Any metal products are easily destroyed under the influence of certain external factors, most often humidity. To prevent such phenomena, tread corrosion protection is used. Its task is to reduce the potential of the base material and thereby protect it from corrosion.
The essence of the procedure
Protective protection is based on a substance such as an inhibitor. This is a metal having increased electronegative qualities. When exposed to air, the tread dissolves. As a result, the base material is retained even if it is strongly affected by corrosion.
Various types of corrosion are easily defeated if cathodic electrochemical methods are used, which include tread protection. Such a procedure is an ideal solution when an enterprise does not have financial capabilities or technological potential in order to provide full protection against corrosion processes.
Main advantages
The tread protection of metals against corrosion is a good way to protect any metal surfaces. Its use is advisable in several cases:
- When an enterprise does not have enough production capacity to use more energy-consuming techniques.
- When you need to protect small-sized structures.
- If protection is required for metal products and objects whose surfaces are coated with insulating materials.
To achieve maximum efficiency, it is advisable to use tread protection in an electrolytic environment.
When is protection required?
Corrosion occurs on any metal surface in a wide variety of fields - from the oil and gas industry to shipbuilding. Tread corrosion protection is widely used in the painting of tanker hulls. These vessels are constantly exposed to water, and special painting does not always cope with the prevention of moisture reactions with a metal surface. The use of protectors is a simple and effective solution to the problem, especially if the vessels will be in operation for a long time.
Most metal structures are made of steel, so it is advisable to use protectors with a negative electrode potential. The main for the production of protectors are three metals - zinc, magnesium, aluminum. Due to the large potential difference between these metals and steel, the radius of the protective action becomes wider, and any kind of corrosion is easily eliminated.
What metals are used?
The protective system is built on the basis of various alloys, depending on the specific use of the protectors, for example, the environment in which it will be used. Tread protection against corrosion is most often required by iron and steel products, but it is also required by zinc, aluminum, cadmium or magnesium surfaces. A feature of tread protection is the use of galvanic anodes, which protect the pipes from soil corrosion. The calculation of such installations is carried out taking into account a number of parameters:
- current strength in the tread;
- indicators of its resistance;
- degree of protection required for 1 km of pipe;
- the number of protectors for the same segment;
- the distance that exists between the elements of the protective system.
Pros and cons of various protectors
On the basis of protectors, the protection of building structures against corrosion and various types of pipelines (distribution, trunk, and field) are built. At the same time, they must be used competently:
- the use of aluminum protectors is advisable in order to protect structures and structures in sea water and offshore;
- Magnesium is suitable for use in low conductivity environments where aluminum and zinc protectors show low efficiency. But they cannot be used if it is necessary to protect the internal surfaces of tankers, tanks, oil sumps, since magnesium protectors are characterized by increased explosion and fire hazard. Ideally, projectors based on this element should be used for external protection of structures that are used in a fresh environment;
- zinc protectors are completely safe, therefore they can be used at any objects, even if they have a high level of fire hazard.
If the coating is paintwork
Very often it is required to protect the oil or gas pipeline from corrosion, taking into account the paintwork. Combining it with a tread is a passive way to protect structures from corrosion. Moreover, the effectiveness of such an event is not so high, but the following is achieved:
- defects on coatings of structures made of metals and pipelines are leveled, for example, peeling, cracking;
- the consumption of tread materials is reduced, while the protection itself is more durable;
- protective current is evenly distributed on the metal surface of the product or object.
Tread corrosion protection in combination with paints and varnishes - this is the ability to distribute the protective current precisely on those surfaces that require maximum attention.
About pipeline protection
During operation, metal pipes inside and out are exposed to corrosion. Plaque appears due to the fact that aggressive substances flow through the pipes, which react with the materials. The internal state of metal products is affected by a high level of soil moisture. If the quality protection of building structures against corrosion is not thought out, the following will happen:
- the pipeline will begin to collapse from the inside;
- more frequent preventive examinations of highways will be required;
- more frequent repairs will be required, which will affect additional expenses;
- it will be necessary to completely or partially stop the oil refining or other other industrial complex.
There are several ways to protect pipelines - passive, active. Also, as a means of protection, a decrease in the aggressiveness of the environment can act. In order for the protection to be comprehensive, the type of pipeline, the method of its installation and its interaction with the environment are taken into account.
Passive and active defense methods
All the main ways to protect pipelines from corrosion come down to a number of works. If we talk about passive methods, they are expressed in the following:
- a special way of laying, when the resistance to corrosion is thought out even at the stage of installation of the pipeline. To do this, an air gap is left between the ground and the pipe, due to which neither groundwater, nor salt, nor alkali will get into the pipeline;
- applying special coatings to pipes that will protect the surface from soil influences;
- processing with special chemistry, for example, phosphates, forming a protective film on the surface.
The protection scheme based on active methods involves the use of electric current and electrochemical reactions of ion exchange:
- electric drainage protection to combat stray currents;
- anode protection, which slows down the process of metal destruction;
- cathodic protection, when direct current increases the resistance of metals.
Arguments for tread protection
As you can see, there are many ways to improve the protective characteristics of pipelines and other metal products. But they all require a waste of electric current. Tread protection against corrosion of pipelines is a more profitable solution, since all oxide processes are stopped by simply applying alloys of other materials to the surface of pipes made of metals. The following factors speak in favor of this method:
- profitability and simplicity of the process due to the lack of a direct current source and the use of magnesium, zinc or aluminum alloys;
- the possibility of using single or group installations, while the tread protection scheme is thought out taking into account the features of the projected or already constructed object;
- the possibility of application on any soil and in the conditions of the seas / oceans, where it is expensive or impossible to use external current sources
Tread protection can be used to increase the corrosion resistance of various tanks, ship hulls, tanks, which are used in extreme conditions.