Letter 6060

Test for difference between 316 and 304

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I have about £1000 worth of perforated stainless steel sheets. The problem is that they are a mix of 304 and 316. There is a test that i know of. A chemical is applied to 316. It tests for the 'molyb-da-mum' (that's rougly how it's pronouced but i'm sure that it's not it's most accurate spelling) content in the 316. The chemical is green and turns brown when it reacts with the M word in the 316. As 304 does not contain any, the chemical stays green. My problem is i cannot remember the name of the chemical. ... Please help.

Ziya Ahmad
perforators - West Midlands, England

According to ASTM STP 550, possibly available from the ASTM, the test for molybdenum in 300 series stainless is to

a) Place equal drops of concentrated hydrochloric acid and concentrated nitric acid on the metal surface. Allow 3 to 4 minutes for reaction and transfer 2 drops to a spot plate.

b) Add 2 drops of 10% potassion thiocyanate.

c) Add 25% sodium thiosulfate dropwise stirring until the red color begins to disappear. A violet color will appear if molybdenum is present.

However, I think your best course of action is to get a chemical spot test kit form Koslow or Systems Scientific Labs or some other company that makes them. A quick web search under "chemical spot test" should show manufacturers if they foolishly aren't already listed on finishing.com, and I know the two mentioned above offer small kits just for 304 vs. 316 resolution. Good luck!

Lee Gearhart
- East Aurora, NY, USA

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Aww, shucks, you're just trying to embarass us :-), but thanks! - finishing.com

Ziya,

Surely you can get the name of the 'green' chemical for identifying molybdenum somewhere in a local city. Try first a major supplier of chemicals and ask to speak to the lab technician first of all!

Failing that, contact a major supplier of stainless. OK? There's Henry Wiggin, too. Highly competent Company but speciallizing in the ultra high Ni.Mo alloys.

Mind you, had you a 'magnetometer' I'd guess that 3l6 would show a lower reading than 304. But that's pretty esoteric. Stainless does, yes, DOES contain some magnetism albeit of a low order.

Cheers !

Freeman Newton - White Rock, B.C. Canada

How can I check difference in between 304-316 and 202? Please advise.

Harvinder
-Delhi, India

Hello i have the answer for you i think over here it's named CELMO MOLIBDENIUM REAGENT We are testing lot's of 4301 and 4401 materials and have bought a small electrical tester MOLYTESTER. Look for corrocean I Hope you can use this information. Good Luck !!

Johan Faber
steel trader - Almere (Holland)

We have a few SS316 materials fabricated and machined. There is no scope for cutting a sample to check the chemical composition. Also we are not in a position to go for handheld tester to test these materials as they are simply not available at the place of material. Is there any other method by which I can check the material.

Thanks,

Suni lKhanna
pharmaceuticals - Indore, India

i know of a way to tell the differance tween 304 and 316. this method has been used in recycling for years. its called "spark test" . with an angle grinder grind 304 look at sparks they will fork out at the end of they're flight. 316 will spark but each spark will stay intact till the end of its flight. try it out its cheap and better for the enviroment.

Bill Rucinski
- Hatley Wisconsin

I am into the construction and interiors line and have a problem: how would we be able to check to see if a kitchen basket of stainless steel is made of 202 or 304 SS? (If possible, some way where even a lay-man could check for him / herself) There are just too many instances of customers being taken for a ride. Thanks!

Kiran Khambadkone
construction / interiors - Mangalore, Karnataka, India

DEAR SIR
WE ARE LOOKING FOR THE CHEMICAL TO DETECTION OF MOLYBDENUM IN STAINLESS STEEL . WE HAVE FOUND SOME COMPANY SELL TOTAL KIT BUT WE NEED ONLY THE CHEMICAL. DOES IT CALLED ELECTROLYTE?
WE WOULD BE GREATFULL IF ANYONE ADVICE WHAT IS THE EXACT COMMERCIAL NAME OF THAT CHEMICAL TO FIND.
IT WOULD BE BETTER IF WE GET IN INDIA.
MOSTAFIZ

MOSTAFIZ
BUYER - CHITTAGONG, BANGLADESH

I believe that Lee Gearhart's initial response answers your question, Mostafiz. However, I am not able to source the ASTM SP550 spec he mentions. Good luck.

Ted Mooney, P.E.  finishing.com Brick, NJ

1. Clean the steel surface; use abrasive paper, and if necessary degrease and dry.
2. Use "Decapoli 304/316" solution – shake well, then place one drop on the steel.
3. Place similar drops on standard 304 and 316 samples.
4. Darkening of the yellow drop in 2 to 4 minutes indicates significant Mo. Compare with indications on standard samples.
5. Wash or wipe samples clean.

DDD Tuck
- East St. Louis, IL, USA

The reader is looking for Damac 635 (or possibly 625) reagent to tell the difference between 304 and 316.

With regards,
P. Kemp

PETER KEMP
- SURREY ENGLAND

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