Some stainless steel is magnetic and some is not. The common austenitic grades, 304 and 316, are essentially non-magnetic when annealed, while ferritic, martensitic and duplex stainless steels are strongly attracted to a magnet.
To complicate things, 304 can become noticeably magnetic after it is bent, rolled or drawn, and welds in non-magnetic grades can pull slightly on a magnet. This guide explains why, which grades do what, and why a magnet is a poor way to judge the quality or grade of stainless steel.
Why Some Stainless Steel Is Magnetic
Whether a steel sticks to a magnet depends on its crystal structure, not just on how much iron it contains. All stainless steels are mostly iron, with at least 10.5 percent chromium for corrosion resistance. Iron at room temperature normally has a structure called ferrite, which is strongly magnetic. That is why ordinary carbon steel, covered in our what is steel made of guide, sticks to a magnet.
Adding enough nickel (and some manganese or nitrogen) changes the structure to austenite, which is not magnetic. So the stainless families split by structure:
- Austenitic (300 series such as 304 and 316): austenite structure, non-magnetic when annealed.
- Ferritic (such as 409 and 430): ferrite structure, magnetic.
- Martensitic (such as 410 and 420): martensite structure, magnetic, and hardenable by heat treatment.
- Duplex (such as 2205): roughly half austenite and half ferrite, magnetic.
Is 304 Stainless Steel Magnetic?
Annealed 304 is not attracted significantly by a magnet. Cold-worked 304 can be. The Australian Stainless Steel Development Association explains in its Technical FAQ 3: Magnetic Effects of Stainless Steels (checked October 2026) that cold deformation turns some of the austenite into martensite, which is magnetic. ASSDA says the effect is most often noticed in heavily cold-worked items such as wire or the dished end of a pressure vessel, and that the martensite can become magnetized enough to pick up light objects like paper clips.
That is why the bent corners of a 304 sink, a cold-formed tube or a coil of 304 wire may grab a magnet while the flat areas barely react. It does not mean the steel is a different grade.
Is 316 Stainless Steel Magnetic?
Annealed 316 is non-magnetic and usually stays less responsive than 304 after cold work. ASSDA notes that the effect is weaker in alloys with more austenite stabilizers such as nickel, nitrogen and carbon, and 316 has more nickel than 304. It also states that highly alloyed austenitic grades, including the high-nitrogen grades, do not form martensite on cold work and keep a relative permeability below 1.02.
Magnetic Response by Stainless Steel Grade
The table summarizes the grades you are most likely to meet. Sources are ASSDA FAQ 3 and the worldstainless Stainless Steel Grade Sheets (checked October 2026).
| Grade | Family | Annealed | After cold work |
|---|---|---|---|
| 301 | Austenitic | Non-magnetic | Strongly attracted to a magnet |
| 304 / 304L | Austenitic | Non-magnetic | Can become noticeably magnetic |
| 316 / 316L | Austenitic | Non-magnetic | Less effect than 304 |
| 302HQ | Austenitic | Non-magnetic | Stays essentially non-responsive |
| 904L | Austenitic | Non-magnetic | Non-magnetic in all conditions |
| 409, 430 | Ferritic | Strongly magnetic | Strongly magnetic |
| 410, 420 | Martensitic | Strongly magnetic | Strongly magnetic |
| 2205 | Duplex | Strongly magnetic | Strongly magnetic |
For scale, ASSDA gives the relative permeability of mild or carbon steel as at least 200, where 1 is the value for air. Annealed austenitic stainless sits very close to 1, which is why a magnet barely notices it.
Welds, Castings and Heat Damage
Welds
Welds in 304 and 316 are usually designed to contain a few percent ferrite, because a little ferrite stops hot cracking as the weld cools. ASSDA notes that this makes the weld weakly magnetic, but the effect is usually insignificant because welds are a small part of the structure. Our welding stainless steel guide covers filler choice and heat control.
Castings
Cast austenitic stainless parts, such as valve and pump bodies, typically carry a few percent ferrite and are weakly attracted to a magnet, even though the matching wrought grade is not.
Sensitization
Poor heat treatment or high heat input welding of normal-carbon austenitic grades can form chromium carbides at the grain boundaries. ASSDA explains that this lowers corrosion resistance and can form magnetic martensite around the carbides. In this case a magnetic response near a weld can be a warning sign rather than a harmless quirk.
Can You Use a Magnet to Test Stainless Steel?
Only in a very rough way. A magnet can suggest whether a part is likely austenitic or one of the magnetic families, but it cannot reliably tell 304 from 316, because both are non-magnetic when annealed and both can gain some attraction from forming. It also cannot judge corrosion resistance: ferritic and duplex stainless steels are genuine stainless steels and are strongly magnetic. Duplex grades are often chosen for corrosive service.
When the grade matters, for example for marine hardware, food equipment or structural parts, rely on the mill certificate or a proper chemical analysis such as a handheld XRF test, not a fridge magnet.
Why Magnetism Matters in Practice
- Equipment near sensitive instruments. Parts used near magnetically sensitive equipment are often specified in low-permeability austenitic grades, and heavily cold-worked 304 may not meet a permeability limit.
- Magnetic separators and food lines. Plants that use magnets to catch tramp iron need to know which stainless parts the magnets will also pull on.
- Fixing and handling. Magnetic lifters, magnetic drill bases and magnetic tool holders grip ferritic, martensitic and duplex stainless, but not annealed 304 or 316.
- Choosing against galvanized steel. If you are deciding between coatings and alloys, our galvanized vs stainless steel comparison covers corrosion and cost, and is galvanized steel magnetic explains why zinc-coated steel always sticks.
For sizes of stainless tube in 304 and 316, see the stainless steel tube sizes chart.
Is Stainless Steel Magnetic? FAQ
Does a magnet stick to real stainless steel?
It can. Ferritic grades like 430, martensitic grades like 420 and duplex grades like 2205 are all real stainless steels and are strongly magnetic. Only austenitic grades like 304 and 316 are non-magnetic when annealed.
Why is my 304 stainless steel magnetic?
Most likely because it has been cold worked by bending, rolling, drawing or forming, which turns some austenite into magnetic martensite. Welds can also be slightly magnetic because they are made with a little ferrite on purpose.
Is magnetic stainless steel lower quality?
Not by itself. Magnetism reflects structure, not quality. A ferritic grade has different corrosion resistance than 304, and the right choice depends on the environment, but being magnetic does not make a steel fake or inferior.
Can you make magnetic 304 non-magnetic again?
Yes, by solution annealing and water quenching. ASSDA notes this also reduces the strength gained from cold work and can cause distortion, so it is only done when low magnetism is required.
Which stainless steel is completely non-magnetic?
Highly alloyed austenitic grades stay closest. The grade sheets describe 904L as non-magnetic in all conditions and 302HQ as essentially non-responsive even after substantial cold work, and ASSDA notes high-nitrogen austenitics stay below a relative permeability of 1.02.
Reference information only, not engineering advice. Disclaimer.