An important feature of modern chemical production is the large-scale and highly automated production equipment. Automation is a basic condition and important guarantee for the safe operation, stable operation, and efficiency improvement of production equipment. However, with the development of production and the improvement of automatic control levels, the corrosion problem of chemical instruments has become increasingly prominent, and anti-corrosion of chemical instruments has increasingly become an important issue that the instrument industry urgently needs to solve. Chemical instruments are essential monitoring equipment. On the one hand, chemical instruments can maintain the stable operation of chemical production lines; on the other hand, they also play a role in protecting life and property safety. For on-site instruments, which are exposed to the outside for a long time, exposed to sun and rain, it is easy for instruments to fail. Therefore, we need to do a good job in anti-corrosion of instruments. Strengthening the management and maintenance of instruments can not only improve the accuracy of instruments but also extend their service life. 01. Analysis of corrosion causes of chemical machinery and equipment In the actual use of chemical machinery and equipment, they will be affected by many factors, which affect the operation efficiency and quality of the equipment and restrict the production efficiency of chemical enterprises. The anti-corrosion of chemical equipment mainly improves the anti-corrosion ability of mechanical equipment through relevant processes, so that mechanical equipment can continue to function in chemical environments full of strong acids, strong alkalis, etc., improve the safety factor, and avoid potential safety hazards. Analyze the corrosion causes affecting chemical machinery and equipment to improve their anti-corrosion ability. 1. Internal corrosion causes The internal parts of mechanical equipment are corroded by chemical materials, which affects the quality of mechanical equipment. In actual chemical production, due to the active nature of metal materials, mechanical equipment will come into direct contact with oxygen, strong acids, strong alkalis, etc., leading to corrosion. Moreover, there are differences in the anti-corrosion ability inside the materials used in mechanical equipment, resulting in differences in the internal anti-corrosion ability of mechanical equipment. This leads to different degrees of corrosion of components in the same environment, affecting the operation quality of mechanical equipment. In addition, the maintenance of the surface of mechanical equipment also affects corrosion, and the rougher the surface of mechanical equipment, the more susceptible it is to corrosion. 2. External corrosion causes During the actual use of mechanical equipment, they will be corroded by the external environment. In chemical production, factors such as oxygen, acids, and alkalis come into direct contact with the outside of mechanical equipment, and chemical equipment is corroded by acids, alkalis, and oxygen. Furthermore, in the chemical production environment, a large amount of chemical raw materials will accumulate, and these raw materials will come into contact with mechanical equipment, leading to corrosion of mechanical equipment by the external environment and affecting the operation quality of the equipment. External environments such as high temperature and high pressure will affect the operation efficiency of mechanical equipment, causing corrosion on the outside of the equipment. If both the inside and outside of the mechanical equipment are corroded, it is mainly because the equipment is in some solutions of chemical enterprises for a long time, so that all parts of the mechanical equipment are corroded. This affects all parts of the mechanical equipment, reduces the safety factor and service quality of the equipment, and in severe cases, causes resource waste, affecting the cost and production efficiency of chemical enterprises. 02. Main corrosion types of chemical instruments Corrosion occurs because metals have physical and chemical reactions with moisture and gases in the external environment, resulting in changes in the surface and internal properties of metals, and damage to the functional structure of parts composed of metal materials or other components. In the petrochemical industry, chemical instruments and their components are prone to physical, chemical, and electrochemical reactions with the external contact environment, causing damage to chemical instruments and their components. Transmitters are commonly used as front-end collection and detection devices in industrial sites. Transmitters are composed of sensor diaphragms and connecting wires, and these components are made of precious metals to improve the detection accuracy and sensitivity of the equipment. These devices are exposed to the harsh environment of industrial sites, causing corrosion. Common corrosion types include: 1. Physical corrosion Physical corrosion of chemical instruments is caused by the damage of metal materials by external mechanical forces and the physical dissolution of metal materials. 2. Chemical corrosion The metal materials of instruments are prone to redox reactions with gases in the external contact environment, and non-electrolyte solutions come into contact with metal materials to produce oxidative corrosion, which are all chemical corrosion of chemical instruments. Toxic gas chlorine produced in chemical plants undergoes a redox reaction with iron in instrument components to form ferrous chloride, causing instrument corrosion. 3. Electrochemical corrosion Electrochemical corrosion is the most common type of corrosion in chemical instruments. In chemical environments, there are common corrosive substances such as strong acids and strong alkalis. When the metal materials of chemical instruments come into contact with electrolyte solutions, a galvanic cell reaction occurs, and active metal materials with strong reducibility lose electrons and are oxidized. Iron and steel materials are more susceptible to corrosion in humid air because the surface of iron and steel reacts to form electrolytes in humid air, and the electrolyte solution forms a galvanic cell device with iron and carbon in the steel, and iron elements lose electrons and are oxidized. The damage of many metal substances is caused by electrochemical corrosion. Electrochemical corrosion can corrode the surface and internal parts of instruments in a short time, and the precipitates caused by corrosion will affect the precision and accuracy of instruments. 03. Common anti-corrosion methods for chemical instruments In the actual production process, the existence of corrosion causes frequent instrument failures. Enterprises often replace instruments to ensure the normal operation of production equipment, thereby increasing enterprise operation and maintenance costs. Common anti-corrosion methods widely used in the chemical industry include gas isolation, liquid isolation, and diaphragm isolation. 1. Gas isolation method The principle of gas isolation is to fill the pressure guiding pipe between the detection point and the instrument detection element with air to prevent the detected pressure medium from directly contacting the instrument, thus protecting the instrument from damage by high-pressure measured media. The gas isolation method is also called gas injection protection method, which is used when a pressure transmitter is used to measure low pressure or absolute pressure. The pressure change at the detection point is transmitted to the instrument transmitter through the air in the pressure guiding pipe, and the result is obtained through the detection of the instrument's sensitive element. 2. Liquid isolation method When measuring media such as hydrogen chloride gas, nitrogen oxide gas, and chlorine gas, perfluorotributylamine or other isolation liquids are filled in the isolation tank to isolate the corrosive medium from the metal parts of the detection instrument. The liquid isolation method has some disadvantages. For example, adding a liquid seal will introduce a liquid seal medium, and the measured medium may react with the liquid seal medium, resulting in new corrosion problems and reducing the isolation effect. At the same time, the isolation liquids on the market are generally expensive, the filling method is troublesome, and the anti-corrosion effect is not good, so the liquid isolation method is not widely used in practical applications. 3. Diaphragm isolation Due to the characteristics of polytetrafluoroethylene, such as high lubrication, resistance to high and low temperatures, resistance to climate aging, corrosion resistance, non-adhesion, low tension, and low friction coefficient, it is resistant to most chemical solvents and drugs. Therefore, the anti-corrosion isolation diaphragm of chemical instruments is made of polytetrafluoroethylene. The specific application method is to adhere or spray FEP (fluorinated ethylene propylene) or polytetrafluoroethylene diaphragms on the bellows of pressure transmitters or the bourdon tubes of pressure gauges, so as to isolate the corrosive medium from the sensing elements to achieve anti-corrosion purposes. Applications show that FEP diaphragms can prevent corrosion from common corrosive media, ensure the accuracy of instrument measurement during the measurement process, and greatly extend the service life of detection instruments. In addition, FEP diaphragms are relatively inexpensive. The method of anti-corrosion using diaphragm isolation can solve the corrosion problem on the one hand and reduce production costs on the other hand. 04. Treatment methods for corrosion problems of chemical instruments 1. Select materials with strong corrosion resistance The root cause of corrosion problems in chemical instruments is their own material issues. Nowadays, chemical instruments are usually made of metal materials, which are prone to corrosion. When in contact with chemical media and high-temperature and high-pressure substances, the probability of chemical reactions is higher, and the reactions are more intense, aggravating the degree of corrosion. Therefore, in order to fundamentally solve the corrosion problem of chemical instruments and extend their service life, we should start with the preparation materials of chemical instruments, select appropriate anti-corrosion materials to replace traditional metal materials, so as to reduce the corrosion damage caused by chemical production to chemical instruments and save maintenance and replacement costs. The material selection of chemical instruments should try to improve the anti-corrosion performance of the materials. When in contact with chemical media and high-temperature and high-pressure environments, they can maintain good stability without chemical, electrochemical, or physical reactions, improve corrosion resistance, and reduce corrosion problems. It is true that using some materials with strong corrosion resistance to make chemical instruments can effectively play an anti-corrosion role. However, the selection of materials for chemical instruments cannot only consider corrosion resistance. The selected materials must have good performance and be able to be based on the working environment of the instrument, the cost of the instrument, and the corresponding supply situation, etc. The performance of materials is very important, and their mechanical and physical properties will have a decisive impact on the working conditions of the instrument. This is mainly because the chemical composition and substance content they contain are different. Another point is to carefully analyze the working environment of chemical instruments, especially the humidity in the working environment and the content of corrosive substances, etc. These will affect the service life and daily work efficiency of chemical instruments, so comprehensive consideration must be given. 2. Apply protective layers Forming a protective layer on instrument parts or components is a very common anti-corrosion method in industry. According to the different materials and forming principles of the protective layer, it can be divided into the following three types: Metal protective layers, including spraying, electroplating, hot dipping, carburizing, etc. Non-metallic protective layers, such as paint, acid-resistant cement, rubber, plastic, enamel, etc.; Among them, painting anti-corrosion paint on chemical instruments costs relatively low, and the painting of anti-corrosion paint can be repeated. Regular touch-up and repainting can keep chemical instruments in a good anti-corrosion environment for a long time. Therefore, even though painting anti-corrosion paint has certain limitations in use, it is often used in the anti-corrosion treatment of chemical instruments, and is very effective, reliable, and the treatment process is very simple. When painting anti-corrosion paint on chemical instruments, it is necessary to strictly control the selection and painting operation of anti-corrosion paint, as far as possible to reduce the impact of the painted anti-corrosion paint on the normal use of chemical instruments, affecting their performance, or causing certain interference to chemical production. Non-metallic protective films, which are formed by chemical treatment on the metal surface to generate oxide films, phosphate films and other protective films. 3. Strictly control the number of microorganisms Chemical instruments will be corroded by microorganisms during use, and this kind of corrosion can be controlled through necessary prevention and control measures. The specific operation is to strictly control the number of microorganisms to inhibit their corrosion of chemical instruments. Chemical instrument maintenance personnel need to regularly measure the number of标志性 microorganisms such as heterotrophic bacteria and bacteria. When abnormal numbers of microorganisms are found, they should promptly carry out drug treatment to kill the microorganisms, and scientifically adjust the dosage and types of drugs according to the type and number of bacteria. However, it should not affect the normal progress of chemical production, and a feasible method must be formulated through strict theoretical verification and scientific experiments to reduce the corrosion damage of microorganisms to chemical instruments. 4. Strengthen the use management of chemical instruments The use of chemical instruments must be in strict accordance with the corresponding operating specifications, which can effectively reduce the probability of corrosion problems. The surface corrosion of chemical instruments can be repaired and remedied, with less impact, and can be put back into use by replacing the shell. However, if internal corrosion occurs in chemical instruments, it will cause more serious consequences, damaging various electronic components and chips inside the chemical instruments. In this case, the normal use can only be restored by replacing the entire instrument, which costs a lot. Therefore, it is necessary to strengthen the use management of chemical instruments and make effective prevention and disposal decisions for common corrosion problems of chemical instruments in chemical production. 5. Carry out isolation work The service environment of chemical instruments is very complex. Therefore, no matter what kind of anti-corrosion materials are selected, some chemical, physical, and electrochemical reactions will inevitably occur during actual use, and instrument corrosion problems cannot be completely eliminated. Therefore, in order to extend the service life of chemical instruments as much as possible, it is necessary to actively carry out isolation work according to the actual working environment and performance characteristics of chemical instruments to reduce the probability of corrosion. First, chemical enterprises can use radioactive, ultrasonic, light radiation and other monitoring instruments, which can completely avoid the instruments being corroded and damaged by media, but the cost is high, and subsequent maintenance is relatively complicated. Secondly, the use of isolation devices, isolation diaphragms, isolation liquids and other isolation measures can isolate the instrument detection part from the medium to achieve anti-corrosion effects. Isolation anti-corrosion is an effective method for instrument anti-corrosion. According to different actual working conditions and the needs of measurement and control, we can take methods such as adding isolation liquid, blowing gas, and adding protective layers to effectively prevent or slow down instrument corrosion. In summary, with the rapid development of the economy, people's demand for chemical products continues to increase, which requires enterprises to improve production efficiency. The application of automated instrument equipment has greatly improved enterprise production efficiency, but enterprises should focus on anti-corrosion treatment of instruments to solve instrument corrosion problems and improve enterprise economic benefits. Article sources: Chemical 707, Gongke, Process Industry