Corrosion Protectors Extendthe service life of the metal structure, as well as its technical and physical properties during operation. Despite the variety of methods for ensuring anti-corrosion action, it is possible to completely protect objects from rust damage only in rare cases.
Эффективность такой защиты зависит не только от quality of the tread technology, but also on the conditions of its application. In particular, in order to preserve the metal structure of pipelines, electrochemical corrosion protection based on cathode performance demonstrates its best properties. Preventing the formation of rust on such communications is, of course, not the only field of application of this technology, but from the combination of characteristics this direction can be considered as the most relevant for electrochemical protection.
General information about electrochemical protection
Protecting metals from rust byElectrochemical effects are based on the dependence of the electrode potential of the material on the speed of the corrosion process. Metal structures should be operated in the range of potentials where their anodic dissolution is below the permissible limit. The latter, by the way, is determined by the technical documentation for the operation of the facility.
In practice, electrochemical corrosion protectioninvolves connecting to the finished product a source of direct current. The electric field on the surface and in the structure of the protected object forms the polarization of the electrodes, through which the process of corrosion damage is controlled. In essence, the anodic zones on the metal structure become cathodic, which allows to displace negative processes, ensuring the safety of the structure of the target object.
The principle of cathodic protection
There is cathodic and anodic protection.electrochemical type. The first concept, which is used to protect pipelines, gained the most popularity. According to the general principle, when this method is implemented, a current with a negative pole from an external source is supplied to the object. In particular, this way a steel or copper pipe can be protected, as a result of which polarization of the cathode sections will occur with the transition of their potentials to the anode state. As a result, the corrosive activity of the protected structure will be reduced to almost zero.
При этом и катодная защита может иметь разные execution options. The above-described polarization technique from an external source is widely practiced, but the method of electrolyte deaeration with a decrease in the rate of cathodic processes, as well as the creation of a sacrificial barrier, is also effective.
It has been noted more than once that the principle of cathodeprotection is implemented by an external power source. Actually, his work is the main function of anti-corrosion protection. These tasks are performed by special stations, which, as a rule, are included in the general infrastructure of pipeline maintenance.
Stations of cathodic corrosion protection
Главная функция катодной станции заключается в stable current supply of the target metal object in accordance with the method of cathodic polarization. Such equipment is used in the infrastructure of underground gas and oil pipelines, in water supply pipes, heat networks, etc.
There are many varieties of such sources, while the most common cathodic protection device provides for the composition of:
- current transducer equipment;
- wires for connection to the protected object;
- anode earthing.
При этом существует разделение станций на inverter and transformer. There are other classifications, but they are focused on the segmentation of installations or on the scope of application, or on the technical characteristics and parameters of input data. The basic principles of operation are most clearly illustrated by the designated two types of cathode stations.
Cathodic Protection Transformers
Immediately it should be noted that this type of stationsis outdated. In his turn just come inverter counterparts, which have both advantages and disadvantages. One way or another, transformer models are used even at new points of electrochemical protection.
As the basis of such objects is used50 Hz low-frequency transformer and thyristor converter. The simplest devices are used for the thyristor control system, among which are the phase-pulse power controllers. A more responsible approach to solving control problems involves the use of controllers with broad functionality.
Modern cathodic corrosion protectionpipelines with such equipment allows you to adjust the parameters of the output current, voltage indicators, as well as equalize the protective potentials. As for the shortcomings of transformer equipment, they are reduced to a high degree of current ripple at the output with a low power factor. This defect is explained not by a sinusoidal current form.
Solve the problem with the pulsation to a certain extent.allows the introduction of a low-frequency choke into the system, but its dimensions correspond to the size of the transformer itself, which does not always make such an addition possible.
Inverter station cathodic protection
Installations of invertor type are based onpulse high frequency converters. One of the main advantages of using stations of this type is high efficiency, reaching 95%. For comparison, in transformer installations, this figure reaches an average of 80%.
Иногда на первый план выходят и другие dignity. For example, the small dimensions of inverter stations expand the possibilities for their use in difficult areas. There are financial advantages, which are confirmed by the practice of using such equipment. So, the inverter cathodic protection against corrosion of pipelines quickly pays for itself and requires minimal investment in technical maintenance. However, these qualities are clearly noticeable only when compared with transformer installations, but today more effective new means of providing current for pipelines appear.
Cathode Station Constructions
Such equipment is presented in the market in differentenclosures, shapes and dimensions. Of course, the practice of individual design of such systems is widespread, which allows not only to obtain an optimal design for specific needs, but also to provide the necessary operational parameters.
Strict calculation of station characteristics allowsfurther optimize the cost of its installation, transportation and storage. For example, cathode corrosion protection of pipelines on an inverter basis with a mass of 10–15 kg and a power of 1.2 kW is quite suitable for small objects. Equipment with such characteristics can also be serviced by a passenger car, but for large-scale projects, more massive and heavy stations can be used, requiring the connection of trucks, a lifting crane, and teams of installers.
Protective functionality
Particular attention in the development of cathode stationsgiven the protection of the equipment itself. To this end, systems are integrated that allow stations to be protected from short circuits and load breaks. In the first case, special fuses are used to handle the emergency operation of the plants.
As for surges and voltage breaks,the cathodic protection station is unlikely to be seriously affected by them, but there may be a danger of electric shock. For example, if in normal mode the equipment is operated with a small voltage, then after a break, a jump in indicators can lead to 120 V.
Other types of electrochemical protection
In addition to cathodic protection, technology is also practiced.electrical drainage; and shedding methods to prevent corrosion. The most promising direction is considered to be a special protection from the formation of corrosion. In this case, the active elements are also connected to the target object, which ensure the transformation of the surface with the cathodes by means of current. For example, a steel pipe in a gas pipeline can be protected by zinc or aluminum cylinders.
Conclusion
Electrochemical protection methods can not be attributed tonew and, especially, innovative. The effectiveness of the application of such techniques in the fight against rusting processes has been mastered long ago. However, the wide distribution of this method is hampered by one serious drawback. The fact is that cathodic corrosion protection of pipelines inevitably produces so-called stray currents. They are not hazardous to the target structure, but can have a negative effect on nearby objects. In particular, the stray current contributes to the development of the same corrosion on the metal surface of adjacent pipes.
