Anti-corrosion Methods for Chemical Plants

From:Linshang Time:2020/04/02 11:30:00 Browse:139
Anti-corrosion methods can be divided into two categories in general: one is the correct selection of anti-corrosion materials and anti-corrosion measures; the other is the selection of reasonable process operations and equipment structures.

Strict adherence to the process rules for chemical production can eliminate corrosion that should not occur, and even if a good corrosion-resistant material is used, non-corrosion rules in the operation process will cause severe corrosion. At present, there are several common anti-corrosion methods in chemical production.

1. Anticorrosive methods for chemical plants

(1) Correct material selection and design

Understanding the corrosion resistance of different materials and choosing the correct and reasonable anti-corrosion materials is the most effective method. As we all know, there are many types of materials. The corrosion rates of different materials in different environments are also different. The material selector should choose materials that meet the design requirements, such as low corrosion rate, cheaper prices and physical and mechanical properties.

(2) Surface treatment

The metal is treated with a passivation agent or a film-forming agent before contacting the use environment. A stable and dense passivation film is formed on the surface, and the corrosion resistance is greatly increased. It differs from the corrosion inhibitor method in that it does not need to be added in the future environment. Aluminum is anodized, and the surface can form a denser film than that generated in the atmosphere. Excellent corrosion resistance in a mild corrosive environment. This is also the principle of blueness on the surface of steel parts.

(3) Metal plating and coating

A thin layer of more corrosion-resistant metal can be used on the steel substrate. The commonly used method is electroplating. Generally, 2 to 3 layers are plated, only a few tens of micrometers thick. Therefore, micropores inevitably exist. The solution can penetrate the micropores, which will form a plating layer and a bottom corrosion cell. If the coating is a noble metal, its potential is higher than that of iron, which will become the cathode and accelerate the corrosion of the underlying iron. Therefore, this type of coating is not suitable for strongly corrosive environments, but can be used in the atmosphere, water and other environments. The slowly generated corrosion products can block the micropores, increase the resistance and obtain a certain service life. If an inexpensive metal is used, the polarity of the corrosion cell is reversed, so that the steel is cathodicly protected and the life can be maintained for a long time. In addition to electroplating, hot dip (melt dip), flame spraying, steam plating, and monolithic sheet metal plating are also commonly used. The latter has no microporosity, strong corrosion resistance and longer life, but the price is slightly higher.

(4) Coating

Protecting metallic structures in the atmosphere with organic coatings is the most widespread means of corrosion protection. The coating covers the metal surface and forms a porous film after drying. Although the metal cannot be completely isolated from the medium, it increases the diffusion resistance and resistance of the solution through the micropores, which reduces the corrosion current. In a mild environment, such as the atmosphere, seawater, etc., the metal at the bottom of the micropores corrodes slowly. The corrosion products can block the micropores and have a long service life. However, it is not suitable for strong corrosion solutions, because the metal corrosion rate is fast and accompanied The generation of hydrogen will rupture the paint film.

2. Chemical plant anticorrosive coating thickness detection

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For the measurement of anti-corrosion coating thickness, Linshang Technology LS223 paint thickness tester is recommended. The paint thickness tester uses the principle of eddy current and Hall effect to accurately measure the thickness of non-magnetic coatings on magnetic metals and the thickness of non-conductive coatings on non-magnetic metal substrates. LS223 paint thickness tester can be widely used in the shipbuilding industry, hardware, metal processing industry coatings and anti-corrosion coating thickness measurement. The LS223 paint thickness teser use separate design and can view the data while measuring in a complex environment. The paint thickness tester can accurately and non-destructively measure the coating thickness, which can be used in engineering sites and laboratories.

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