A Stainless Steel Comparison – Grade 316 vs. Grade 304

All steels have the same basic iron and carbon composition, but stainless steel also contains a healthy dose of
chromium—the alloy that gives stainless steel its famous corrosion resistance. Stainless steel stains less easily than
other iron-based metals, but it’s not literally “stainless”. Just like standard steel, stainless can get marked up by
fingerprints and grease, develop discoloration, and eventually rust. The difference is resilience. Stainless steel can
withstand much more time and abuse before showing signs of wear.

Stainless steel must contain at least 10.5 percent chromium. Depending on the grade, it may contain much higher
chromium levels, and additional alloying ingredients. There are multiple grades under the stainless steel umbrella, each
with slightly different alloy composition, and therefore slightly different physical characteristics. Stainless steel types
include Ferritic, Austenitic, Martensitic, Duplex, and Precipitation Hardening (PH). A quick primer on the definitions of
stainless steel types can be found here.

The two most common austenitic stainless steel grades are 304 and 316. The key difference between stainless steel
grades 304 and 316 is the addition of molybdenum, an alloy that drastically enhances corrosion resistance, especially for
more saline or chloride-exposed environments. Commonly found in marine applications, 316 stainless steel contains 2
to 3% molybdenum, while 304 has none.

(Excerpts and content above from Reliance Foundry. “304 Stainless Steel versus 316 Stainless Steel”)

For pressure vessel components – our G-Series® & Mark VIII® Valves and all O-SEAL & Mark VIII® Fittings – CPV
Manufacturing uses austenitic grade 316/L SS as our standard offering. The 316 stainless steel we procure for our
fittings is dual certified to both 316 and 316L Grade. This dual certification ensures that the carbon content is 0.03% or
lower and the material has outstanding weldability.

Here’s a quick breakdown on the chemical composition, differentiating the two grades of stainless steel:

(Source: Australian Stainless Steel Development Association. “316: The First Step Up“)

(Source: Australian Stainless Steel Development Association. “304: The Place to Start“)

A few more key differences between these 304SS and 316SS include:
316/L stainless steel:

  •  Superior corrosion resistance
  • Chlorine resistant
  • Molybdenum content provides greater resistance to chemical attack than 304/L.
    • Is required for the manufacture of certain pharmaceuticals in order to avoid excessive metallic
      contamination, usually from manufacturing equipment.
  •  Considerably more resistant to solutions of sulfuric acid, chlorides, bromides, iodides and fatty acids at high
  • Common applications:
    •  Offshore, marine (especially with chlorides present) & washdown
    •  Chemical processing and storage equipment
    •  Refinery equipment
    •  Medical devices & pharmaceutical equipment
    •  Outdoor electrical enclosures
  •  UL Nema 4x rated & certified

304/L stainless steel (also known as 18-8 or 18/8):

  • Lowest Cost Corrosion Resistance Option
  • No limitations on fabrication
  • Resistant to oxidation
  • Common applications:
    • Auto moldings and trim
    • Wheel covers
    • Storage tanks
    • Kitchen equipment/appliances
    • Electrical enclosures
  • UL Nema 4x rated & certified

(Excerpts and content above from Nema Enclosures. “What’s the difference between 304 and 316 stainless steel?”)

CPV Manufacturing stocks all standard fittings in 316/L stainless steel because of its strength, enhanced corrosion
resistance and compatibility with various gases. Experience shows its superior functionality in a wide variety of critical
industrial applications and environmental conditions.

We can provide 304/L stainless components in certain applications if requested by the customer. However, 316/L is the
material of choice and is generally suitable for anywhere 304/L is used.

Please reach out to our Sales Team here for further information and quote requests. Our Engineering team can answer
any technical questions you may have as well!

Additional Sources used for this article: