Corrosion is the scourge of all metal structures, and leaking pipes are every homeowner’s nightmare. 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 effects.
Metal and plastic: pros and cons
The common opinion of experts in the field of repair is that there is only one radical way to combat corrosion - replacing all pipes with plastic ones. But metal pipes don’t give up so easily, because it’s not always possible to make major renovation throughout the 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 blood 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 during 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 protecting them from corrosion is still relevant.
There is aggression all around!
How to deal with rust in living conditions? Most affordable way- applying a product to the metal that forms protective film on its surface: paint, varnish, enamel. Paint and varnish coatings have low vapor and gas permeability and high water repellent properties. Thus, they do not allow moisture, oxygen and other aggressive substances, which cause corrosion, to reach the metal surface. Paintwork materials are relatively inexpensive and can be easily applied with a regular brush or spray. They retain their protective properties for several years. Their important quality- resistance to high temperatures, the main disadvantage is sensitivity to mechanical damage and temperature changes, due to which small cracks form on the surface, allowing moisture and air access to the metal. Therefore, staining should be done regularly.
Main quality!
A 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), uniform application, absence of porosity and air bubbles. And the quality of the coating is directly related to how the base is prepared. Old, flaking 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). These products are based on acid (usually phosphoric acid). It chemically interacts with rust and turns it into iron salts - a neutral substance that forms a uniform and durable additional protective film.
Next, apply an anti-corrosion primer and only then apply 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 primer GF-021 (cost of this product from the Khimservis company is 50 rubles/kg) and PF-115 enamel (for example, the price for this material from the RegionSnab company 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, enamel " liquid plastic"). It’s good if the paint contains corrosion inhibitors - substances that slow down oxidation. The most convenient to use products are those that are combined under the name “rust paint 3 in 1” (about 200 rubles/kg) - they simultaneously contain a rust converter, an anti-corrosion primer and wear-resistant enamel.
What's underground?
Pipes running underground are especially susceptible to corrosion. suburban area There is no way to do without them. A different corrosion mechanism occurs in the soil than in the atmosphere. The main cause of soil corrosion is electrochemical factors: a metal pipe in the ground becomes an electrode, and wet soil becomes an electrolyte.
Paintwork materials are not suitable for isolating a pipeline from this aggressive environment, since the protective layer is mechanically damaged upon 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. This mixture is called bitumen mastic(from 25 rub./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 breathability, is durable, wear-resistant and can withstand high mechanical loads and exposure to aggressive environments. Geotextiles create a reliable separation layer between the pipe and the soil. The best effect will be achieved by simultaneously wrapping the pipe, lining the trench and good drainage. In this case, the water entering the ground is not retained, which means it does not have time to affect the protective coating of the pipe. Synthetics practically do not decompose in the soil, which allows drainage based on them to function for a long time. Working with geotextiles is simple and does not require special qualifications.
A truly unique method of protection is cold galvanizing. Metal-polymer compositions (200-350 rubles/kg) have a protective effect that is comparable to galvanizing performed traditional way- hot or galvanic. Such compositions provide protection in water, soil, and atmosphere for many years; they are used both to obtain independent protective coatings, and as primers before applying paint and varnish. The cold galvanizing system contains a binder - polystyrene, epoxy, alkyd and other bases and zinc powder (“zinc dust”), in which approximately 95% of metallic zinc is present with a particle size of less than 10 microns. Apply the composition as regular paint- with a brush or roller. After drying, a polymer-zinc film is formed on the surface, combining all the advantages of polymer and zinc coatings: the first forms a mechanical barrier protection, and the second - electrochemical. In addition, this coating is quite elastic and does not give microcracks, and it is also easy to repair.
Proper anti-corrosion protection will help maintain its original appearance. various designs and metal pipes. Subject to choice quality materials, correct application, thorough surface preparation will save you from extra costs, will save time and effort.
Weakness metal pipes- susceptibility to corrosion. Over time, cast iron and steel pipes inevitably rust, and this affects performance characteristics pipeline is not in the best way. To ensure that the pipeline lasts longer and its condition does not negatively affect the quality of water, rust should be removed in a timely manner.
Rust affects not only the fact that in places where plaque has formed, the pipe can simply leak, but also the quality of the transported liquid. Water in rusty pipes has bad smell and becomes suitable only for technical use.
Corrosion in heating pipes reduces heating efficiency, which inevitably increases operating costs.
Methods for cleaning rusty pipes
Corrosion can occur both externally and internally. inside pipes. Cleaning methods depend on the location of the plaque and the degree of damage.
You should not remove rust from heavily rusted pipes - this can lead to damage, and as a result, the pipe will become unusable. Therefore, in case of severe corrosion, it is much more expedient to simply replace the damaged section of the pipeline or the entire line.
Only if the pipe is slightly damaged by rust, cleaning will be effective and will increase the life of the pipe for some time.
Cleaning the pipe outside
If the pipe is rusty on the outside, you can use the following to clean it:
Note! Special means To remove rust, it should be used strictly following the instructions and dosage. They contain strong alkalis, which, if the instructions are not followed, can damage the pipes.
Cleaning the pipe from the inside
In addition to corrosion, scale and various deposits accumulate on the inner walls of pipes. To save throughput pipes, it is necessary to regularly clean and rinse it from the inside for preventive purposes.
Without reliable anti-corrosion protection it will not last for a long time none metal structure. Rust protection is important unless you plan to replace the fence every few years.
Metal fencing is no exception. The service life of products can be extended by proper processing. Below we will talk about the technology of painting structures made of metal picket fences, profiled sheets and mesh, and also analyze the painting compositions that are optimally suited for metal surfaces.
Rust protection for fences step by step
We start by preparing the metal for painting.
This point is fundamental, as it determines how well it will fit on fences made of Euro picket fences or corrugated sheets. finishing layer. First you need to clean the fence from traces of paint, rust, oil, grease, and dirt. Conservative and radical methods are appropriate here.
- Conservative methods include removing rust using a scraper, a metal brush, special knife. Best result An acetylene torch or blowtorch will do.
- When exposed to metal, the outer layer of paint fades, and rust and scale come off due to temperature differences. If it is not possible to remove traces of corrosion, choose a paint composition that is suitable for application to an unprepared surface.
Padding
The next step is applying a primer, which simultaneously protects the metal from corrosion and ensures the paint adheres to the surface. For ferrous metals, experts recommend choosing anti-corrosion primers.
For people of color, on the contrary, property is more important adhesion (aluminum and copper are not subject to corrosion). The primer coat can be applied using a roller, brush or sprayer.
Applying the finishing coat
Once the primer coat has been applied, you can begin painting. You can apply paintwork using 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 blemishes. It is most convenient to use a spray bottle. To do this, you need to treat the surface from a distance of 15-20 cm.
The dwell time between coats is reduced to 20 minutes. Rollers are used for smooth 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 the corners are treated with a brush. Then the entire fence is rolled with a roller in 2-3 layers.
Choosing paint for metal
On the website masterovit.ru (the largest manufacturer metal fencing in the Russian Federation based on the results of 2015) there was recently a discussion on how to properly paint inexpensive fence from corrugated sheets and which paint and varnish materials are better to choose.
The company’s specialists recommend water-dispersed and special acrylic paints on metal. Last option preferable, since it allows you to reliably protect the surface from corrosion and negative external factors(precipitation, UV radiation).
A good solution is to choose anti-corrosion compounds that can be applied to traces of rust and paint residues. The formulations contain a solvent, so they eliminate old layer and protect structures from destruction. There are also enamels on the market with additives: rust converters, anti-corrosion primer. They are applied to cleaned surfaces.
Pre-treatment of the base with a primer is not required, which shortens the process of painting the fence. For ferrous metals, anti-corrosion compounds based on water based. The finish is different high degree resistance to ultraviolet radiation, rainfall, sudden temperature changes.
There are many options for building fences, and their differences depend on the functions for which they are intended. The material of the future fencing is selected in accordance with the functions.
Functions and material of the fence
The fence is intended for simple and specialized fencing of the territory: land privately owned, parking areas, recreation areas, construction and specially protected sites, animal shelters. Fences are also often a decorative element in landscape design or form a single composition with architectural solutions.
This variety of functionality makes it possible to use different materials for their construction: ordinary wooden or metal picket fence, decorative picket fence in the “Ranch” style, multi-colored profiled sheets, chain-link mesh, welded, sectional, forged, asbestos-cement and concrete spans. Like any structure, a fence requires the creation of some kind of base on which the material is attached. For a fence, the pillars are such a basis.
Pole material
Regardless of the choice of material for the fence itself, the posts can be made from:
- wood;
- metal;
- concrete;
- bricks;
- asbestos cement pipes.
Metal advantage
Universal materials for making fence posts are hardware, because in the vast majority of fence installation cases welding is used.
A special quality of metal poles is their durability. No matter how you process it wooden beam, it will rot much faster than the metal will collapse.
The process of metal corrosion occurs on average at 0.15 – 0.2 mm per year. This depends on external weather and climatic conditions, the composition of the metal and the quality of its processing. A positive advantage of metal poles is reliability and strength. Asbestos concrete pipes are not subject to corrosion and do not require additional maintenance, but they are fragile and cannot withstand rough mechanical loads.
Pillars made of metal, compared to reinforced concrete ones, are easy to repair and install, dismantle and can be reused.
Corrosion
Metal corrosion is a natural phenomenon, which cannot be completely prevented, but this destructive process can be significantly slowed down. The oxidation process occurs with the participation of oxygen and aqueous solutions containing acid, alkali or salt.
In nature, iron is in pure form not found, but found in iron ore. Humanity invented the production of steel and came up with ways to preserve it. Factories use methods of phosphating steel by immersing it in various solutions, as well as electrochemical treatment. This coating is in the nature of a primer and requires subsequent painting. Steel is coated with other metals. Cheaper ones are aluminum and zinc.
There are silicate coatings - these are various types enamels. Enamel is fragile and not entirely suitable for a fence. Cement has approximately the same expansion temperature as steel and serves as an insulator against aggressive environments. Good insulation is a polymer film applied in several layers in the factory.
Treatment
The durability of the metal depends on the grade of steel. More precisely, there is alloy steel with different additives. But for simple fence- this is an expensive pleasure. Usually they use factory rolled metal, or make poles with their own hands from what they can get. For temporary fences, poles welded from pieces of iron or previously used but still strong water supply pipes are suitable.
It is difficult to clean the internal cavity of the pipe, but the rust is removed from the outside using an iron brush and treated with a grinder or grinder. If necessary, degrease and apply a primer for metal, for example, GF-021. After the primer has dried, the pipe is painted in two layers.
To paint metal, the most common oil paint PF-115 is suitable. For the lazy, there is three-in-one paint. It neutralizes rust, primes and creates a protective surface.
But in practice, without prior machining It’s better not to do without, you need to at least clean the metal with sandpaper.
The most the best solution to select new fence posts there will be a combined version of metal coated with zinc and polymer film. Factory metal rolling produces painting, observing all technologies. It is best to purchase poles that are ready for installation, as this will significantly save time and labor costs. However, this option cannot be called financially economical.
In practice, most often iron poles are primed and painted themselves oil paint or bitumen varnish
There are special cans of spray paint that are convenient to use when welding work. Coating powder paint will be more expensive and technically more difficult. The thinner the coating layer, the more durable the protection. Therefore, apply several layers with a spray or thoroughly rub in with a brush, avoiding air bubbles that provoke an oxide reaction.
The soil is more aggressive environment than air. Therefore, the part of the metal located in the ground is insulated with concrete or bitumen mastic. Rolled insulators are not suitable for these purposes. Scale generated during welding stimulates metal corrosion. It must be removed with a grinder.
Shapes of metal pillars
Fence posts can have a wide variety of configurations, from simple to designer:
- round;
- square;
- rectangular;
- screw;
- homemade.
Round pipes Easiest and cheapest to purchase. The choice of their diameter depends on the design of the fence, and most often they use a size from 57 mm to 108 mm, in exclusive options the diameter is increased to 159 mm. The thickness is selected taking into account the characteristics of the material filling the spans: from 1.5 mm to 4 mm. The thicker the longer term operation.
A good option with drill pipes with a wall thickness of 5 mm.
Transverse logs are attached directly to the pipes by welding, or guides for fastening are welded onto the pipes. The guides can be made in advance by welding them to a clamp, which is put on the pipe and tightened with a bolt. With this installation option, an insulating pad made of cotton material or a special plastic lining suitable for the diameter of the pipe is placed under the clamp.
Profiled posts have the shape of a square or rectangle. This form makes it possible to fasten the logs not only by welding, but also by using bolts or rivets. It is more convenient to work with them if the guide logs are made of wood or the fence is built in the “Ranch” style.
Screw posts are a pipe with a drill welded at its end. This option is used for quick installation fence, because there is no need to dig a hole for the post first.
Homemade pillars made from used material that is available (orphan), or from that which can be obtained. For example, iron corners are suitable.
Ground influence and installation
The choice of metal poles also depends on the installation method, and this, in turn, depends on the condition of the soil. For a light fence, you just need to drive a post into the ground if it is dense (gray soil, clay, sand). Two people are involved in the work - one drives it in, and the other holds the post, checking it for level in two vertical planes.
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 waste of a huge mass of metal, especially if we're talking about O steel pipes Oh. In connection with it, accidents and water leaks occur on water supply 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 special attention is paid to the fight against corrosion in plumbing practice.
Causes of corrosion from outside and inside pipes
Both the internal and external surfaces of pipe walls suffer from metal corrosion. Corrosion from outside pipes occurs due to metal contact with soil, which is why it is sometimes called soil corrosion. Solutions of salts 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 soil, its corrosive activity is distinguished, which is in reverse proportional connection with 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. Thanks to the fact that this dependence is known, specialists can determine the corrosive activity of soils by measuring only the level of their electrical resistance.
Corrosion inside pipes occurs from the corrosive properties of the water itself. Water with a low pH value and a high content of 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
The first and most important way is external insulation. In addition to anti-corrosion functions, it reduces heat loss and provides mechanical protection. Different materials can be used to create insulation; we will briefly consider the possible options.
1. Bitumen insulation. Consists of a layer of polyethylene that is protected bitumen coating. Sometimes there may be fiberglass wrapped around the pipes. Can be used for pipelines located 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 types. The first is the use of polyurethane foam shells, used for above-ground and underground pipelines for channel and non-channel pipe installation. The second is the creation of a polyurethane foam shell by injecting liquid polyurethane foam between the pipe and pre-created polyethylene insulation, after which the polyurethane foam hardens and turns into a complete shell.
There is also glass wool insulation and mineral wool, however, these options are initially intended to reduce heat loss and prevent the creation of condensation, and not to protect against corrosion, which is why they are used primarily for insulating pipelines of heating networks.
The thickness of the insulating layer can vary. In each specific 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 located - 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 from the inside. For example, in the USA for steel and cast iron pipes Previously, an internal cement coating with a thickness of 3–6 millimeters was successfully used, and this maintained the pipeline capacity for a long time at high level. Can be applied cement-sand mortars, varnishes. In addition, it is possible to deprive the water itself of its corrosive properties through special treatment.
Cathodic protection
Cathodic protection is another method of protecting metal pipelines from corrosion, fundamentally different from those discussed above. It is based on the electrochemical theory of 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 leaves it. environment. Therefore, if you connect an external source direct current and direct the current into the ground through old iron pipes, rails and others previously buried near the pipeline 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 external source. The disadvantage of this method is that it requires energy, so it is often used as an additional, but not the main method.
Removing water pipes from electric transport routes
Corrosion of metal pipes can be facilitated by the influence of stray currents, which are especially exposed to pipes laid near the tracks of intra-factory or urban electric transport. This can be avoided in two ways - by removing water pipes from electric transport tracks and adhering to the well-known rules for constructing rail roads for electric transport.
Listed protection methods water pipes against 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.