1 The technical problems involved in the monitoring, control and protection of corrosion are extensive. Only in terms of corrosion control and protection, there are many technical means to choose from, for example, cathode and anode protection, material selection, corrosion inhibitors, and internal and external coating technologies. Corrosion monitoring is a quantification method. It uses a variety of techniques to determine the corrosivity of the environment and the rate of metal loss. It can be used to evaluate the effectiveness of corrosion control and protection technology, which in turn can provide a basis for the design of these aspects.
Although the economic benefits of corrosion detection and monitoring technology for industrial equipment are difficult to assess specifically due to various reasons, it is generally believed that successful corrosion monitoring on industrial equipment will bring tens or hundreds of times the cost of investment. High economic efficiency (including increasing profits and saving additional expenses).
With the development of integration of production devices, the accidental damage of a simple unit will incur huge economic losses. At present, people’s concern for personal safety in the industry is increasing, and awareness of environmental issues has generally increased. By carefully implementing corrosion monitoring, the reliability of the above two aspects can be increased, and the benefits derived from improving the reliability are also considerable.
Many important issues of corrosion and protection have been gradually recognized and put forward in the process of industrial modernization. Considering the commonly accepted figure that corrosion losses generally account for 4 per cent of the national economy, industrialized countries have a high total output value and the absolute number of losses is large. Therefore, the corrosion problems encountered by industrialized countries tend to be older and more . In industrial enterprises in industrialized countries, corrosion monitoring is considered to be an important guarantee for achieving civilized production, and a series of industrial on-site corrosion monitoring devices have been developed.
2 Development of Corrosion Monitoring Technology Corrosion monitoring technology is developed from laboratory corrosion test methods and equipment non-destructive testing techniques. Its purpose is to reveal the corrosion process and to understand the application and control effects of corrosion control. Most modern corrosion monitoring practices come from industries such as chemistry, petrochemistry, oil refining, and power. In these industries, corrosion behavior is often sensitive to many variables and changes drastically with changes in conditions. Therefore, the pattern of corrosion behavior It may be complicated. The classic corrosion monitoring method is mainly to install and remove the hanging pieces during the stop and maintenance, and to inspect the inside of the equipment during the stop. This mode of operation determines that the test cycle depends on the maintenance cycle. Process and equipment conditions tend to change during this cycle. In particular, some factors that have an important influence on the corrosion process, the corrosion rate and morphology may also be greatly changed The result obtained is only the sum of the corrosion generated throughout the test cycle. This often leads to an inability to interpret the test results, and sometimes completely different test results may be obtained on almost the same device.
In order to make the test time independent of the inspection cycle, a bypass test device and a test heat exchanger were used. Afterwards, it was realized that the sample was loaded or removed during operation of the device. If you want to systematically and comprehensively understand the corrosion behavior, the most important thing is to use a technology that can respond quickly. With the development of modern electronic technology, the principle of corrosion monitoring has been applied to more complex occasions, which has greatly promoted the development of industrial corrosion monitoring technology. It can overcome some of the limitations due to technology simplification and online applications.
The technologies currently used for real-time monitoring of industrial sites can be roughly divided into two categories. One category is the long history of research and has formed more mature technological methods. These include: resistance (ER), linear polarization (LPR), potentiometry, and ultrasonic thickness measurements. These methods also have some problems: ultrasonic thickness measurement and resistance method can repeatedly measure the running equipment, but it is difficult to obtain sufficient sensitivity to track and record the change of corrosion speed; linear polarization method responds quickly to changes in corrosion, energy Instantaneous corrosion rate is obtained, but it is not suitable for application in poor conductivity media. When the device surface has a dense oxide film or passivation film, even if there is accumulated corrosion products, false capacitance will be generated, causing great errors. Even impossible to measure; potentiometry has been used for many years in cathodic protection system monitoring and is used to determine the conditions under which local corrosion occurs, but it does not reflect the corrosion rate.
In recent years, a new type of rapidly growing corrosion monitoring method has emerged.
This includes:
AC impedance technology has great reliability for high resistance electrolytes and a wide range of media conditions. It takes a long time to measure the AC impedance over a wide frequency range, which makes it difficult to monitor the corrosion rate in real time and is not suitable for actual on-site corrosion monitoring.
In order to overcome this shortcoming, people have designed and manufactured an automatic AC corrosion monitor by appropriately selecting two frequencies, monitoring the corrosion rate of the metal, and electrochemical noise technology including electrochemical potential noise ( EPN) and electrochemical current noise (ECN), which reflect the slight fluctuation of corrosion potential or galvanic current due to corrosion; the application of these technologies in industrial production has begun exploratory research; Thin Layer Activation Technology (TLA) The advantage of this method is that the total metal loss can be measured directly from the components and the sensitivity is high. There is also Field Image Technology (FSM), which is used for real-time on-site monitoring of submarine oil pipelines. This technology can also perform corrosion monitoring on inaccessible parts, such as monitoring of dangerous area cracks in nuclear power plant equipment with radiation hazards. In addition, emerging constant-power technologies and inductor impedance methods have made new breakthroughs in corrosion monitoring in terms of speed, accuracy, and application range, but most of them have just surpassed the scope of laboratory research and are entering the real-time on-site corrosion monitoring stage. No mature technology has yet been formed.
While discussing the development direction of corrosion monitoring technology, we must mention the innovation brought by computer technology and the impact on future corrosion research. In this regard, the United States EGG Corporation, Gamry Corporation, the United Kingdom Solartron Corporation, Germany's ZANHER Corporation, the Netherlands EcoChemie and other companies dedicated to computerized experimental devices (such as potentiostats, frequency response analyzers, etc.). Computers can use feedback to experiment, change and adjust experimental parameters to achieve pre-defined goals, so that corrosion monitoring research to a new level, monitoring technology began to enter the level of intelligence.
3 Intelligent Corrosion Monitoring Instruments Intelligent corrosion testing instruments have developed rapidly. Many commercial microprocessor-based corrosion monitoring systems have emerged. Intelligent instruments are an integrated implementation of microprocessors and instruments. Can test, output detection signal, but also can store, extract, process, and process the monitoring signal to meet the needs of dynamic, fast, multi-parameter, real-time measurement and data processing. The intelligent instrument has become 20 A major direction of corrosion monitor development since the 1980s. For different monitoring objects, configure certain hardware and corresponding software for corrosion monitoring. The instrument also has internal data bus, control bus, and address bus. The sensor converts the measured corrosion information into electrical signals through A/D and D/. A conversion interface, the microprocessor is responsible for test control, data acquisition, calculation of corrosion data and print results.
Among the numerous intelligent corrosion monitor products at home and abroad, a large part are linear polarization type and resistance corrosion probes.
Typical products of linear polarization instruments are: the United States Magrator Corporation Corrator series, Petroliet's PAIR-Meter series, British Waverley's CM471, French Tacussel Elec-tronique's Corrovit, Italian AtelSRL's Corrosimtro series and Czech's VPZPraha-Bechovice The production of Polarotron and so on. Resistance corrosion probes include Nalfoc products from the United Kingdom and Corrosome-ter from Magna USA.
Although the economic benefits of corrosion detection and monitoring technology for industrial equipment are difficult to assess specifically due to various reasons, it is generally believed that successful corrosion monitoring on industrial equipment will bring tens or hundreds of times the cost of investment. High economic efficiency (including increasing profits and saving additional expenses).
With the development of integration of production devices, the accidental damage of a simple unit will incur huge economic losses. At present, people’s concern for personal safety in the industry is increasing, and awareness of environmental issues has generally increased. By carefully implementing corrosion monitoring, the reliability of the above two aspects can be increased, and the benefits derived from improving the reliability are also considerable.
Many important issues of corrosion and protection have been gradually recognized and put forward in the process of industrial modernization. Considering the commonly accepted figure that corrosion losses generally account for 4 per cent of the national economy, industrialized countries have a high total output value and the absolute number of losses is large. Therefore, the corrosion problems encountered by industrialized countries tend to be older and more . In industrial enterprises in industrialized countries, corrosion monitoring is considered to be an important guarantee for achieving civilized production, and a series of industrial on-site corrosion monitoring devices have been developed.
2 Development of Corrosion Monitoring Technology Corrosion monitoring technology is developed from laboratory corrosion test methods and equipment non-destructive testing techniques. Its purpose is to reveal the corrosion process and to understand the application and control effects of corrosion control. Most modern corrosion monitoring practices come from industries such as chemistry, petrochemistry, oil refining, and power. In these industries, corrosion behavior is often sensitive to many variables and changes drastically with changes in conditions. Therefore, the pattern of corrosion behavior It may be complicated. The classic corrosion monitoring method is mainly to install and remove the hanging pieces during the stop and maintenance, and to inspect the inside of the equipment during the stop. This mode of operation determines that the test cycle depends on the maintenance cycle. Process and equipment conditions tend to change during this cycle. In particular, some factors that have an important influence on the corrosion process, the corrosion rate and morphology may also be greatly changed The result obtained is only the sum of the corrosion generated throughout the test cycle. This often leads to an inability to interpret the test results, and sometimes completely different test results may be obtained on almost the same device.
In order to make the test time independent of the inspection cycle, a bypass test device and a test heat exchanger were used. Afterwards, it was realized that the sample was loaded or removed during operation of the device. If you want to systematically and comprehensively understand the corrosion behavior, the most important thing is to use a technology that can respond quickly. With the development of modern electronic technology, the principle of corrosion monitoring has been applied to more complex occasions, which has greatly promoted the development of industrial corrosion monitoring technology. It can overcome some of the limitations due to technology simplification and online applications.
The technologies currently used for real-time monitoring of industrial sites can be roughly divided into two categories. One category is the long history of research and has formed more mature technological methods. These include: resistance (ER), linear polarization (LPR), potentiometry, and ultrasonic thickness measurements. These methods also have some problems: ultrasonic thickness measurement and resistance method can repeatedly measure the running equipment, but it is difficult to obtain sufficient sensitivity to track and record the change of corrosion speed; linear polarization method responds quickly to changes in corrosion, energy Instantaneous corrosion rate is obtained, but it is not suitable for application in poor conductivity media. When the device surface has a dense oxide film or passivation film, even if there is accumulated corrosion products, false capacitance will be generated, causing great errors. Even impossible to measure; potentiometry has been used for many years in cathodic protection system monitoring and is used to determine the conditions under which local corrosion occurs, but it does not reflect the corrosion rate.
In recent years, a new type of rapidly growing corrosion monitoring method has emerged.
This includes:
AC impedance technology has great reliability for high resistance electrolytes and a wide range of media conditions. It takes a long time to measure the AC impedance over a wide frequency range, which makes it difficult to monitor the corrosion rate in real time and is not suitable for actual on-site corrosion monitoring.
In order to overcome this shortcoming, people have designed and manufactured an automatic AC corrosion monitor by appropriately selecting two frequencies, monitoring the corrosion rate of the metal, and electrochemical noise technology including electrochemical potential noise ( EPN) and electrochemical current noise (ECN), which reflect the slight fluctuation of corrosion potential or galvanic current due to corrosion; the application of these technologies in industrial production has begun exploratory research; Thin Layer Activation Technology (TLA) The advantage of this method is that the total metal loss can be measured directly from the components and the sensitivity is high. There is also Field Image Technology (FSM), which is used for real-time on-site monitoring of submarine oil pipelines. This technology can also perform corrosion monitoring on inaccessible parts, such as monitoring of dangerous area cracks in nuclear power plant equipment with radiation hazards. In addition, emerging constant-power technologies and inductor impedance methods have made new breakthroughs in corrosion monitoring in terms of speed, accuracy, and application range, but most of them have just surpassed the scope of laboratory research and are entering the real-time on-site corrosion monitoring stage. No mature technology has yet been formed.
While discussing the development direction of corrosion monitoring technology, we must mention the innovation brought by computer technology and the impact on future corrosion research. In this regard, the United States EGG Corporation, Gamry Corporation, the United Kingdom Solartron Corporation, Germany's ZANHER Corporation, the Netherlands EcoChemie and other companies dedicated to computerized experimental devices (such as potentiostats, frequency response analyzers, etc.). Computers can use feedback to experiment, change and adjust experimental parameters to achieve pre-defined goals, so that corrosion monitoring research to a new level, monitoring technology began to enter the level of intelligence.
3 Intelligent Corrosion Monitoring Instruments Intelligent corrosion testing instruments have developed rapidly. Many commercial microprocessor-based corrosion monitoring systems have emerged. Intelligent instruments are an integrated implementation of microprocessors and instruments. Can test, output detection signal, but also can store, extract, process, and process the monitoring signal to meet the needs of dynamic, fast, multi-parameter, real-time measurement and data processing. The intelligent instrument has become 20 A major direction of corrosion monitor development since the 1980s. For different monitoring objects, configure certain hardware and corresponding software for corrosion monitoring. The instrument also has internal data bus, control bus, and address bus. The sensor converts the measured corrosion information into electrical signals through A/D and D/. A conversion interface, the microprocessor is responsible for test control, data acquisition, calculation of corrosion data and print results.
Among the numerous intelligent corrosion monitor products at home and abroad, a large part are linear polarization type and resistance corrosion probes.
Typical products of linear polarization instruments are: the United States Magrator Corporation Corrator series, Petroliet's PAIR-Meter series, British Waverley's CM471, French Tacussel Elec-tronique's Corrovit, Italian AtelSRL's Corrosimtro series and Czech's VPZPraha-Bechovice The production of Polarotron and so on. Resistance corrosion probes include Nalfoc products from the United Kingdom and Corrosome-ter from Magna USA.
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