One of the first choices you face when buying a stainless steel powder mixer is the material grade: AISI 304 or AISI 316? Both are stainless steels and cannot be told apart by eye. The difference between them becomes apparent when they come into contact with the product and with cleaning chemicals. In this article, we explain the difference between the two grades and which one is needed in which situation.
The Difference Between the Two Grades
AISI 304, containing approximately 18% chromium and 8% nickel, is the most widely used stainless steel grade in food and process equipment. AISI 316 additionally contains approximately 2–3% molybdenum. Molybdenum increases the steel's resistance to chlorides. Chlorides are found in salt and in chlorinated cleaning agents and can cause pitting corrosion in stainless steel.
| AISI 304 | AISI 316 | |
|---|---|---|
| Composition | Chromium and nickel | Chromium, nickel and molybdenum |
| Chloride and salt resistance | Moderate | Higher |
| Resistance to acidic products | Sufficient for most dry products | Higher |
| Cost | Lower | Higher |
The letter "L" (304L, 316L), often encountered in welded fabrication, denotes the low-carbon version. Low carbon helps preserve corrosion resistance in the weld zone.
Why Is Corrosion Less Common with Dry Powders?
Corrosion generally requires moisture. Completely dry powders put far less strain on the steel than liquid products. The risk increases when:
- The product absorbs moisture or liquids are added to the blend
- The product contains salt or other chlorides
- The product is acidic (for example, acidulants such as citric acid)
- The machine is wet-washed, especially with chlorinated cleaning agents
- Surfaces are not dried thoroughly after washing
When Is AISI 304 Sufficient?
AISI 304 is sufficient for most dry food powders such as sugar, flour, milk powder, protein powder, coffee and similar products. This is why, in our powder mixers, the body and product contact surfaces are made of AISI 304 stainless steel as standard.
When Should AISI 316 Be Preferred?
- Salty and chloride-containing products: salt, salted spice and seasoning blends, some mineral blends
- Corrosive chemicals: some detergent raw materials and powdered chemicals (Chemicals and Cleaning)
- Pharmaceutical-grade raw materials: where the customer or production specification calls for grade 316 (Pharmaceuticals)
- Intensive wet cleaning: where the machine is washed frequently and aggressive cleaning chemicals are used
In these cases, we manufacture our mixers from AISI 316 stainless steel on request.
Surface Finish Matters as Much as Material
The right steel grade alone is not enough. A rough surface retains product and moisture, becoming the point where corrosion and residue build-up begin. Polished, smooth interior product contact surfaces and properly finished welds both make cleaning easier and support the steel's corrosion resistance. For exterior surfaces, a polished or sandblasted finish can be chosen.
What to Ask When Buying
- What steel grade are the product contact surfaces made of?
- Are the parts other than the body (covers, shaft, discharge valve) of the same grade?
- How is the interior surface finished?
- Can a material certificate be provided?
You can browse all our models on the Powder Mixers page. If you share your product and cleaning method with us, we can assess together which grade is suitable.
