With two samples of steel 304 and 316 can not be distinguished by the naked eye, but must cut the sample and use a chemical analyzer. However, there is a simpler method to quickly distinguish the two types of steel grades.
Usually to distinguish these two types of stainless steel is a relatively simple and less expensive method that uses reagents to create an electrochemical corrosion reaction on the surface. The difference of these two types is that the element Mo content is only available in 316 steel grade. The reagent is sprayed directly on the surface 304 and 316, after the electrochemical corrosion reactions occur, check the discolouration of Products with naked eyes can identify the two products above.
The reagents used have ingredients: SnCl2-30g, NH4SCN-10g and 100cc distilled water, this reagent is very corrosive, so it must be stored in a glass jar and carefully labeled. Conditions to create surface reactions, it is necessary to use wire with a cross section greater than 3mm and a 9V battery to handle.
Specific ways to do the following:
- Wash the surface to remove impurities.
- Soak the sample in reagent solution in accordance with the ratio of SnCl2-30g, NH4SCN-10g and 100cc distilled water.
- The power cord is connected to the positive terminal of the battery and is not connected to the solution storage area, this area is used to connect the negative end of the battery.
- Observe the color change on the reagent container, if the surface turns red, it is 316 steel grade.
- Note that when the testing process is complete, it is necessary to clean the solution on the surface to avoid corrosion.
However, this test method depends much on the factors of temperature, reagent quality, level of performers ... Therefore, if you want accurate results, it still needs analyzers to meet quality standards.
Source: tygico.com