How to protect pipes from corrosion. Protection of metal pipes located in the ground. Painting of steel parts

Almost any system internal infrastructure and life support residential buildings, municipal and commercial buildings or industrial facilities, by and large, is a developed network of pipelines connecting various objects of the system to each other in a certain order.

In most cases, for example, when arranging a gas pipeline, hot and cold water supply, fecal or cable and ventilation, underground, air or internal laying is used. metal pipes various diameters and sizes.

Depending on the operating mode and environmental conditions, metal pipes during operation can be subjected to prolonged exposure to various adverse factors. To solve this problem, a comprehensive protection of pipelines against corrosion was specially developed according to SNiP 2.03.11-85 "Protection building structures from corrosion."

Corrosion Control Methods

To help the reader understand how to maximize pipeline longevity, this article will look at some active and passive protection options. metal products included in the pipeline engineering communications.

Also there will be detailed instructions, which describes in detail the basic principles for the implementation of anti-corrosion protection for metal products intended for operation in aggressive conditions.

Classification of harmful factors

As mentioned above, the nature and degree of influence of external factors largely depends on specific conditions operation, such as the location of the pipe, the chemical composition of the soil, the average annual temperature and relative humidity environment, presence of direct current sources nearby, etc.

According to the mechanism of occurrence and the degree of destructive impact, all harmful factors can be conditionally divided into several types.

1. atmospheric corrosion occurs when iron interacts with water vapor, which is contained in the surrounding air, as well as as a result of direct contact with water during precipitation precipitation. During the course of a chemical reaction, iron oxide is formed, or, more simply, ordinary rust, which significantly reduces the strength of metal products, and over time can lead to their complete destruction.

1. Chemical corrosion occurs as a result of the interaction of iron with various active chemical compounds(acids, alkalis, etc.). At the same time, the flowing chemical reactions lead to the formation of other compounds (salts, oxides, etc.), which, like rust, gradually destroy the metal.
2. Electrochemical corrosion occurs when an iron product is in an electrolyte environment for a long time ( water solution salts of various concentrations). In this case, anode and cathode sections are formed on the metal surface, between which an electric current flows. As a result of electrochemical emission, iron particles are transferred from one area to another, which leads to the destruction of a metal product.
3. Impact of negative temperatures in cases where pipes are used to transport water, it leads to its freezing. Upon transition to a solid state of aggregation, it forms in water crystal cell, as a result of which its volume increases by 9%. Being in a closed space, water begins to put pressure on the walls of the pipe, which ultimately leads to their rupture.

Note! A significant difference in average annual and average daily temperatures leads to significant fluctuations in the total length of the pipeline, which are caused by linear thermal expansion of the material. To prevent rupture of pipes and damage load-bearing structures, after a certain distance on the line it is necessary to install thermal compensators.

Soil analysis

In order to choose the most effective method of protection, it is necessary to have accurate information about the nature of the environment and the specific operating conditions of the steel pipeline. In the case of laying internal or overhead line this information can be obtained on the basis of subjective observations, as well as on the basis of the average annual climatic regime for a given region.

In the case of laying an underground pipeline, the corrosion resistance and durability of the metal largely depend on the physical parameters and chemical composition soil, therefore, before digging a trench with your own hands, it is necessary to submit soil samples for analysis to a specialized laboratory.

The most important indicators that need to be clarified in the analysis process are the following soil qualities:

1. The chemical composition and concentration of salts of various metals in groundwater. The density of the electrolyte and the electrical permeability of the soil largely depend on this indicator.
2. Qualitative and quantitative indicators of soil acidity, which can cause both chemical oxidation and electrochemical corrosion metal.
3. Soil electrical resistance. The lower the electrical resistance value, the more susceptible the metal is to damage caused by electrochemical emission.

Advice! To obtain objective results of the analysis, soil samples must be taken from those soil layers in which the pipeline will pass.

Low temperature protection

In the case of underground or air, the most important condition for their uninterrupted operation is the protection of pipes from freezing and maintaining the water temperature at a level not lower than 0 ° C during the cold season.

To reduce the negative impact of the environmental temperature factor, the following technical solutions are used:

1. Laying an underground pipeline at a depth exceeding the maximum freezing depth of the soil for a given region.
2. Thermal insulation of air and underground lines with help various materials with low thermal conductivity (mineral wool, foam segments, foam sleeves).

1. Backfilling the pipeline trench bulk material with low thermal conductivity (expanded clay, coal slag).
2. Drainage of adjacent soil layers in order to reduce its thermal conductivity.
3. pad underground utilities in rigid closed boxes made of reinforced concrete, which provide the presence air gap between pipe and soil.

Most progressive method How to protect pipes from freezing is to use a special casing, consisting of a shell made of heat-insulating material, inside which an electric heating element is laid.

Note! The depth of soil freezing for each specific region, as well as the method of its calculation is regulated normative documents SNiP 2.02.01-83* "Foundations of buildings and structures" and SNiP 23-01-99* "Construction climatology".

External waterproofing coating

The most common way to combat metal corrosion is to apply a thin layer of durable waterproof protective material to its surface. The simplest example of an outdoor protective coating is the usual waterproof paint or enamel, such as protection gas pipe passing through the air is always done with weatherproof yellow enamel.

Underground water and gas pipelines are usually assembled from pipes that are pre-coated on the outside with a thick layer bituminous mastic and then wrapped in thick technical paper. Also high efficiency have coatings of composite or polymeric materials.

The metal elements of sewer underground communications are covered from the inside and outside with a thick layer of cement-sand mortar, which, after hardening, forms a uniform monolithic surface.

To choose on your own suitable material for outdoor coating, you need to know that for maximum protection it must have several qualities at the same time.

1. The paintwork after drying should have a continuous, uniform surface with a high mechanical strength and absolute resistance to water.
2. The protective film of the waterproofing material, with the specified properties, must be elastic and not collapse under the influence of high or low temperatures.
3. The starting material for coating should have good flowability, high hiding power, as well as good adhesion to the metal surface.
4. Another indicator of a quality insulating material is that it must be an absolute dielectric. This property provides reliable protection pipelines from stray currents, which increase the adverse effects of electrochemical corrosion.

Advice! Most effective solutions to isolate metal from the environment, it is customary to consider compositions based on bituminous resins, two-component polymer compositions, as well as rolled polymer materials self-adhesive.

Active and passive electrochemical protection

Underground engineering Communication more prone to corrosion than air and internal pipelines, because they are constantly in the electrolyte environment, which is a solution of salts contained in groundwater.

In order to minimize the destructive effect caused by the reaction of iron with a water-salt electrolyte solution, active and passive methods of electrochemical protection are used.

1. Active cathodic method consists in the directed movement of electrons in a constant circuit electric current. To carry it out, a pipeline is connected to the negative pole of the DC source, and an anode ground rod is connected to the positive pole, which is buried in the ground nearby. After applying voltage electrical circuit closes through the soil electrolyte, as a result of which free electrons begin to move from the ground rod to the pipeline. Thus, the ground electrode is gradually destroyed, and the released electrons, instead of the pipeline, react with the electrolyte.

1. Passive sacrificial protection of pipelines It consists in placing an electrode made of a more electronegative metal, such as zinc or magnesium, next to iron in the ground and electrically connecting them together through a controlled load. In the electrolyte environment, they form a galvanic couple, which during the reaction, as in the previous case, causes the movement of electrons from the zinc protector to the protected pipeline.
2. Electrical drainage protection is also a passive method, which is performed by connecting the pipeline to a ground loop, made in accordance with the PUE. This method helps to get rid of the occurrence of stray currents and is used if the pipeline is located near the contact electrical network of ground or rail transport.

Note! good example passive protective protection is the well-known zinc coating of iron products, or, more simply, galvanization.

Conclusion

Each of the above methods has its own advantages and disadvantages, so they should be used depending on the prevailing specific conditions. In conclusion, it should only be said that, regardless of the method chosen, the cost of repairing and replacing a pipeline will be much more expensive than the cost of the most complex and time-consuming protection.

For more information, you can watch the video in this article or read similar materials on our website.

Of the various types of pillars used to build a fence on summer cottages, in most cases pipes are used. Firstly, the material is from a moderate price category, durable, easy to use. Secondly, it goes well with other materials.
Depending on the type of barrier, they are selected different kinds pipes. Use round, rectangular and square. Round ones are slightly cheaper, but square or rectangular ones are stronger and easier to work with.
Painting fence posts will give not only an aesthetic appearance to the fence, but also protect pipes from corrosion. Whether the material has been used or new, the preparation requirements are the same.
For pre-treatment pipes will be needed:

• metal brush;
• brushes for power tools;
• grinding wheels;
• sandpaper;
• personal protective equipment.

The surface to be treated is thoroughly cleaned of rust and dirt. A tool suitable for this purpose is selected. For removing old paint flushing may be required. The stores offer a wide range of washes for old paint.

Bituminous mastic

Bituminous mastic is widely used in various construction works as protective and waterproofing material. In the case of supporting pillars, it is necessary to process with it that part of the pipes that will be buried or cemented. This will help protect the metal from water and salts dissolved in it.
Paint supporting pillars for the fence is possible before installation. At the same time, the drying time increases, since the lower plane is not painted, but to work with round material just difficult. In addition, it is quite easy to damage the finished surface. Therefore, it is better to apply paint after installation.

If welding is supposed to be carried out, then it is necessary to apply the coating after they are completed, carefully cleaning the welding seams!

bituminous varnish

Prepared pipes are degreased with an available solvent, and varnish is applied to the surface with a brush. The use of varnish does not require additional primer. If the varnish is too thick, it is diluted with white spirit. When buying bituminous varnish, you need to pay attention to the drying time. It can range from 1 to 48 hours.
Due to its high adhesive properties, it can be used as self coating and act as a primer.

Paint treatment

When choosing a paint, the main thing is to decide on the color scheme and buy material from one manufacturer. This will ensure that the color scheme does not change. In case of special wishes for the color scheme, you will have to use different types. When buying for mixing, consultation with a specialist is necessary, since not all paints can be mixed. They can curdle like milk, which can ruin the whole process. And since we are talking about a summer house, here we are talking about more economical options.
When painting, oil, acrylic, alkyd and other paints are used. It all depends on the wishes: matte or glossy finish will be at the exit.
Oil paints are considered the most economical, but have a number of disadvantages: they dry for a long time, do not withstand high temperatures poorly protected against corrosion.
Enamels harden faster, hold better and are more resistant to temperatures.

The ideal option would be acrylic paints. They are non-toxic, water-soluble, withstand high temperatures.

Before painting, the metal surface should be primed. For this, GF-021 or similar are most often used. It is gray and red-brown in color. To reduce the amount of paint used, a more suitable primer is selected. It is applied to a dry, clean surface with a brush, roller or using an airbrush in 1-2 layers.
After the primer dries, start painting. To prevent the primer from showing through, the paint will have to be applied in two layers.

Paint "Special Forces"

The obvious disadvantage of this product - high price. Otherwise perfect for working with metal surfaces. This is a three part paint. It contains a rust converter, primer and directly enamel.
When working with Spetsnaz, it is not required to apply soil and strongly clean the supports. Nevertheless, although it is written that it is applied to rust, it is better to remove it. Degreased with either white spirit or Thinner 647.
Paint is applied to the cleaned pipe with a brush. After the first layer, unpainted places are possible, but after the second layer is applied, there will be no such places. Three coats are required for outdoor applications. "Spetsnaz" dries quickly, therefore, being in an open jar for a long time, it begins to thicken. It is diluted to the desired consistency with the same white spirit.
The enamel is packaged in jars of 900 g and is available in ten colors. After drying, it becomes matte.
Now there are many names of three-in-one paints: Rust Stop, Stainless Steel, Hammerite and others. All of them are united by application to a rusty surface. Although it is better to clean up the conscience to clear one's conscience. And price category not cheap.
Although these types have their own advantages, many prefer a primer with or without subsequent painting.
Even for painting pipes, aluminum silver powder is used, which is dissolved in varnish for outdoor use.

General rules for painting work

In order to successfully complete the planned work, you should adhere to certain rules that can protect you from annoying mistakes.

1. Since most of the materials used are combustible, work should be carried out near open fire prohibited.
2. For painting, you should choose a dry warm day, as with strong sun the quality of the layer deteriorates.
3. If in doubt when buying, ask for a certificate for the product.
4. Use closed clothing and gloves to protect your body from paint.
5. Keep paints and varnishes and solvents away from direct sun rays and sources of fire.

Fulfilling these simple requirements, the fence will serve for a long time and will not require frequent repairs.

Metal pipes have many advantages, but during their operation, everyone can face one problem - corrosion. Corrosion of pipes leads to a reduction in their service life and the useless waste of a huge mass of metal, especially when it comes to steel pipes Oh. In connection with it, accidents and water leaks occur on water lines, because of it the roughness of the inner surface of the pipes increases, which is accompanied by the appearance of additional resistance, a drop in water pressure and, ultimately, an increase in the cost of its supply.
In other words, metal corrosion creates the need for additional construction and operating costs in water supply systems. That is why the fight against corrosion in plumbing practice is given special attention.

Causes of corrosion from outside and inside pipes

Both the inner and outer surface of the pipe walls suffer from metal corrosion. Corrosion from the outside of pipes occurs due to metal contact with the soil, so it is sometimes called soil corrosion. The salt solutions contained in the soil are liquid electrolytes, and therefore they destroy the structure of the metal during prolonged interaction with it. As a special characteristic of the soil, its corrosive activity is distinguished, which is inversely proportional to the electrical resistance of the soil, that is, the higher electrical resistance, the less corrosive activity of the soil, and vice versa - the lower the electrical resistance of the soil, the higher its corrosive activity. Due to the fact that this dependence is known, specialists can determine the corrosivity of soils by measuring only the level of their electrical resistance.
Corrosion inside pipes arises from the corrosive properties of the water itself. Low water pH indicator(pH) and high content oxygen, sulfates, chlorides and dissolved carbon dioxide quickly leads to corrosion of the inner surface of the walls of metal pipes.

Methods for protecting metal pipes from corrosion

External insulation

First and most important way there is external insulation. In addition to anti-corrosion functions, it reduces heat loss and provides mechanical protection. Can be used to create insulation different materials Let's take a quick look at the options.
1. Bituminous insulation. It consists of a layer of polyethylene, which is protected by a bituminous coating. Sometimes there may be fiberglass wrapped around the pipes. It can be used for pipelines that are placed in clay, sandy and rocky soils.
2. Polyethylene anti-corrosion insulation. It consists of a multi-layer coating, specially designed to protect pipelines from corrosion.
3. Polyurethane foam insulation. There are two kinds. The first is the use of polyurethane foam shells, used for ground and underground pipelines for channel and non-channel pipes. The second is the creation of a polyurethane foam shell by injecting liquid PU foam between the pipe and the previously created polyethylene insulation, after which the PU foam hardens and turns into a complete shell.

There is also glass wool insulation and mineral wool, however, these options were originally designed to reduce heat loss and prevent the creation of condensate, and not to protect against corrosion, which is why they are used primarily for insulating pipelines of heating networks.
It is possible to vary the thickness of the insulating layer. In each case, the thickness is calculated depending on the functional load on the pipeline, the importance of the water line and the corrosive activity of the soil in which it is placed - the higher this activity, the thicker the insulating layer should be.

Internal insulation

It is advisable to insulate pipes not only from the outside, but also inside. For example, in the USA for steel and cast iron pipes previously successfully used internal cement coating 3–6 millimeters thick, and this kept for a long time throughput pipelines on high level. May apply cement-sand mortars, varnishes. In addition, it is possible that the water itself through special treatment deprive it of its corrosive properties.

cathodic protection

Cathodic protection is another way to protect metal pipelines from corrosion, fundamentally different from those discussed above. It is based on electrochemical theory corrosion, according to which corrosion is associated with galvanic vapors that are formed in the area of ​​​​contact of metals with the soil environment, and the destruction of metals occurs in places where current flows out of it environment. Therefore, if you connect an external DC source and direct the current into the ground through the old iron pipes, rails and other metal objects, then the surface of the pipeline will turn into a cathode, which will protect it from the destructive influence of galvanic couples. And the current must be diverted from the pipeline through a special wire to the negative pole of an external source. The disadvantage of this method is energy consumption, so it is more often used as an additional, but not the main method.

Removal of water pipes from electric transport routes

Corrosion of metal pipes can be promoted by the effect of stray currents, which are especially exposed to pipes laid near the paths of intra-factory or urban electric transport. This is avoided in two ways - by removing water pipes from electric transport tracks and by adhering to the well-known rules for building railroads for electric transport.

Listed protection methods water pipes from corrosion are usually used in combination. These methods summarize the experience of many years of practice and various technical studies, so their effectiveness is not only proven, but also tested by life.

Corrosion is one of the main problems of all metal structures. Many experts believe that the appearance of rust is an inevitable process, and their only recommendation is to change metal pipes to plastic ones. However, given the fragility of plastic, such perturbations can not be carried out everywhere. In addition, the development of corrosion can be slowed down by significantly reducing its destructive effect.

There are several ways to combat corrosion of profile pipes in Moscow, and the easiest of them is to apply to metal special means forming a protective film on its surface. Such a tool can be paint, varnish or enamel. For coatings characterized by low gas permeability and gas permeability, as well as the ability to water repellency. Such coatings do not allow the metal to come into contact with moisture, oxygen and other aggressive substances that cause corrosion. Coatings are relatively inexpensive and very easy to apply. For this, an ordinary brush is used. A spray option is also available.

Protective qualities paintwork materials persist for several years, after which the layer must be updated. They have several disadvantages:

1. Do not withstand significant mechanical damage.
2. Not resistant to temperature changes.

As a result, over time, cracks form on the surface of painted pipes, so this type of protection should be carried out regularly.

How to properly prepare a pipe for painting

In order to reliably protect the pipe from corrosion, it is necessary not only to use high-quality protective substances, but also to take care of their correct application. First of all, it is necessary to achieve high adhesion, that is, the quality of adhesion of the applied composition to the metal. This method of combating corrosion on profile pipes in Moscow assumes a uniform layer of application, the absence of air bubbles and porosity. Therefore, the quality of the coating will directly depend on the preparation of the base.

Painting heating pipes is a typical task that occurs where the system has not been replaced with options made of plastic, stainless steel, copper. How to tidy up conventional system so that she has best view? The reliability of protection is also important, the paint must be resistant to temperatures and external influences, not to bring harmful substances inside the house. Therefore, its selection and application must be approached carefully ...

Pipes are serious...

Painting and protection of heating pipes is best done according to the rules, otherwise there will be increased costs.

If you do not make high-quality protection of steel pipes from the very beginning, then under a layer of paint the metal will rust. This will be manifested by swelling, peeling of the layer, rust in places. Then it will be necessary to mechanically peel off the rust and the old paint, after which ... do it according to the rules - there will be triple labor costs and financial frustration.

The intensity of corrosion will depend on the environment, on humidity. Outside, steel parts that are exposed to precipitation oxidize intensely. In contact with the ground, this process is even faster.

In a room, especially in a dry and heated one, this process is slow. But surely many have seen rust on radiators and pipes, even painted ones. How to process these parts reliably, especially when it comes to operation in adverse conditions?

Painting of steel parts

Steel and cast iron are painted according to the following scheme.

• 1. Mechanical removal rust, old paint, metal cleaning, solvent degreasing.
• 2. Treatment of the entire surface and internal cavities with a rust inhibitor. Orthophosphoric acid is more commonly used. This is an important point. When the acid reacts with iron oxides, stable substances are formed in the form of a film on the part.
• 3. Metal primer. Soil - a special composition that is firmly associated with the surface of the part, enters into the smallest irregularities. Forms a strong protective film. It is recommended to use only high-quality compositions.
• 4. Painting. The paint layer must be resistant to external influences. Preferably from the same manufacturer as the primer for the best combination.

Additional information - the sequence of work when painting and protecting elements of the heating system is shown in the figure.

What is the feature of heating protection

Heating pipes and radiators get hot. At the same time, they are located in residential premises. Therefore, the compositions that can be used for coloring heating system, must be:

• elastic, do not crack at constant temperature expansions. Do not lose adhesion to metal.
• do not emit any components, including when heated.

But not only that, for outdoor work, the compositions must also be resistant to freezing if the pipes hibernate without heating in open form. And also - to precipitation with aggressive acid-base water, and to ultraviolet radiation, if there is no external additional protection.

For outdoor use, the protection must be particularly resistant to electrochemical reactions, and for the ground - also to significant mechanical stress.

What is used for pipes

To the delight of the consumer, some modern paint products meet the above requirements. On sale you can find special formulations for hot heating systems.

As a rule, for pipes and radiators inside the house, surface paints are used on water based. They are considered the most harmless and do not smell. But fillers can be different.

For outdoor work, weatherproof compositions can be oil based. They dry longer, but the resistance of the film they created to exposure is more important there. aggressive waters. They can be applied to various pipes. True, the protection of heating mains outside buildings and in the ground is carried out in several other ways.

Heating main outside and underground

Heating pipes outside the building are usually thermally insulated. On them, in addition to the usual protection against corrosion, a sheath of insulation is installed. Thin pipes, which are used in private homes, are often put in a shell made of dense polyurethane foam or extruded polystyrene. These thermal insulation materials water-repellent, even if leakage occurs through outer coating, they will probably prevent the further spread of moisture.

The shell is put on the pipes in a checkerboard pattern, and the joints are glued with construction tape.

A roofing felt casing is glued over the thermal insulation using a composition that is not aggressive to polystyrenes, which acts as a long-term protection against moisture.

But large diameters are thermally insulated more often with rolled glass wool. This way is cheaper. A bituminous-roofing material cover is arranged on top.

The pipes themselves under thermal insulation are usually treated with a rust inhibitor and a high-quality primer.

New silver pipe

One of the reliable methods of protecting heating pipes that can be applied at home is coating with a zinc-polymer composition. The so-called "cold galvanizing". This is not at all what is called factory galvanization, but nevertheless, protection is advertised as something else. Zinc dust is added to the polymer-epoxy composition, with a chip size of less than 10 microns. Suitable as a replacement for the usual "silver", as an option, although not cheap, but as an interesting experiment ....

What compositions are used - how to paint?

Currently widely used for painting pipes next series colors

These and other coatings for heating pipes and radiators can be found on store shelves. Indeed, they are only part of necessary protection metal from corrosion. Full painting includes the processes that were listed above.