Source: Big Head Chat
Let's start with the conclusion: 304 and 316 stainless steel can be safely used in contact with food, but 316 stainless steel is more corrosion-resistant and has a longer life than 304 stainless steel.
316 stainless steel
316 stainless steel is often used in medical devices, and contains a higher content of molybdenum metal, which makes its chemical properties more stable than 304 stainless steel, especially the corrosion resistance to chlorides such as edible salt. The 316L is a low-carbon version, which is not much different from 316 stainless steel in use. The general children's thermos cup is made of 316 stainless steel, which is of high standard.
304 stainless steel
Our common thermos cups and stainless steel lunch boxes are basically 304 material, its cost is relatively low, usually, 304 stainless steel products or its ancillary documents will be marked with "304", stainless steel tableware without any digital markings do not meet the national standards, use with caution.
How to distinguish between 304 stainless steel and 316 stainless steel?
304 stainless steel contains a certain amount of magnetism because it contains more chromium elements. Whereas, 316 stainless steel contains less chromium and is almost non-magnetic. Therefore, magnetic testing can be used to preliminarily distinguish between them.
The most intuitive way to distinguish this is to mark the numbers on the cutlery or thermos cup. So some people will ask, will there be 304 stainless steel marked as 316 stainless steel? The answer is basically impossible. For the act of arbitrarily marking the product model or false label, the mainland law also stipulates the corresponding punishment measures, and will face huge fines and revocation of business licenses, so arbitrary labeling is an illegal act and a red line that cannot be crossed.
How do I check if I meet the specifications?
The most convenient detection method for civil use is to use 304 stainless steel detection liquid and 316 stainless steel detection liquid, and drop it into the container to see if it is discolored.
Turning red is 201 stainless steel, which will release a large amount of harmful metals during use, and cannot be used for food. The price of the test solution is very cheap, and you can buy it for a few dollars. It is recommended that you can always have the first one at home, and you can measure it when you buy a metal container.