In the Pharmaceutical industry, stainless steel is used as per 21 CFR Part 211 Subpart – D Equipment, sec. 211.5, this guideline says that in pharmaceutical manufacturing, equipment product contact parts should be non-reactive, to achieve this stainless steel is used especially grade 316, 316L is mostly in use.

To detect the type of stainless-steel grade molybdenum spot test is used. for this, we require a reagent, 9v battery, and stainless-steel material to be tested. Molybdenum test kits are readily available in the market with ready-to-test instructions.

Procedure 

• Clean the surface of the test material where testing has to be done.

• Take the reagent bottle and place a drop of the reagent on the clean surface of the test metal.

• Then keep the negative side of the battery of 9v battery on the drop of reagent placed on the metal and the positive end of the battery on the plain surface.

• Then the drop turns red

• If the red color of the drop remains for 10 seconds, it is SS316.

• If the red color disappears immediately or turns green it is SS304

• If a stable black color develops & disappears in 2 seconds, it is SS302.

Note: Ammonium Metavanadate is the chemical compound present in the reagent diluted with water and it reacts with molybdenum to develop the color and the area on the metal where the test performed remains as a stain.