How to identify stainless steel type used on your stainless steel vacuum flask? Today we would like to introduce a simple method.

As you may know that, in the industry of s/s vacuum flask industry, the most conventional stainless steel type are 201 stainless steel and 304 stainless steel.

304 stainless steel is a kind of food grade material, which can pass FDA, LFGB test. They are usually used as the inner liner of stainless steel vacuum flask and won’t get rust. While 201 stainless steel is easy to rust. So 304 stainless steel are more food safe as liner of vacuum flask.

How to identify 304, 201 and other stainless steel type? We would to recommend a special chemical reagent for stainless steel material testing. —-Mn content testing reagent.

Mn content testing reagent

Mn content testing reagent

As we know, all 200 series of stainless steel content Mn element. For examples, 201 stainless steel content 6% Mn, while 304 stainless steel content nearly zero Mn. By this reagent, we can identify whether stainless steel material content Mn or not, then we can know whether it’s 304 or 201 s/s.

You just need to put one drop of identification solution on the surface of stainless steel, then see whether the solution change into red color or not.

  1. 200 stainless steel: It turns red in 2 seconds, brown in 10 seconds, and manganese exceeds the standard.
  2. 201 & 202 stainless steel: It turns red in about 35-40 seconds, manganese exceeds the standard.
  3. 301 stainless steel: It turns pale red in about 50 seconds.
  4. 304 & 316 stainless steel: It won’t turn red in 1 minute.

stainless steel type testing

Please see above chromatographic strip of the standard chart below to confirm the type of stainless steel. The faster the change, the lower quality the material is!

As a professional supplier of stainless steel vacuum flask, Hono Housewares use all 304 stainless steel for the components which contact drinks. It’s our basic quality requirement to make sure our vacuum flask food safe for consumers. For more information about our products and material, please see our FAQ.