How to protect the pipe from corrosion. How to paint and protect heating pipes

Do you want to know what is the most effective corrosion protection for steel pipes? Metal pipes during operation are constantly exposed to various adverse factors. To solve this problem, a comprehensive protection of pipelines against corrosion according to SNiP 2.03.11-85 "Protection of building structures against corrosion" has been specially developed.

External polymer coating - reliable protection against corrosion of steel pipes

Corrosion Control Methods

In this article, the reader is offered a detailed instruction, which describes in detail the basic principles for the implementation of anti-corrosion protection for metal products. I will tell you how to protect any metal surface from corrosion.

Classification of harmful factors

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. 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 arises as a result of the interaction of iron with various active chemical compounds (acids, alkalis, etc.). In this case, the ongoing chemical reactions lead to the formation of other compounds (salts, oxides, etc.), which, like rust, gradually destroy the metal.
2. Electrochemical corrosion occurs when the iron product is in the electrolyte environment for a long time (an aqueous solution of 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 causes it to freeze. Upon transition to a solid state of aggregation, a crystal lattice is formed in water, as a result of which its volume increases by 9%. Being in a confined 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. In order to prevent rupture of pipes and damage to supporting 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 an 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 of the 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. Chemical composition and the 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. Quality indicator of acidity soil, which can cause both chemical oxidation and electrochemical corrosion of the metal.
3. Earth electrical resistance. The lower the electrical resistance value, the more susceptible the metal is to damage caused by electrochemical emission.

Note!

To obtain objective analysis results, 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 laying of water and sewer networks, 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. Underground pipeline laying at depth exceeding the maximum depth of soil freezing for a given region.
2. thermal insulation air and underground lines using various materials with low thermal conductivity (mineral wool, foam plastic segments, foam sleeves).

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

The most advanced method of 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 by the 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.

I will give simple examples:

1. The most common protective coating option is ordinary waterproof paint or enamel. For example, the protection of a gas pipe passing through the air is always done with yellow weather-resistant enamel;
2. Underground water and gas pipelines are assembled from steel pipes, which are pre-coated on the outside with a thick layer of bituminous mastic, and then wrapped with thick technical paper:
3. Coatings made of composite or polymeric materials also have high efficiency;
4. Cast iron elements of sewer communications are covered from the inside and outside with a thick layer of cement-sand mortar, which, after solidification, forms a uniform monolithic surface. Thus, you can protect the support.

In order to choose the right material for the outer coating, you need to know that the anti-corrosion protection of the metal must simultaneously have several qualities.

1. Paintwork after drying, it should have a continuous, uniform surface with high mechanical strength and absolute resistance to water;
2. Protective film waterproofing material, with the specified properties, must be elastic and not collapse under the influence of high or low temperatures;
3. Raw material for coating, it must have good fluidity, high covering power, as well as good adhesion to the metal surface;
4. Anti-corrosion treatment applied to a dry, cleaned metal surface;
5. Electrical conductivity. Another indicator of a quality insulating material is that it must be an absolute dielectric. This property provides reliable protection of pipelines from stray currents, which increase the adverse effects of electrochemical corrosion.

Note!

The most effective solutions for waterproofing metal are considered to be compositions based on bituminous resins, two-component polymer compositions, as well as self-adhesive polymer roll materials.

Active and passive electrochemical protection

Underground engineering communications are 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 direct current circuit:

• To do this, 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 the voltage is applied, the electrical circuit is completed 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 tread protection piping is as follows:

• An electrode made of a more electronegative metal, such as zinc or magnesium, is placed next to iron in the ground;
• The steel pipe and the electrode are connected electrically through a controlled load;
• In the electrolyte environment, they form a galvanic couple, which during the reaction causes the movement of electrons from the zinc protector to the protected pipeline.

3.Electrical drainage protection is also a passive method, which is performed by connecting the pipeline to the ground loop:

• Connection is made in accordance with the requirements of 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!

A good example of passive tread 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 specific conditions. In conclusion, I can only say 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.

Without reliable anti-corrosion protection, not a single metal structure will last for a long time. Rust protection is important unless you plan on replacing your fence every few years.

Metal fences are no exception. You can extend the life of products by properly processing them. Below we will talk about the technology for painting structures made of metal picket fence, profiled sheet and mesh, as well as analyze the coloring compositions that are best suited for metal surfaces.

Rust protection for the fence in stages

We start by preparing the metal for painting

This moment is fundamental, since it determines how well the finishing layer will lie on the fences from the eurostudent or profiled sheet. First you need to clean the fence from traces of paint, rust, oil, grease, dirt. Conservative and radical methods are appropriate here.

• Conservative ones include cleaning rust with a scraper, a metal brush, a special knife. The best result will give an acetylene torch or a blowtorch.
• When exposed to metal, the outer layer of paint burns out, and rust and scale move away due to temperature differences. If it is not possible to remove traces of corrosion, choose a coloring composition that is suitable for application to an unprepared surface.

Padding

The next stage is the application of a primer, which simultaneously protects the metal from corrosion and ensures that the paint adheres to the surface. For ferrous metals, experts recommend choosing anti-corrosion primers.

For non-ferrous, on the contrary, the property of adhesion is more important (aluminum and copper are not subject to corrosion). The primer coat can be applied with a roller, brush or sprayer.

Applying the finish coat

After the primer layer is applied, you can start painting. It can be applied with a sprayer, brush or roller.

It is better to paint in 2-3 layers with drying intervals. This will give a more uniform surface without flaws. The sprayer is the easiest to use. To do this, you need to process the surface from a distance of 15-20 cm.

The exposure time between layers is reduced to 20 minutes. Rollers are used for flat surfaces. Before painting, it is recommended to dilute the mixture with a solvent in a ratio of 9 to 1. Hard-to-reach places and corners are treated with a brush. Then all the fences are rolled in 2-3 layers.

The choice of paint for metal

On the website masterovit.ru (the largest manufacturer of metal fences in the Russian Federation in 2015) there was a recent discussion on how to properly paint an inexpensive corrugated fence and what paintwork materials are best to choose.

The company's specialists recommend water-dispersion and special acrylic paints for metal. The latter option is preferable, since it allows you to reliably protect the surface from corrosion and negative external factors (precipitation, UV radiation).

A good solution is the choice of anti-corrosion compounds that are allowed to be applied to traces of rust and paint residue. The compositions contain a solvent, so they remove the old layer and protect structures from destruction. There are also enamels with additives on the market: rust converters, anti-corrosion primers. They are applied to clean surfaces.

Pre-treatment of the base with a primer is not required, which reduces the process of painting the fence. For ferrous metals, water-based anti-corrosion compounds are optimal. The topcoat is highly resistant to ultraviolet radiation, rainfall, sudden changes in temperature.

Under its influence, the metal of the pipes is destroyed, which leads to the formation of corrosive fistulas, cracks in the places of bends, and divergence of the seams. Cold water pipes are especially affected. If your immediate plans do not include replacing the pipes of intra-apartment pipelines with stainless ones (galvanized, plastic, metal-plastic), then measures must be taken to protect the pipes from corrosion.

The most common (and also the easiest) way to protect metal surfaces from rust is to coat them with anti-corrosion compounds. Cold water pipes can be primed with ready-made compounds GF-021, GF-032, KF-OZO, PF-046, FL-053, EP-076 and XC-068. An excellent protective agent can be prepared at home. Mix 150 g of red lead, 150 g of iron red lead and 100 g of drying oil and cover the steel pipes with the resulting composition.

Painting pipes is a good protection against rust, the main thing is that paints and varnishes are moisture resistant, and paints intended for painting hot water pipes are also heat resistant. Before painting the surface, it is recommended to prime with a lead-red lead or similar primer.

If individual sections of pipelines are laid hidden, then it makes sense for them to select means of more reliable protection.

An effective, but rather time-consuming way to protect pipelines from corrosion is the following (it is applicable only if the pipes were not previously coated with any compounds; it is rational to carry out such protection even at the stage of laying the pipeline). If there is rust on the pipes, clean it off and cover the pipes with a mixture of casein glue and cement. When the casein solution is dry, oil the pipes and coat them with oil paint.

Coating pipes with carbolate not only prevents the formation of condensate, but also protects them from corrosion.

Steel outlets and cast iron siphons can be treated against corrosion with one of the following compounds:

• bakelite-aluminum - combine 1 weight part of aluminum powder and 9 weight parts of bakelite varnish and mix well;
• ethinol-aluminum - combine 0.7 parts by weight of aluminum powder and 9.3 parts by weight of ethinol varnish and mix well;
• ethinol-glue - combine 1 weight part of BF-2 glue and 7 weight parts of ethinol varnish and mix well.

Not only steel pipes are susceptible to corrosion, but also parts made of other metals, therefore it is recommended to protect all corrosive elements of pipelines from rust. So, on chrome-plated surfaces in conditions of high humidity, a rusty rash may appear. Its formation helps prevent unvitaminated and unsalted fish oils. If the weather is hot in summer, and the room is well heated in winter, then the treatment of chrome surfaces is carried out every 10-15 days. Wipe the chrome parts with a swab dipped in fish oil, and after a while wipe them with a dry soft cloth. Before the next treatment, remove the remnants of grease from the previous treatment with a soft cloth moistened with gasoline. This simple measure allows you to protect chrome surfaces from a rusty rash for several years.

If rust has already formed on nickel or chrome surfaces (such as faucets), rub the rusted areas with a rag soaked in warm vinegar to remove it. You can also remove rust from nickel-plated parts with fat (animal or fish). Apply a layer of grease to the rusty stain and leave it for a few days, after which remove the remaining grease with a soft cloth moistened with ammonia.

The following composition will help to free chrome coatings from rust: 200 g of copper sulfate and 50 g of concentrated hydrochloric acid should be dissolved in 1 liter of water. In the resulting composition, moisten a cloth swab and rub it with rusty spots until completely removed. To neutralize the acid, rinse surfaces, then rinse with clean water and dry with a soft cloth.

Yellow "rusty" stains on the surfaces of bathtubs, sinks, sinks and shower trays can be removed with slightly salted heated vinegar.

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 a conventional system so that it looks its best? 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 of rust, old paint, cleaning of dirt to metal, 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 to paint the heating system should 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 the open. 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 compositions for heating heating systems.

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

For outdoor use, oil-based formulations can be weatherproof. They dry longer, but the resistance of the film they created to the effects of aggressive waters is more important there. 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 that are used in private homes are often wrapped in a shell made of dense polyurethane foam or extruded polystyrene. These thermal insulation materials are water-repellent, even if leakage occurs through the outer coating, they are likely to prevent further moisture from spreading.

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 larger 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?

At present, the following series of paints are widely used for painting pipes

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

Corrosion is the scourge of all metal structures, and leaking pipes are a nightmare for any homeowner. The appearance of rust is inevitable, like the change of seasons, it is caused by physical and chemical environmental factors. But it is possible to slow down the development of corrosion and reduce its destructive effect.

Metal and plastic: pros and cons

The common opinion of experts in the field of repair says that there is only one radical way to combat corrosion - replacing all pipes with plastic ones. But metal pipes do not give up so easily, because it is not always possible to make major repairs in the entire apartment. In addition, steel and cast iron pipes are much stronger and more reliable than plastic and metal-plastic ones. They are more resistant to high pressure and temperature (especially to their differences), have a low coefficient of thermal expansion (do not deform) and high thermal conductivity.

Plastic is theoretically very durable, but this has not yet been tested by time. The safety of this material in its long-term use has not been sufficiently studied, but it is already known that it is afraid of chlorinated water. So metal pipes still have a place in our homes, which means that the problem of their protection against corrosion is still relevant.

Around the aggression!

How to deal with rust at home? The most affordable way is to apply a product to the metal that forms a protective film on its surface: paint, varnish, enamel. Paint coatings have low vapor and gas permeability and high water-repellent properties. Thus, they do not allow moisture, oxygen and other aggressive substances to the metal surface, which cause corrosion. Paints are relatively inexpensive, easy to apply with a regular brush or spray. They retain their protective properties for several years. Their important quality is resistance to high temperatures, the main drawback is sensitivity to mechanical damage and temperature changes, due to which small cracks form on the surface, opening access to moisture and air to the metal. Therefore, staining should be carried out regularly.

Main quality!

The barrier in the form of paintwork materials does not stop corrosion completely, but only slows it down. Therefore, the quality of the coating comes to the fore - high strength of adhesion of the composition to the base (adhesion), uniformity of application, absence of porosity and air bubbles. And the quality of the coating is directly related to how the base is prepared. Old, peeling paint must be carefully removed. If the pipe is rusty, then you need to clean off the loose layers, and then use a special rust converter (150-200 rubles / kg). The basis of such funds is acid (usually orthophosphoric). It chemically interacts with rust and turns it into iron salts - a neutral substance that forms a uniform and durable additional protective film.

Next, an anti-corrosion primer should be applied, and only then - a paint compatible with the primer. The thicker the layer of the latter, the worse the adhesion to the base. Therefore, the main rule is that several thin layers of coating are better than one thick one.

The range of anti-corrosion coatings is quite extensive. The simplest ones are GF-021 primer (the cost of this product from Khimservice is 50 rubles / kg) and PF-115 enamel (for example, the price for this material from RegionSnab is 48 rubles / kg). More expensive, but also effective - polyurethane, alkyd, epoxy coatings, which not only protect the metal well, but also have excellent decorative properties (in particular, "liquid plastic" enamel). It is good if the paint contains corrosion inhibitors - substances that slow down oxidation. The most convenient to use products that are united by the name "3 in 1 rust paint" (about 200 rubles / kg) - they simultaneously contain a rust converter, anti-corrosion primer and wear-resistant enamel.

What's underground?

Pipes passing underground are especially susceptible to corrosion - in a suburban area you can’t do without them. A different corrosion mechanism occurs in soil than in the atmosphere. The main cause of soil corrosion is electrochemical factors: a metal pipe in the soil becomes an electrode, and wet earth becomes an electrolyte.

To isolate the pipeline from this aggressive environment, paintwork materials are unsuitable, since the protective layer is mechanically damaged when it comes into contact with the ground. Much more practical are elastic coatings based on coal tar (bitumen) with various additives, mineral or polymer, that increase its strength. Such a mixture is called bituminous mastic (from 25 rubles / kg). Another option is to wrap the pipes with any insulating material, for example, waterproofing (from 40 rubles / sq. M), which is asbestos paper coated with bitumen with the addition of cellulose.

What's new?

A relatively new effective and inexpensive method of protection against soil corrosion is the use of geotextiles (from 20 rubles/sq. m.). This non-woven polymer fabric has excellent water and air permeability, is durable, wear-resistant and withstands high mechanical loads and aggressive environments. Geotextile creates a reliable separating layer between the pipe and the soil. The best effect will give the simultaneous wrapping of the pipe, lining the trench and good drainage. At the same time, water entering the soil does not linger, which means that it does not have time to act on the protective coating of the pipe. Synthetics practically do not decompose in the soil, which allows drainage based on it to function for a long time. Working with geotextiles is simple and does not require special skills.

A truly unique method of protection is cold galvanizing. Metal-polymer compositions (200-350 rubles / kg) have a protective effect, which is comparable to galvanizing performed in the traditional way - hot or galvanic. Such compositions provide protection in water, soil, atmosphere for many years, they are used both for obtaining independent protective coatings and as primers before applying coatings. The cold galvanizing system contains a binder - polystyrene, epoxy, alkyd and other bases and zinc powder ("zinc dust"), in which about 95% of metallic zinc with a particle size of less than 10 microns. The composition is applied like ordinary paint - with a brush or roller. After drying, a polymer-zinc film is formed on the surface, which combines all the advantages of polymer and zinc coatings: the first forms a mechanical barrier protection, and the second - an electrochemical one. In addition, such a coating is sufficiently elastic and does not give microcracks, and it is also easy to repair.

Proper anti-corrosion protection will help preserve the original appearance of various metal structures and pipes. Subject to the choice of quality materials, proper application, careful preparation of the surface, it will save you unnecessary costs, save time and effort.