How To Prevent Pressure Vessels From Being Corroded

By Author: DFC Tank Pressure Vessel Manufacturer Co., Ltd
Total Articles: 1
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A pressure vessel is a hermetic device that carries liquid or gas with a large pressure, or fluid that can form a pressure inside or is subjected to external pressure. Common malfunction of pressure vessels and their accessories such as corrosion, cracking, erosion, deterioration, and alteration often cause serious consequences. If corrosion issue is often ignored, even a well-constructed pressure vessel may be damaged or has a shorter service life, and gives rise to a safety accident. So the specific operation and scientific strategies for prevention must be applied.

The main influencing factors of corrosion in pressure vessels

External environmental reasons
The internal and external environment of the pressure vessel will directly affect its corrosion resistance. Pressure vessels can carry a large number of reagents, and the cost of the substances contained therein is high. So it is inevitable that some corrosive materials, such as acidic, and alkaline materials, may be mixed, and these components are likely to cause corrosion of the pressure vessel.

The external environment causes corrosion to ...
... the pressure vessel in various forms. First, when the pressure vessel is corroded during application, the increase of internal pressure will play a significant catalytic role, accelerating the corrosion reaction, and thus deteriorate the corrosion problem. Second, the temperature in the pressure vessel will accelerate the reaction speed because as the temperature rises, the ion flow speed increases. And every 10 ℃ increasing, the chemical reaction rate will accelerate by 2-3 times. Third, the internal acid-base environment will catalyze the reaction rate, and in the different acid-base environment, the internal ion content will be different.

Material characteristics
The material properties of the pressure vessel greatly influence and determine the level of corrosion resistance of the pressure vessel itself. First, the corrosion rate will be affected by the density and oxidizing property of the surface crystal structure. The larger the crystal structure density, the rougher the surface, the larger the intergranular gap, and the more likely the corrosion reaction occurs. Second, when using the pressure vessel, if the internal pressure is high due to the large pressure of importing medium and the internal calcination, the pressure vessel may deform and cause a corrosion reaction. If H2S is inside the vessel, then the pressure vessel is likely to be corroded. Third, if the material composition of the pressure vessel is disordered, the electrochemical corrosion reaction rate will be accelerated. In such a pressure vessel, it is easy to generate the galvanic reaction. If there is an inert material inside, the metal corrosion rate will be accelerated.

Precautions of pressure vessel corrosion

Improve the external environment
Improving the external environment can prevent corrosion of the pressure vessel, which mainly involves two suggestions, one is that it is better not to use pressure vessels in a working environment with high temperature and high humidity. And the other is to adopt electroplating and to add a corrosion inhibitor on the medium. The electroplating method mainly refers to by applying the electrolysis principle, a metal layer that can improve the oxidation is set on the electric conductor so as to effectively prevent stress corrosion.

Choose an appropriate corrosion inhibitor
An appropriate amount of corrosion inhibitor on the metal surface of the pressure vessel can effectively improve the corrosion level and reduce the corrosion rate. The cost of adding corrosion inhibitors is lower than that of other anti-corrosion processes, and the effect is obvious, especially in the case of controlling chemical corrosion and electrochemical reaction corrosion. Corrosion inhibitors are mainly classified into adsorption type, oxide type, and precipitation type. The adsorption type belongs to an organic substance, which can improve the anti-corrosion level of the metal surface of the pressure vessel; the oxide type itself is an oxidant, and can redox-react with the reducing substance in the reagent. The substance will adhere to the inside and create a protective film that reduces the rate of corrosion.

Select materials according to actual conditions
Selecting the right pressure vessel materials can reduce the corrosion of the vessel from the fountainhead. They should be selected according to the application conditions and various standards. First, on the basis of considering the corrosion resistance of the material, it is also necessary to take into account the high temperature and high pressure resistance of the materials, thereby reducing the probability of physical corrosion;

Second, select materials combined with the actual situation and the type of solvent. For example, the solvent is highly reductive or in a very humid environment, it is necessary to prevent the use of steel pressure storage tank; third, select materials in accordance with the relevant standards. Pay attention to the construction of materials. It is better not to use a material with a large intergranular gap so as to prevent corrosion caused by penetration. Carbon steel is usually selected as the material for producing pressure vessels, and copper, titanium can also be used as casting materials.

Research and development of new types of materials
The manufacturing process of pressure vessels is always improving, and new materials are emerging and utilized. At present, the main raw materials used in various pressure vessels are usually metal materials or alloy materials, and composite materials are used in special components with small structures. Because most metal materials and alloy materials have poor acid and alkali resistance, the development and adaptation of new materials should be highly concerned.

Electrochemical protections
Electrochemical protection is to prevent the corrosion reaction on the metal surface of the pressure vessel, turning it into the cathode and then protecting it. At present, there are mainly two methods. One is externally adding a DC power source, changing the direction of the electrons when the metal material is the anode and turning the pressure vessel to the cathode, preventing it from being corroded, which requires a long-term power supply. The current can be adjusted at any time according to the actual conditions. The other method is sacrificial anode. Put active materials that are more easily oxidized than the surface metal, such as zinc, aluminum or other substances in the pressure vessel.