When choosing stainless steel for applications that require both corrosion resistance and non-magnetic behavior, engineers and designers often face the question: What is the best non-magnetic stainless steel?
Not all stainless steels are created equal — while most are resistant to rust and corrosion, only certain grades remain non-magnetic even after fabrication or cold working.
In this article, we will explore which stainless steel grades are truly non-magnetic, what makes them unique, and which one is the best choice for demanding industries such as marine engineering, medical equipment, food processing, and electronics. As a leading global supplier, SAKYSTEEL offers premium stainless steels that combine non-magnetic properties with superior mechanical performance.
Magnetism in stainless steel depends on its crystal structure, which determines how atoms are arranged and whether they can align under a magnetic field. There are three main structures:
Austenitic (Non-Magnetic) – Face-centered cubic (FCC) structure; stable, nonmagnetic even at low temperatures.
Ferritic (Magnetic) – Body-centered cubic (BCC) structure; naturally magnetic due to atomic alignment.
Martensitic (Magnetic) – Body-centered tetragonal (BCT) structure; hardenable and strongly magnetic.
Austenitic stainless steels are the only family of stainless steels that remain non-magnetic in their annealed condition, primarily due to their high nickel and chromium content.
The non-magnetic property in stainless steel arises from the austenitic phase stabilized by nickel. Nickel changes the internal lattice structure from body-centered cubic (BCC) to face-centered cubic (FCC), preventing magnetic domains from aligning.
The more nickel and nitrogen a steel contains, the more stable the austenitic structure becomes, which improves both non-magnetic performance and corrosion resistance.
For this reason, the best non-magnetic stainless steels generally have:
High nickel content (8% or more)
Moderate chromium (18% or higher)
Optional molybdenum or nitrogen to enhance corrosion resistance
The most widely used stainless steel in the world, 304 (UNS S30400) contains about 18% chromium and 8% nickel. It is non-magnetic in the annealed state but may develop slight magnetism after cold working or welding.
Applications: Kitchen equipment, tanks, food processing machinery, architectural panels.
Known as the “marine grade,” 316 (UNS S31600) contains 16–18% chromium, 10–14% nickel, and 2–3% molybdenum. The addition of molybdenum improves resistance to pitting and crevice corrosion in saltwater or acidic environments.
Applications: Marine hardware, chemical processing, medical instruments.
This high-temperature resistant alloy contains 25% chromium and 20% nickel. It remains non-magnetic and strong even in extreme heat environments.
Applications: Furnace parts, heat exchangers, and combustion chambers.
Stabilized with titanium, 321 stainless steel resists carbide precipitation during welding, maintaining non-magnetic behavior.
Applications: Aerospace, exhaust manifolds, and chemical processing.
A super austenitic grade containing high levels of nickel (24–26%), chromium (19–23%), and molybdenum (4–5%), with copper added for improved acid resistance. It is non-magnetic even after heavy cold work, making it one of the best choices for critical applications.
Applications: Offshore, petrochemical, pharmaceutical, and high-end industrial systems.
Among the various non-magnetic grades, 316L and 904L stand out as the best options when combining corrosion resistance, mechanical strength, and stable non-magnetic properties.
Low Carbon Content: Reduces carbide precipitation during welding, keeping it non-magnetic.
Outstanding Corrosion Resistance: Performs exceptionally in seawater and chloride environments.
Widely Available: Affordable and easy to machine, weld, and polish.
316L remains one of the most reliable non-magnetic stainless steels for industries that demand both hygiene and corrosion protection.
Super Austenitic Composition: 24–26% Ni, 4–5% Mo, and small additions of copper provide superior acid resistance.
Truly Non-Magnetic: Even after forming, bending, or welding, 904L retains its non-magnetic character.
Extremely Durable: Excellent resistance to sulfuric, phosphoric, and acetic acids.
High-End Applications: Used in chemical plants, marine engineering, and even luxury watchmaking due to its unique aesthetic and anti-magnetic properties.
In short, 316L is the best all-round non-magnetic stainless steel for general industrial and marine applications, while 904L is the best premium option for aggressive environments or precision applications where absolute non-magnetism is essential.
Non-magnetic stainless steels are used in industries where magnetism could interfere with performance or safety.
MRI scanners, surgical tools, and biomedical instruments use 316L and 904L because they don’t distort magnetic imaging or create electromagnetic interference.
316L and 904L perform exceptionally in saltwater conditions, making them ideal for shipbuilding, desalination plants, and subsea components.
Non-magnetic stainless steels prevent contamination, ensure hygiene, and resist acidic cleaning agents used in food production.
Non-magnetic materials prevent interference with sensitive sensors, navigation systems, and electronic circuits.
904L is preferred for tanks, pipes, and reactors exposed to strong acids, chlorides, and oxidizing agents.
| Grade | Composition Highlights | Corrosion Resistance | Magnetic Behavior | Typical Use |
|---|---|---|---|---|
| 304 | 18Cr–8Ni | Excellent | Nonmagnetic (may become slightly magnetic after cold work) | Food equipment, tanks |
| 316 / 316L | 16Cr–10Ni–2Mo | Superior (marine grade) | Nonmagnetic | Marine, medical, chemical |
| 321 | 17Cr–9Ni–Ti | Good at high temp | Nonmagnetic | Aerospace, exhaust |
| 310 | 25Cr–20Ni | Outstanding at high temp | Nonmagnetic | Furnaces, heaters |
| 904L | 20Cr–25Ni–5Mo–Cu | Exceptional (acid resistance) | Fully nonmagnetic | Offshore, chemical, luxury industries |
Even non-magnetic steels can exhibit weak magnetism under certain conditions. Common causes include:
Cold Working: Rolling, bending, or forming can induce a small amount of martensite.
Welding: Heat can create localized ferrite in the weld area.
Improper Alloy Balance: Low nickel content or high nitrogen may affect austenitic stability.
To minimize these effects, choose fully austenitic grades like 904L, and ensure proper annealing after fabrication.
A simple magnet test can help:
No attraction: Fully non-magnetic (austenitic)
Weak attraction: Slight cold work effect
Strong attraction: Magnetic (ferritic or martensitic)
For precise testing, magnetic permeability can be measured using a permeameter or magnetic susceptibility meter in laboratories.
SAKYSTEEL specializes in the production and export of high-grade stainless steels including 304, 316L, 321, and 904L. Our materials are widely used in marine, chemical, and medical industries worldwide.
Why customers choose us:
Guaranteed non-magnetic performance with certified testing.
All products supplied with EN 10204 3.1 / 3.2 certificates.
Compliance with ASTM, ASME, and ISO standards.
Global supply capability with fast delivery.
Professional technical support for alloy selection and fabrication guidance.
We deliver bars, plates, pipes, fittings, and customized shapes, all tested for mechanical properties, chemical composition, and magnetic response.
The best non-magnetic stainless steels are those that combine stable austenitic structure, excellent corrosion resistance, and mechanical reliability.
For most industrial applications, 316L stainless steel offers the perfect balance of affordability, corrosion resistance, and low magnetic permeability. For more demanding environments—such as chemical plants, offshore platforms, or luxury engineering—904L stainless steel is the premium choice, offering complete non-magnetic behavior and unmatched corrosion protection.
Whether you need marine-grade 316L or super austenitic 904L, SAKYSTEEL provides certified, high-quality stainless steel materials to meet your performance requirements with precision and reliability.