Stainless Steel: 304, 316 and 316L

The difference is molybdenum and carbon. It is invisible, so it has to be proven on paper.

DocumentTech Tuesday
SubjectStainless grades
Revision2026.1
First published4 August 2020
The stainless used in cannabis extraction is the same family used in pharmaceutical and food processing: austenitic stainless steel. Austenitic grades are non-magnetic and keep their crystal structure from cryogenic temperatures up to their melting point, so a column stays tough through chilling and recovery. Not every austenitic grade is the same, though, and the three you will see most are 304, 316 and 316L.

What is in them

All 300 series stainless contains high percentages of nickel and chromium. Nickel stabilizes the austenitic structure. Chromium protects the iron from oxidation, adds heat resistance and forms an invisible chromium-rich film that re-forms itself in the presence of oxygen. That film is what allows steam cleaning and fast sterilization without any coating.

Grade What sets it apart What it buys you
304 The baseline 18/8 chromium nickel grade Excellent general corrosion resistance, the standard for process equipment
316 Adds 2 to 3 percent molybdenum Resistance to chlorides, brines, sulfuric acid, iodides and fatty acids, and more heat resistance
316L 316 with low carbon, under 0.03 percent Less carbide formation at welds, so better corrosion resistance in the heat affected zone
You cannot see the difference. 304, 316 and 316L look identical. The grade is proven by a material test report (MTR) from a reputable supplier, traceable to the heat the material came from. On an ASME vessel that traceability is required.

Compatibility with extraction solvents

Solvent 304 316 / 316L
Butane, propane A A
Heptane, hexane A A
Ethanol, methanol A A
CO2 A A
Isopropyl alcohol B B
Pentane B B
Acetone A A

A: excellent. B: good, minor effect. Room temperature ratings, with the more conservative value printed where published charts disagree. In practice 304 and 316 are used with IPA and pentane across the industry. Full matrix in REF-CM-01 Chemical Compatibility.

The gaskets matter as much as the steel

  • Buna-N and Viton are compatible with butane, propane and heptane at room temperature.
  • On any joint that sees chiller or LCO2 temperatures, use PTFE. Hydrocarbon recovery runs to -65°C (-85°F), below the rating of Buna-N and Viton.
  • Clean gaskets with isopropyl alcohol. Never use acetone on Buna-N or Viton: acetone attacks both.

Sources. N.B. Oler Tech Tuesday, Stainless Steel: 304, 316 and 316L (2020). Thomas and Betts, 304 Stainless Steel Corrosion Compatibility Chart; Graco, Chemical Compatibility Guide (2013); Industrial Specialties Mfg., 316L Stainless Steel Compatibility Chart (2020). Ratings updated to N.B. Oler REF-CM-01, Rev. 2026.1.

Questions about your system? Call the shop at 541-330-6409, Monday to Thursday, 8 to 4 Pacific, or email info@nboler.com.
Back to blog