S7 · Food-contact Stainless Steel
Food-Contact Stainless Steel (304/316L Media and Boundary List)
List the media, grades, and boundary conditions related to food-contact stainless steel according to a list of typical components and operating conditions: 4 typical parts/processes, including recommended grades, specifications, failure reasons, and standards.
Four Parts and Material List
| Part / Component | Recommended Grade | Size / Thickness | Surface | Main Failure Modes | Reference Standards |
|---|---|---|---|---|---|
| Cookware/Cups/Dishes/Insulated Cups | 304/316/201/430 | 3–1.2mm; Electrolysis/Glazing/2B | Cr≤0.25；Ni≤0.14；Mn≤2.0；Mo≤0.12；As≤0.002；Cd≤0.002；Pb≤0.01；Sb≤0.04mg/kg | Mn migration from 201 is higher than 304; Acidic food and high heat accelerate migration; Rough surface/Welding oxide increase migration | GB 4806.9—2023；GB 4806.1 |
| Sink/Tops/Kitchen Equipment Contact Surfaces | 304/316L | 8–3.0mm; 2B/Dull Finish/Raised Texture | Same as above | Cleaning agents/Food acids/Wear; Weld seams/hidden areas are double risks for migration and microorganisms | GB 4806.9—2023 |
| Commercial Kitchen/Air Scrubbers/Stools | 304 | Housing ≥1.2mm; Oil mesh ≥0.8mm | Contact surfaces follow GB 4806.9; Non-contact surfaces follow structure/fire resistance | Oil stains/High heat/Cleaning agents; Housing thinning sacrifices strength | GB 4806.9—2023；GB 50016 |
| Food Machinery/Pipes/Vessels/Pumps | 304/316L | Ra ≤0.8μm; Welded parts need passivation | Cr/Ni/Mn/Mo migration based on contact area/conditions | Welding HAZ can cause localized migration; CIP chemicals and residues add to the mix. | GB 4806.9—2023；GB 16798 |
Table showsStandard Configurations. The same part may switch from 304 to 316L or 2205 based on different media, temperatures, and welding methods—clearly stating usage conditions saves time.
Material Selection Tips
- The most common grades in this industry are 304 (4), 316L (2), and 316 (1)—parentheses indicate the number of affected areas. Use these as a starting point for quoting and material procurement.
- High-temperature sections add heat fatigue and oxidation; consider using 310S or heat-resistant castings (2/4 items hit).
- In acidic media, 316L is just the start; concentrations and temperatures rise to require 904L or duplex stainless steel (2/4 items hit).
- Thickness range: 0.3–3 mm—thin plates are formed parts (consider bending rebound and deep drawing cracks), thick plates are welded structures (consider heat input and sensitization).
Common Issues
Food-grade stainless steel: Which type of stainless steel is used most in GB 4806.9—2023 migration limits?
Based on the total list, the top three are 304 (4 items), 316L (2 items), and 316 (1 item). Specific to a part depends on media and temperature; for example, stainless countertops exposed to salt water should switch from 304 to 316L.
Which parts are most prone to issues?
Based on failure descriptions, typical examples include "kettles/tea cups/dishes/insulated cup liners"—201 has higher Mn migration risk than 304; acidic food and high temperatures accelerate migration; rough surfaces or weld oxide increase migration; recommended grades 304/316/201/430, specifications 0.3–1.2 mm; electrolysis/brushing/2B. For these conditions, specify media concentration, temperature, and cleaning methods in the design phase.
What thickness should be selected?
The listed thickness range is 0.3–3 mm—thin plates consider forming and surface properties, thick plates consider welding strength and structural integrity; different manufacturers may have varying values for the same part based on your drawings or operating conditions. Recheck these as needed.
Related Materials and Adjacent Industries
201Materials and Specifications304Materials and Specifications430Materials and Specifications316LMaterial and SpecificationsStainless Fasteners: A2-70/A4-70/A4-80/D Series and Latest StandardsStainless FastenersCarbon Steel Flanges for Seawater Desalination: 2205/2507 Pressure-Temperature-Corrosion BoundariesDuplex Flange & DesalinationSanitary Diaphragm Valves/Clean Valves: ASME BPE, Ra, and Temperature BoundariesSanitary Valves