(760) 734-4177
304 Stainless Steel
Several types of stainless steel can be used to build packaging machinery. However, while there are global standards for stainless steel grades, the exact numbering and codes can vary by region. Keep this in mind as we discuss two types of stainless.
The most common form of 304 stainless steel is 18-8 (or 18/8), which contains 18 percent chromium and 8 percent nickel. 304 can withstand corrosion from most oxidizing acids, making it easy to sanitize and therefore ideal for kitchen and food-handling applications.
However, 304 stainless steel can still corrode in the presence of chloride solutions or saline food products. Chloride ions can create localized areas of corrosion, called “pitting,” which can spread beneath the protective chromium barrier. Solutions with as little as 25 ppm of sodium chloride can corrode stainless.
316 Stainless Steel
The second-most common form of stainless steel is 316 grade. It has nearly the same physical and mechanical properties as 304 stainless steel, but with slightly different chromium and nickel percentages.
316 stainless steel is about two to three percent molybdenum, which gives it its enhanced ability to resist corrosive saline environments and industrial solvents. Due to its non-reactive qualities, 316 stainless steel is also used in food handling and the manufacture of surgical instruments.
Then there is 316L stainless, the ‘L’ signifying a lower carbon content; the steel is composed of only .03% carbon, about the same as mild steel. This means that not only is it softer, but (per Bergsen Metals), it also has superior intergranular corrosion resistance.
This means that welds are less likely to decay than if you were to go with 316, and it is also less likely to corrode from corrosive chemicals. So 316L may be the safer bet if you need to weld stainless.
Which Steel Should I Use?
According to Sanitary Fittings, you should go with 316L if:
- Chloride exposure is likely
- Your system will see aggressive clean-in-place (CIP) cycles
- Weld density is high
- Your joint design is prone to crevices
- You’re writing specifications for audited environments
304 is better if you’re not submitting your machinery to as strenuous conditions (using low-chloride water, you have strong chemical dosing and rinse quality, etc.).
If you have any questions about these two types of steels and how they can be best utilized in a production environment, give Accutek Packaging a call. We’ll be happy to talk shop with you.
