Stainless steel should be familiar to all of us. In our lives, too many things are made of stainless steel. When shopping for household stainless steel products, we can often see a series of numbers before the word “stainless steel”. The most common numbers are 304 and 316. What do these numbers mean? Which one should we choose?
Stainless steel is not only not rusty
We all know that the main component of steel is iron. The chemical properties of iron are relatively active, and it is easy to chemically react with the surrounding things. The most common reaction is oxidation, where iron reacts with oxygen in the air, which is commonly known as rust.
Add some impurities (mainly chromium) to the steel to form stainless steel. But the ability of stainless steel is not only anti-rust, this can be seen from its full name: stainless and acid-resistant steel. Stainless steel is not only resistant to oxidation, but also resistant to acid corrosion.
All stainless steels are resistant to oxidation, but the types and proportions of impurities inside are different, and the ability to resist acid corrosion is also different (sometimes we see that the surface of some stainless steels is still rusty because it is corroded by acid). In order to distinguish the acid corrosion resistance of these stainless steels, people have specified different grades of stainless steel.
304 stainless steel and 316 stainless steel
304 and 316 are the more common stainless steel grades in our lives. We can simply understand it as: the larger the number, the stronger the acid corrosion resistance of stainless steel.
There are stainless steels that are less resistant to acid corrosion than 304 stainless steel, but those stainless steels cannot meet food contact requirements. Common daily foods may corrode stainless steel. It is not good for stainless steel, and it is even worse for the human body. For example, stainless steel railings use 201 stainless steel.
There are also stainless steels that are more resistant to acid corrosion than 316 stainless steel, but the cost of those stainless steels is too high. Things that can corrode them are hard to see in life, so we don’t need to invest too much in this aspect.
Food grade stainless steel
First of all, in the standard, it is not specified which grade of stainless steel is food grade stainless steel. In the “National Food Safety Standard Stainless Steel Products (GB 9684-2011)”, a series of corrosion resistance requirements for food contact stainless steel are specified.
Later, after comparing these requirements, people found that the minimum standard of stainless steel that can meet these requirements is 304 stainless steel. So there is the saying that “304 stainless steel is food grade stainless steel”. However, everyone should be able to understand here that this statement is not accurate. If 304 can be in contact with food, then 316 stainless steel, which is more resistant to acid and corrosion than 304 stainless steel, can naturally be-better than 316 stainless steel. They can naturally be used for food contact.
So there is the ultimate question: Should I choose the cheaper 304 for household use or the higher price 316?
For stainless steel in general locations, such as faucets, sinks, racks, etc., 304 stainless steel is sufficient. For some stainless steels that are in close contact with food, especially with a variety of foods, such as tableware, water cups, etc., you can choose 316 stainless steel-304 stainless steel contact with dairy products, carbonated drinks, etc., will still be corroded.
Post time: Apr-19-2021