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: 4 typical components/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/knives/dishes/insulated cups inner walls | 304/316/201/430 | 3–1.2mm; electrolysis/polishing/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 | Manganese migration from 201 is higher than from 304; acidic food and high temperature accelerate migration; rough surface/welding oxide increase migration | GB 4806.9—2023；GB 4806.1 |
| Sink/countertops/kitchen equipment contact surfaces | 304/316L | 8–3.0mm; 2B/satin/rubbed | Same as above | Cleaning agents/food acids/wear; welds/grooves are double risk for migration and microorganisms | GB 4806.9—2023 |
| Commercial kitchens/smoke hoods/workbenches | 304 | Hood body ≥1.2mm; oil mesh ≥0.8mm | Contact surfaces follow GB 4806.9; non-contact surfaces follow structure/fire resistance | Oil stains/high temperature/cleaning agents; thinning of hood bodies sacrifices strength | GB 4806.9—2023；GB 50016 |
| Food machinery/pipes/valves/pumps | 304/316L | Ra ≤0.8μm; welding pieces need to be passivated | Cr/Ni/Mn/Mo migration follows contact area/conditions | Welding HAZ can cause localized migration; CIP chemicals and residues add to the mix. | GB 4806.9—2023；GB 16798 |
In the table arestandard 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 without specifying grades directly.
Key considerations in material selection
- The most common grades here are 304 (4), 316L (2), and 316 (1)—parentheses indicate the number of affected areas. Use this as a starting point for quoting and material preparation.
- At high temperatures, consider heat fatigue and oxidation; if necessary, use 310S or heat-resistant castings (2/4 items hit).
- In acidic media, 316L is just a baseline; higher concentrations and temperatures 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 for migration limits in GB 4806.9—2023?
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 the medium and temperature; for example, stainless countertops exposed to salt water should switch from 304 to 316L.
What parts are most prone to problems?
Based on failure descriptions, typical issues include "kettles/ cups/wares/insulated cup liners": Manganese migration in 201 is higher than in 304; acidic food and high temperatures accelerate migration; rough surfaces or welding oxide increase migration; recommended grades 304/316/201/430, thickness range 0.3–1.2 mm; electrolysis/ polishing/ 2B. For these conditions, specify the medium concentration, temperature, and cleaning method in design.
What thickness should be chosen?
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. Revalidate with your specific situation.
Related Materials and Adjacent Industries
201Materials and Specifications304Materials and Specifications430Materials and Specifications316LMaterials and SpecificationsStainless Fasteners: A2-70/A4-70/A4-80/D Series and Latest StandardsStainless FastenersWeld Neck Flanges for Seawater Desalination: 2205/2507 Pressure-Temperature-Corrosion BoundariesDuplex Flange & DesalinationHygienic Diaphragm Valves/Clean Valves: ASME BPE, Ra, and Temperature BoundariesSanitary Valves