
2022-07-06
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