The modern chemical industry is characterized by the intensive use of media with high corrosive activity — acids, bases, chlorides, oxidizing agents, organic solvents. The reliability and durability of process equipment directly depend on the correct choice of structural materials. Under such conditions, the use of corrosion-resistant steels is a prerequisite for ensuring industrial safety, minimizing operational risks and meeting standards.
What makes steel corrosion resistant
Before we move on to classification and applications, it's important to understand what kind of steel is becoming”stainless”.
The main mechanism of stability is the formation of a passivation film that protects the metal from destruction. This film is formed due to alloying elements, primarily chromium (Cr). When the chromium content exceeds 13%, a dense oxide film forms on the steel surface, which prevents further oxidation.
The main alloying elements are:
- Chrome (Cr) — the main element that forms a passive film.
- Nickel (Ni) — improves plasticity, corrosion resistance and resistance to low temperatures.
- Molybdenum (Mo) — increases resistance to pitting and crevice corrosion, especially in media containing chlorides.
- Manganese (Mn) — replaces nickel in economical brands, but reduces plasticity.
Why corrosion-resistant steels are important for the chemical industry
The use of corrosion-resistant steels in chemical production simultaneously solves several important problems:
- Protection from aggressive environments. Acids, bases, salts, and other chemicals destroy most common structural materials. Thanks to the addition of alloying elements, stainless steels make it possible to safely work with concentrated acids (hydrochloric, sulfuric, nitric), alkalis, ammonia, heavy metal salts, and organic solvents.
- Increasing the service life of equipment. Ordinary carbon steels break down in a matter of months. Stainless steels take several times longer. This is critical in a continuous production environment.
- Guaranteed safety and resiliency. Acid or alkali leakage due to corrosion can lead to fire, explosion, poisoning, and pollution. The use of stainless steels reduces the risk of accidents, protects staff and prevents environmental pollution.
- Lower costs. The higher cost of corrosion-resistant steels pays off due to increased equipment life and lower repair and replacement costs.
- Compliance with technical standards. Many industry regulations (GOST, ASTM, ISO) directly require the use of corrosion-resistant steels in corrosive environments.
Thus, the resistance of structural materials to chemical effects is becoming not just an advantage, but a necessity.
Basic requirements for materials in the chemical industry
To work successfully under chemical conditions, steels must simultaneously meet a number of requirements:
- Chemical and corrosion resistance. The material must retain its properties when in contact with acids, bases, salts and other active substances, as well as in mixed media at elevated temperature and pressure.
- Mechanical strength. The material must be strong enough to withstand increased pressure, vibration, dynamic and static loads, including shock, vibration and thermal effects.
- Chemical inertness. Steels for the chemical industry must be resistant to reactions with substances with which they come into contact. This is particularly important for preventing corrosion and material degradation.
- Heat resistance and heat resistance. Many processes in the chemical industry take place at temperatures above 400°C, which requires maintaining the properties of the material without structural degradation.
- Environmental safety. Materials should not release toxic components during use and disposal.
- Economic efficiency. When choosing a material, it is important to consider not only the purchase price, but also the total cost of ownership, including equipment life and maintenance costs.
These requirements form the criteria for selecting a specific steel grade for each process.
Types of corrosion-resistant steels and their characteristics
The variety of operating conditions has led to the creation of a large number of stainless steel grades that can be classified according to several criteria.
By structure:
- Austenitic steels — the most common and universal. They contain chromium (about 18%) and nickel (8 to 13%). They have high plasticity, strength, and excellent weldability. They are used in reactors, pipelines, valves, heat exchangers and vessels.
Examples: 12X18N9, 12X18H10T, 10X17N13M3T. - Martensitic steels — are characterized by high hardness, strength and wear resistance. They are used for the manufacture of cutting tools, elastic elements, fittings and other parts operating under high loads.
Example: 20X13. - Ferritic steels — cheaper than austenitic ones, but less resistant to acids. They are well welded and resistant to intergranular corrosion at moderate temperatures. They are used to make tanks, pipes, apparatus covers and other structures that are not subject to high mechanical loads.
- Two-phase (ferrite-martensitic) steels — combine the properties of ferritic and martensitic steels. They are used for the manufacture of equipment that requires high plasticity and strength, as well as increased corrosion resistance (for example, when working with chlorinated media).
For the main alloying elements:
- Chrome steels — they contain chromium as the main alloying element and provide protection against corrosion due to the formation of chromium oxide on the film surface.
- Chromium-nickel steels — the addition of nickel increases plasticity, resistance to shock loads and resistance to pitting corrosion.
- Chrome-manganese steels — economical option by replacing nickel with manganese. They are used where lower ductility and corrosion resistance are acceptable.
By appointment:
- Corrosion-resistant general-purpose steels — are used in various industries for the manufacture of parts operating in aggressive environments. For example, for pipes, vessels, fittings.
- Heat-resistant steel — are able to operate at high temperatures (above 600°C) while maintaining their structure and properties.
- Heat-resistant steels — retain mechanical properties during long-term operation at high temperatures.
The use of corrosion-resistant steels in the chemical industry
Each type of steel is used depending on operating conditions.
Austenitic steels
They are used for the production of equipment and pipelines that come into contact with aggressive chemicals, such as acids, bases and salts.
Examples:
- production of reactors, heat exchangers, tanks for storing and processing chemicals;
- manufacture of pipelines and other equipment for transporting acids and bases;
- creation of pumping system elements and valves with high corrosion resistance.
Brands: 12X18H10T, 10X17N13M3T — have excellent resistance to intergranular corrosion.
Martensitic steels
Suitable for use under high loads and wear due to their high strength and hardness. In the chemical industry, they are used for the manufacture of:
- cutting tools, pump blades, shafts and other products that require high strength;
- springs and other wearable parts operating under dynamic loads;
- items of equipment that are subject to high mechanical loads and must maintain their properties in constant contact with aggressive media.
Brand: 20X13 — widely used due to its hardness and wear resistance.
Ferritic steels
They are characterized by good weldability and high plasticity. They are used for the production of welded structures and vessels that are not subject to high mechanical loads.
Application examples:
- welded tanks for storing chemicals;
- pipelines and vessels for moderately aggressive media;
- equipment components for which high plasticity and corrosion resistance are important.
The effective operation of chemical plants in aggressive environments requires a systematic approach to the selection of materials based on computational and experimental data, standards and practical experience.
Corrosion-resistant materials produced by PZPS
The St. Petersburg Precision Alloy Plant offers a wide range of products productsthat meets the requirements of the chemical industry. The production line includes:
- Austenitic steels:
- 12X18N9 — general-purpose stainless steel;
- 12X18H10T — resistant to intergranular corrosion, used in welded structures;
- 10X17N13M3T — alloy with the addition molybdenum for working in particularly aggressive environments.
- Martensitic steel:
- 20X13 — an excellent combination of hardness and corrosion resistance, suitable for working under high loads.
- Special alloys:
- 40KHNM — precision alloy with specified elastic properties for parts with high requirements for accuracy and resistance to deformation;
- HN78T — heat-resistant nickel alloy that retains its properties at temperatures up to 1000°C.
PZPS produces products in the form of cold-rolled strip, which ensures high accuracy of geometry and uniform properties. To order products, please call +7 812 740-76-57 or leave application on the site. Our experts will contact you and help you select the material that meets your production requirements.
