What are the differences in application scenarios between different types of sanitary-grade stainles

The selection of the material for sanitary-grade stainless steel pipes is closely related to the compatibility of the application scenarios. Different materials exhibit significant differences in actual applications due to variations in chemical composition, mechanical properties, and corrosion resistance. The following provides a detailed analysis from common material types, performance differences, and specific application scenarios: 

I. Common Types and Characteristics of Hygienic Stainless Steel Pipes

1. 304 (06Cr19Ni10) Stainless Steel

Chemical composition: Contains approximately 18-20% Cr, 8-10.5% Ni, with a carbon content of ≤ 0.08%.

Performance characteristics:

Corrosion resistance: Has good corrosion resistance to atmospheric, water, weak acids / bases, etc., but has relatively weak resistance to chloride ions (such as salt water, seawater) corrosion.

Strength and machinability: Moderate strength, easy welding and forming, good surface treatment (such as polishing, electrolysis) effect.

High-temperature resistance: Can be used for long-term operation within the range of -196℃ to 800℃.

Typical application scenarios:

Food and beverage industry: Milk pipelines, beer brewing equipment, juice transportation pipelines (medium corrosivity, must meet hygiene standards).

General water treatment: Pure water transportation, municipal drinking water pipelines (no strong corrosivity of water quality).

Light industry: Material transportation pipelines in cosmetics and health products production.

2. 316L (022Cr17Ni12Mo2) Stainless Steel

Chemical composition: Contains approximately 16-18% Cr, 10-14% Ni, 2-3% Mo, with a carbon content of ≤ 0.03% (low carbon type).

Performance characteristics:

Corrosion resistance: Due to the addition of molybdenum, the resistance to chloride ion corrosion is significantly better than 304, especially resistant to sulfuric acid, hydrochloric acid, seawater and halide medium corrosion.

High-temperature resistance and intergranular corrosion resistance: The low carbon content reduces the risk of intergranular corrosion, suitable for high-temperature (such as steam sterilization) environments.

Hygiene performance: The surface passivation film is more stable, less prone to bacterial growth, meeting GMP (Good Manufacturing Practice) requirements.

Typical application scenarios:

Pharmaceutical and medical industry: Injection production lines, sterile pure water systems (must withstand acid-base cleaning solutions and high-temperature sterilization).

Chemical and marine environment: Transportation of chlorine ion-containing chemical materials (such as bleach, dye solutions), seawater desalination pipelines in marine engineering.

Food processing: High-salt, high-acid foods (such as soy sauce, pickles) storage and transportation equipment.

3. 317L (022Cr19Ni13Mo3) Stainless Steel

Chemical composition: Contains approximately 18-20% Cr, 11-15% Ni, 3-4% Mo, with a carbon content of ≤ 0.03%.

Performance characteristics:

Corrosion resistance: The molybdenum content is higher than 316L, stronger resistance to pitting and crevice corrosion, suitable for more demanding acidic or chloride environments.

Strength and temperature resistance: Higher high-temperature strength than 316L, can be used for long-term operation at higher temperatures (such as below 1000℃).

Typical application scenarios:

High-corrosion chemical fields: Transportation of strong corrosive media such as concentrated nitric acid, formic acid, acetic acid.

Environmental protection equipment: Acidic waste gas treatment pipelines in waste incineration plants, high-salt wastewater pipelines in sewage treatment.

Marine engineering: Deep-sea equipment, ship seawater cooling systems (resistant to long-term erosion by seawater).

4. 904L (015Cr21Ni26Mo5Cu2) Stainless Steel

Chemical composition: Contains approximately 20-22% Cr, 23-25% Ni, 4-5% Mo, 1.0-2.0% Cu, with a carbon content of ≤ 0.02%.

Performance characteristics:

Super corrosion resistance: Extremely strong corrosion resistance to non-oxidizing acids such as sulfuric acid, phosphoric acid, hydrochloric acid.

Stress corrosion resistance: Outstanding resistance to stress corrosion cracking in chloride and sulfide environments.

High cost: Due to high nickel and molybdenum content, the price is approximately 3-5 times that of 304.

Typical application scenarios:

Extreme corrosive environments: Crude oil desulfurization devices in petrochemicals, sulfur production equipment, pipelines in wet metallurgy. Special scenarios for food and pharmaceuticals: High-end equipment that comes into contact with high concentrations of organic acids (such as citric acid, lactic acid).

5. Duplex stainless steel (such as 2205, 2507)

Chemical composition: Taking 2205 as an example, it contains approximately 22% Cr, about 5.5-6.5% Ni, and about 3-3.5% Mo. It has both austenitic and ferritic structures.

Performance features:

High strength and corrosion resistance: The strength is more than twice that of 304, the chloride ion corrosion resistance is close to that of 316L, and the stress corrosion resistance is excellent.

Temperature resistance: Suitable for the range of -50°C to 250°C. Good toughness at low temperatures.

Typical application scenarios:

High-pressure equipment: Chemical pressure vessels, high-pressure pipelines on offshore platforms (must meet both strength and corrosion resistance).

Seawater treatment: Seawater heat exchangers, sewage treatment equipment in coastal areas.

6. 430 (10Cr17) stainless steel (ferritic)

Chemical composition: Contains approximately 16-18% Cr, no Ni, and carbon content ≤ 0.12%.

Performance features:

Corrosion resistance: Better than carbon steel, but not as good as austenitic stainless steel (such as 304), with poor intergranular corrosion resistance.

Low cost: The price is approximately 50-60% of 304. Strong magnetic property, general processing performance.

Typical application scenarios:

Low corrosion scenarios: Enclosures of equipment not in direct contact with food, kitchen appliances (such as sinks).

Cost-sensitive industries: Ordinary industrial pipelines (mediums without strong corrosivity and lower hygiene requirements). 

II. Comparison Table of Application Scenarios for Different Materials

Picture 1 

III. Core Influencing Factors for Material Selection

1. Material Properties:

Chloride ion concentration: 316L is suitable for chloride ion concentrations ≤ 1000 ppm, while 317L/904L is suitable for higher concentrations (such as seawater > 20000 ppm).

Acidity and Alkalinity: 304 is suitable for neutral/weakly acidic/alkaline conditions, 316L for medium acidity/alkalinity, and 904L for strong acidity/alkalinity.

2. Temperature and Pressure:

High-temperature environments (such as steam sterilization) prefer 316L/317L; high-pressure scenarios choose duplex steel.

3. Hygiene Standards:

Pharmaceutical and medical applications must comply with GMP/ISO 13485; 316L is preferred (as the surface passivation film is more stable).

4. Cost and Economy:

For ordinary food and beverages, 304 is selected; in high-corrosion scenarios, performance and cost are balanced (such as 316L vs 904L). 

IV. Case Analysis

Case 1: Dairy Production Line

The milk conveying pipeline usually uses 304 material because milk has a pH close to neutrality, with low corrosivity, and the surface of 304 is easy to clean after polishing, meeting food contact standards (such as FDA). If high-salt cheese processing is involved, 316L must be upgraded to resist salt corrosion.

Case 2: Anti-tumor Drug Production

During the drug synthesis process, strong corrosive reagents such as hydrochloric acid and sulfuric acid may be used, and frequent high-temperature sterilization (121℃ steam) is required. At this time, 316L or higher specification materials must be selected to avoid pipeline corrosion leading to medium contamination.

Case 3: Seawater Desalination Project

Seawater contains high concentrations of chloride ions (approximately 20,000-30,000 ppm). Ordinary 316L may suffer pitting corrosion, so 904L or duplex steel 2507 must be selected to ensure long-term resistance to seawater erosion of the pipeline. 

Summary

The selection of material for sanitary-grade stainless steel pipes is a balance between performance, cost and the requirements of the application scenario: 304 is the entry-level material that covers most low-corrosion scenarios; 316L is the "standard configuration" for industries such as pharmaceuticals and healthcare; 317L/904L and other high-end materials are used in extreme corrosive environments; duplex steel achieves the optimal solution between strength and corrosion resistance. In practical applications, it is necessary to comprehensively consider the medium composition, temperature, pressure and hygiene regulations to ensure the safety and economy of the pipeline system.