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"How to test which type of stainless steel we have"


Q. Dear Sir/ Madam
We are a Trading Company based in China. We trade Automobile Parts and Accessories. We also export Hose Clamps made from different types of materials like Carbon Steel, SS 301, SS410 etc. But these days we face problems regarding the quality of material. Like the companies in China send the material as Stainless Steel but it comes out to be Carbon Steel. We know one property to differentiate between Carbon Steel and Stainless Steel i.e. Magnetism, the Carbon Steel will attract to magnet but Stainless Steel wont. But we face another problem that our supplier says that Clamp is made of SS 410 but it is attracting the magnet and the reason provided by the factory is that they have not removed the magnetism. So, we are confused whether the material is really SS 410 or its still Carbon Steel. Is there any simple possible way by which we can check the quality of the materials and differentiate between Carbon Steel, SS 301 and SS 410. As I was reading an article published by you where its mentioned that we can perform a Boiling Water or Salt Water Test. I would like to know more about the tests so that we can avoid the problem.

Hope to hear from you in a positive response.

Thanks in advance.

Best regards,

Bhavneet Singh
Automobile Parts and Accessories Trading Company - Shanghai, China

"Stainless Steels: An Introduction and Their Recent Developments"

from Abe Books

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A. If this is as frequent and serious problem as it sounds to be, you could invest in a "Scrap Sorter" hand-held X-ray fluorescence machine. It will almost instantly identify the alloy.

But you must also institute a certification program where the seller promises in writing what the material is with every shipment. And then you have to blacklist any seller who proves to be a problem.

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey


A. I use the copper sulfate test as a first level sorting, often with good results. Dissolve about 8 grams of copper sulfate in about 500 ml of water. Swab that onto your part. Carbon steel surfaces will immediately show a copper color as the iron dissolves and the copper replaces it. 300 series stainless shows no reaction, and 400 series USUALLY won't show a reaction, or it'll be very limited.

I don't use the variation of copper sulfate solution that contains 2 to 3 ml of sulfuric acid, as I consider that too aggressive for the 400 series stainless.

Realize that your results may vary depending on how clean your surface is, or if it is contaminated by embedded iron particulate, sometimes found on non-passivated stainless steels. Take a look at Method 102 in Mil-STD-753 [link is to free spec at Defense Logistics Agency, dla.mil] which you can find on Assist Quicksearch [Ed. note: replaced by AMS-STD-753 [affil. link to spec at Techstreet]].

lee gearhart
Lee Gearhart
metallurgist - E. Aurora, New York


Q. Hello Ted & Lee,

Any idea as to why the copper sulfate replaces the iron with copper in carbon steel but not the iron in most stainless steels?


Chris Pierce
- Troy, Ohio


A. Hi Chris!

For the same reason that stainless steel is stainless. The chromium oxide layer at the surface renders the surface passive, and protects the metal.

lee gearhart
Lee Gearhart
metallurgist - E. Aurora, New York

January 5, 2010

A. Hi

I found this link and thought it might be helpful for You for quick stainless steel assessment:



Sebastian Jurek
- Newbridge, Ireland

November 21, 2011

A. The only stainless steel that is not attracted by magnet is austenitic grade: 304,316, 201,202. The others such as 400 series are magnetic. However, some austenitic grade could become magnetic when cold worked, especially 304.

I own a nickel and molybdenum test kit. This test kit is actually created to differentiate 304 and 316. however as I am kind of curious guy, I have tried it on several samples: carbon steel, series 200, and of course 400 series.

I purchased it from an Indonesian company. www.agp-supply.com

here is a link to their demo video :

Here are my results:
carbon steel: Ni test show no reaction at all
Series 200: Ni test show dark brown color whereas for 300 series it should be yellow
Series 400: Ni test show positive result by showing yellow color

So you could use this test kit to sort carbon steel and 200 series. For 400 series you could easily use magnet as they are supposed to be magnetic.

In southeast asia, I never worried about supplier selling carbon steel as stainless steel as uncoated carbon steel rusts easily within a matter of days. It is more common for supplier to fake series 300 by supplying 200 series which is much cheaper.

Benny H [last name deleted for privacy by Editor]
- Surabaya, Indonesia

March 28, 2012 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. How is the grade of ss confirmed whether 202 or 304?

- Chennai, Tamilnadu, India

May 26, 2014

Q. 1. Chemical Test to test the grade of Stainless steel.

2. More information on Battery test to confirm the grade of Stainless Steel: What is the equipment, What are the chemicals used?

3. Any other non destructive , simple and non expensive Test to differentiate between 200, 300, & 400 series of Stainless Steel

Naval Pestonjee
- Pune, Maharashtra India

"Stainless Steel for Design Engineers"

from Abe Books or

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May 2014

A. Hi Naval. If there were a non-destructive AND simple AND non-expensive test that was accurate, we wouldn't need any others. Magnetic tests meet all three requirements, but don't tell you very much. So please keep in mind the aphorism "Two out of three ain't bad" :-)

a.) Non-destructive and simple is the x-ray fluorescence "scrap sorters" previously mentioned, but it's capital intensive (expensive).
b.) Non-destructive and non-expensive might be very carefully controlled spot tests and electrochemical tests such as the molybdenum spot test previously mentioned and the electrochemical tests available per the banner ad at the bottom of the page (not necessarily simple, and may involve careful tracking, and substituting test samples in lieu of your fabricated parts)
c). Simple and non-expensive include spot tests, spark tests, etc. But they may be destructive.

Describing all practical tests for differentiating every possible type of stainless steel would takes a good-sized book rather than a forum posting. If you can be more specific with your question, readers can probably be more specific with answers. Good luck!


Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

December 29, 2014

Q. How can you tell what type of 400 series stainless steel it is W/ no MTR and all it says on the box it came with only says 400 series?
Trying to find out so I can use the proper Welding Procedure.

Phil Baron
- Edmonton, Alberta, Canada

December 2014

A. Hi Phil. Although people refer to a 400 or 4xx "series" of stainless steels, my understanding is that there is a "type 400" stainless steel. Are you sure the box says "400 series" rather than "type 400"? If the box says "type 400" it doesn't mean it might be 409 or 410 or whatever, it means it's 400.


Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

February 27, 2015

Q. A while back I made some knife blanks. I can't remember if I used 440C or ATS34. These are the only two knife steels I have used. I soon will have these knife blanks ready to out to be Heat Treated. I'm not sure what to do here. Is there a way to determine which one of these two stainless steels I have? Any help would be appreciated.


Paul Rousseau
Hobbyist - Orlando, Florida usa

February 2015

A. Hi Paul. According to the composition charts, ATS34 seems to have 5X as much molybdenum as 440C. It may be possible to do a molybdenum test. Koslow Scientific Testing Instruments [a finishing.com supporting advertiser] may be able to help.


Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

August 29, 2016 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Dear Sir,

I am planning to install outdoor SS railing for which I went for a market survey. During the conversation with a dealer, I was informed that 304 is the best quality for the outdoor applications. Then I wanted to how to distinguish 304 from 202 to avoid any sort of cheating. The dealer then took a small bottle containing some chemical. He put a drop on each of the two different SS pipes. In one pipe, the colour changes to reddish on the particular portion where he dropped the chemical. On the other hand, there was no change in colour in the second pipe. Then he tried to convince me that the pipe where colour changed is made of 202 and the second one is made of 304.

Therefore, I would like to know the authenticity of his experiment to distinguish between 202 & 304.


Indrajit Talukdar
- Guwahati, Assam, India

August 2016

A. Hi Indrajit. We appended your inquiry to one of many threads on stainless steel testing. Yes, there are spot tests to determine certain characteristics of stainless steel, including composition and whether or not it has been passivated. But it is probably difficult for people to guess what chemical the dealer used and whether it actually revealed passivation vs. composition, let alone type 202 vs. type 304. Spot tests can be valid, but I don't know whether this particular one was. You might contact a supplier of such spot tests, like Koslow Scientific Testing Instruments [a finishing.com supporting advertiser], and see if you can get the test solutions and procedures yourself. Good luck.


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

September 13, 2016

A. One of the common ones is a spot test for molybdenum, used to attempt to determine moly containing grades (e.g. 316) from non-moly containing grades (e.g. 304).

The only real foolproof method is to send a sample to a lab for analysis or have one of those very expensive handheld XRF units.

If the suppliers involved are reputable, typically just a material cert sheet is deemed sufficient.

ray kremer
Ray Kremer
Stellar Solutions, Inc.
supporting advertiser
McHenry, Illinois
stellar solutions banner

adv.    koslow 316 stainless steel test kit

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