How to select the appropriate sanitary-grade stainless steel pipe material based on specific require

The core logic behind choosing stainless steel pipes for hygiene purposes is "first match the core risks (corrosion, pressure) of the usage scenario, then balance cost and compliance". It can be carried out in four steps: "determine the corrosive environment → confirm the pressure and temperature → calculate the cost → verify compliance", ensuring that the material is perfectly suitable for the requirements. 

Step 1: Prioritize the assessment of "corrosive environment" - the core basis for material selection

Corrosion is the main cause of failure for sanitary pipes. It is necessary to determine the type of corrosion based on the medium that the pipe comes into contact with (food raw materials, cleaning agents, disinfectants). This directly corresponds to the material:

Scenario 1: Contact with ordinary weak acids and bases / water (without chloride ions)

Example media: Drinking water, milk, juice, beer, ordinary sugar solutions, cleaning agents are neutral or weakly alkaline (such as baking soda solution).

Core requirement: Basic corrosion resistance, no risk of chloride ion erosion.

Recommended material: 304 stainless steel. It has the highest cost-effectiveness and can meet the corrosion resistance requirements for such scenarios, and is easy to polish and meets basic hygiene standards.

Forbidden materials: There is no need to choose 316L or higher (cost waste), duplex steel has excessive strength. 

Scene 2: Contact with Chloride Ions / Moderately Corrosive Media

Media Examples: Seafood processing (salt water, seawater), pickled foods (high-salt soy sauce, vinegar), post-sterilization cleaning agents for dairy products (chlorine-based disinfectants such as sodium hypochlorite), acidic raw materials (citric acid, dilute phosphoric acid).

Core Requirements: Resistance to chloride point corrosion, resistance to moderately corrosive media.

Recommended Material: 316L Stainless Steel. Molybdenum can effectively inhibit the erosion of chloride ions on the pipe surface. The low-carbon design avoids intergranular corrosion after welding, making it the mainstream choice for the "corrosion-resistant upgrade version" in the food industry.

Forbidden Materials: 304 

Scene 3: Exposure to high-concentration corrosive media / extreme environments

Example of media: High-salt seasonings (pickled vegetable brine), food additives (weak hydrochloric acid, high-concentration citric acid), long-term exposure to strong oxidants (hydrogen peroxide solution).

Core requirement: Superb corrosion resistance, capable of withstanding high concentrations of chloride ions or moderately strong acids.

Recommended material: 317L stainless steel. The molybdenum content (3%-4%) is higher than that of 316L, making it more corrosion-resistant. It is only used in extreme corrosive scenarios (rarely used in ordinary food industries).

Alternative option: If there is also a need for high pressure, a molybdenum-containing duplex steel (such as 2507) can be selected, which combines corrosion resistance with high strength. 

Step 2: Confirm "Pressure + Temperature" - Eliminate performance shortcomings of materials

The mechanical strength and temperature tolerance range of different materials vary. It is necessary to select based on the working pressure and medium temperature of the pipeline:

High-pressure scenarios (working pressure > 1.6 MPa)

Application examples: High-pressure sterilization equipment pipelines (such as UHT ultra-high temperature instantaneous sterilization machines), high-pressure homogenizers connection pipes.

Core requirement: High strength, resistance to pressure deformation.

Recommended material: Duplex steel (such as 2205). The tensile strength (≈ 800 MPa) is more than 1.5 times that of 304/316L, the pressure resistance performance far exceeds austenitic stainless steel, and it can withstand chloride ion corrosion.

Forbidden material: 304/316L (insufficient strength, prone to creep or leakage in long-term high pressure).

Extremely high temperature scenarios

Low-temperature scenarios (medium temperature <-50℃): such as low-temperature brine pipelines in frozen food processing, recommended 304/316L (good low-temperature toughness), prohibited use of duplex steel (brittle fracture is prone at low temperatures).

High-temperature scenarios (medium temperature > 450℃): such as steam pipelines for high-temperature baking equipment, recommended 316L (higher stability at high temperatures than 304), avoid using 317L (significant decrease in high-temperature strength). 

Step 3: Calculate "Cost" - Avoid Over-Specification

The costs of different materials vary significantly. Under the premise of meeting performance requirements, costs should be controlled to avoid "choosing expensive but the wrong ones":

Cost ranking (from lowest to highest): 304 stainless steel

Cost balance principle:

For non-chlorine-containing and non-high-pressure scenarios, 304 is preferred (lowest cost, sufficient performance).

For chlorine-containing but not extreme scenarios, 316L is chosen (best cost performance, mainstay in the food industry for corrosion resistance).

Only for extreme corrosion scenarios (such as high-concentration hydrochloric acid) is 317L selected (to avoid an increase in cost of over 30% due to blind upgrading). 

Step 4: Verify "Compliance" - Ensure compliance with food industry standards

Food-grade pipes must be certified as food-contact materials to prevent heavy metals (such as lead and cadmium) from leaching into the food:

Core certification standards:

International standards: FDA (US Food and Drug Administration) certification, EU 10/2011 (EU Food Contact Materials Regulation).

Industry standards: 3A hygiene standards (for the dairy and beverage industries, with higher requirements for surface polishing and material purity).

Verification requirements: During procurement, suppliers are required to provide material reports (such as MTR material certificates), confirm material composition (such as the carbon content of 316L ≤ 0.03%) and certification documents, and avoid using "non-standard materials" (such as using 201 stainless steel to pass off as 304, which is prone to rust and has excessive manganese content).