To ensure the durability of metal products, anti-corrosion treatment of metal structures is used. This procedure is designed to protect structures from exposure to aggressive environments and atmospheric precipitation. Thanks to the coating, the metal surface retains its original properties, including aesthetic ones.
The essence of the process
Corrosion is the process of electrochemical or chemical interaction of a metal with its environment, due to which the metal is oxidized and destroyed. Experts say that the damage from corrosion in the industrial sector reaches 4% of the gross national product of any country. Corrosion occurs due to exposure to metal oxygen, water, therefore, timely anticorrosion treatment of metal structures is required. The technology involves surface treatment with a thin layer of metal, metal alloys or non-metallic compositions.
Processing Features
Due to the fact that the metal begins to collapse under the influence of an aggressive environment, the strength and physicochemical properties of metal products change. And this affects the decrease in their functionality and durability. Corrosion contributes to the failure of equipment, vehicles. That is why the anti-corrosion treatment of metal structures plays an important role, the technology of which is constantly being modernized and improved.
Outside processing
External surfaces of metal products are most susceptible to aggressive factors. To protect them, constructive protection methods are used. They are used in the design and manufacture of products even before the active exploitation of metal elements begins. Constructive methods involve the selection of a material that can withstand the effects of the environment. For these purposes, steel with a durable film, high polymer materials, ceramics, and glass are well suited. In addition, anti-corrosion treatment of metal structures is accompanied by methods of rational use of products:
- elimination of cracks, cracks, gaps that may remain in the product and through which moisture may enter;
- the elimination of areas in which moisture may stagnate;
- surface protection from water;
- the introduction of inhibitors in an aggressive environment.
Passive protection
When using passive methods of protection, the metal surface is treated with some kind of coating, the task of which is to prevent the contact of metal and oxygen or metal and moisture. To this end, anti-corrosion treatment of metal structures is carried out. Materials for this are used modern, with improved performance properties. Such coatings perform several functions:
- barrier;
- tread;
- transformative;
- passive.
Barrier protection involves mechanical isolation of the metal surface. Most often, such tools are used for processing ferrous metals. But if the integrity of the protective film is compromised, under-film corrosion may occur under it.
What materials?
When anti-corrosion treatment of metal structures is carried out, the means are selected very carefully. To passivate surfaces, paints and varnishes containing phosphate acid or chromate pigments that slow down corrosion processes are used. When applying passivating primers, a spray gun is used. Depending on how many components are in these compositions, they can be used for processing both ferrous and non-ferrous metals.
Passive processing can also act as a protector, but in this case, paints are used in which more than 86% of the metal dust from an element of high reduction ability compared to the surface being treated. In most cases, when anti-corrosion treatment of metal structures is used, paints are selected with the filling of highly dispersed zinc powder. This technology is called cold galvanizing, which increases the service life of the metal surface and its resistance to abrasion.
Paints and enamels
Protection of metal structures is based on three types of products:
- Paintwork, which is easy and simple to apply and presented in a variety of colors. Using paints, you can process metal structures of large sizes and any configurations.
- Plastic anti-corrosion coatings, which are based on fluoroplastic, nylon, PVC. These compositions are characterized by high water, acid and alkali resistance.
- Rubber based coatings are used when anticorrosion treatment of tanks and metal structures is carried out from the inside.
Active protection methods
Metal requires special protection, for which active methods are used. Resistance of metal products to external factors is achieved:
- Hot-dip galvanizing of parts: according to this technology, the part is first degreased, then sandblasted or etched with acid, as a result of which it is coated with a thin zinc layer. A chemical reaction causes a protective film to form on the metal surface. It shields the metal and protects it from moisture. Most often, hot dip galvanizing is used to process large objects - tanks, tanks.
- Electrochemical galvanizing: this method involves the diffusion extraction of zinc ions from a slightly acidic solution during electrolysis. The galvanic processing of metal structures is used for the processing of metal products, parts of medium size.
- Thermal diffusion zinc coating: with this technology, zinc atoms penetrate the surface of iron under the influence of high temperature. The coating is strong and wear-resistant, and the original part is repeated completely, even if the surface is with recesses or relief.
Corrosion treatment of metal structures can be carried out in addition to electrochemical protection.
Modern methods
Most often, it is precisely paint coatings that are used to protect the metal surface from corrosion, since they are more affordable and easy to use. But such a layer needs to be updated every 5-7 years, which is laborious and costly. And using galvanic and electrochemical methods is too expensive, although rust can be forgotten for about 50 years.
That is why more and more anti-corrosion treatment of metal structures is carried out using "liquid rubber". This is a two-component material that is able to reliably and for a long time protect the surface from external influences. The use of an elastomer allows you to apply a seamless membrane layer, which is applied with a spray gun. Rubber quickly hardens on a surface, at the same time neither streaks, nor roughness are formed. Moreover, you can work even with a wet metal surface. Manufacturers of such funds say that such a coating can last about 20 years without losing its original properties.
Surface preparation
Reliable protection of the metal from rust can be achieved only if the surface has been prepared at the proper level. The equipment for anticorrosive treatment of metal structures itself is not difficult, so its use will not cause any problems. Surface preparation is carried out mechanically or chemically. Chemical methods are more popular, since mechanical methods cannot provide the proper level of protective equipment. But you need to choose the technology in accordance with the selected coatings and the conditions for their further operation.
Phosphating and chromating
Preparation of the metal surface is carried out depending on the type of metal. Surface preparation of ferrous metals is carried out using phosphating, and non-ferrous metals are processed by both methods. In general, the chemical preparation of a metal surface consists of several stages:
- surface degreasing;
- flushing with drinking water;
- applying a conversion layer;
- re-flushing with drinking water;
- rinsing with demineralized water;
- passivation.
Chemical treatment of metal is carried out by spraying (blasting at low pressure), immersion, steam-jet and hydro-jet methods. The first two methods involve the use of special aggregates that prepare the surface. The method is selected in accordance with the production program, configuration and dimensions of the products, and many other factors.
Piping Processing
Anticorrosion treatment of metal structures and pipelines is carried out in accordance with the requirements of state standards. Processing can be carried out both for a functioning pipeline, and during its reconstruction or repair. Pipelines can be protected by active and passive methods - it is selected in accordance with the laying method. For pipes laid above the ground, materials that are resistant to environmental influences are used. With the active method, a protective surface is created using substances that can provide electrochemical protection of the coating. Pipeline protection is carried out in several stages:
- First, the surface of the pipe gets rid of insulating coatings, rust, scale and all contaminants.
- Anticorrosive materials are applied to the cleaned surface, while work can be carried out at a temperature of +5 degrees and with a humidity of not more than 80%.
After treatment, the pipeline must be carefully inspected to identify defects if they are on the surface. Special instruments determine the quality of the connection between the surface and the coating, the quality of the coating itself and the thickness of the dry coating film.
Active and passive protection
Corrosion treatment of metal structures, the principle of which depends on the materials used, can be performed with active and passive surface protection. Both options are aimed at protecting metal pipes from harmful environmental factors. And if the water supply is located at great depths, there is a need to protect the metal from contact with the ground. Thanks to the protective layers of paint, varnish, enamel, a continuous and very strong barrier is created that protects the surface from the negative effects of the external environment.
Pipeline processing is often performed with powders based on plastic materials. They are applied to the pipe, which is preheated to a certain temperature.
Thus, anticorrosion treatment is an opportunity to prevent the appearance of rust on any metal surfaces. The variety of options and processing methods is the guarantee that you can protect anything - from pipes and a car to a small metal part.