Myth 1:
304 stainless steel will not rust
Most people think that stainless steel will never rust. In fact, this idea is wrong. Stainless steel doesn't never rust, it just doesn't rust easily. There is an oxide film on the surface of stainless steel, which can isolate oxygen atoms from penetrating into oxidation, thereby obtaining rust resistance. But once this protective film is damaged for some reason, stainless steel will also rust.
So why does 304 stainless steel rust? 304 stainless steel has good corrosion resistance, but it can also rust under certain conditions. Common reasons include:
First, the presence of chloride ions or other chemicals causes the material to be in a corrosive state and accelerates rust;
Second, without proper cleaning and maintenance, if there is dirt or other contaminants on the surface, it will damage the passivation layer on the surface of the stainless steel, making the surface susceptible to corrosion;
Third, the presence of iron oxide substances or rust will also damage the passivation layer on the surface of stainless steel and promote the occurrence of rust.
Therefore, 304 stainless steel is a kind of steel that is not easy to rust, not a steel that will never rust. Therefore, it must be used in a reasonable application environment, and needs to be scrubbed frequently, dust removed, and kept clean and dry; secondly, through solid solution treatment, the alloy elements are integrated into the body, increasing the alloy content of the body structure, and improving corrosion resistance; and finally, surface treatment , Brushed surface 304 stainless steel is more likely to rust than bright surface.
Misunderstanding 2: 304 stainless steel is good steel because it is non-magnetic
Many people think that stainless steel is good stainless steel if it is not magnetic, which proves that it does not rust easily. In fact, this statement is very unscientific. The non-magnetic nature of stainless steel strips is determined by its internal structure. During the smelting process of stainless steel, due to the different temperatures when the molten steel solidifies, its internal structures are different.
Because there are many types of stainless steel, not all stainless steel is non-magnetic. For example, martensitic stainless steel or ferritic stainless steel are magnetic, such as 430, 420, 410, etc. Non-magnetic stainless steel refers to austenitic stainless steel. Austenitic stainless steel generally exhibits non-magnetic or weak magnetism, such as 304 and 316.
304 stainless steel is a stainless steel with an Austrian structure. Its magnetism is lower than a certain standard value, which does not mean that it is completely non-magnetic. However, during the smelting process, component segregation is likely to occur, or during cold working, a part of the austenite structure will transform into a ferrite structure, which is our common mechanical magnetism. This also makes 304 stainless steel Will have weak magnetism.
Myth 3: 304 stainless steel is food grade stainless steel
When we buy tableware, soup pots and thermos cups on a daily basis, we often see the 304 logo printed on them. Don’t be misled by this label anymore. In fact, 304 stainless steel is just an ordinary stainless steel. In order to adapt to market demand, it has been extended to 304L, 304N, 304H, etc.
First of all, 304 is an American brand, and it is wrong to appear on something made in China. The Chinese brand name of 304 stainless steel is 06Cr19Ni10, which represents the composition of its alloy.
Secondly, food-grade stainless steel must meet the national standards for lead, chromium, cadmium, nickel, and arsenic. Because heavy metals cannot be degraded and enter the human body, they will interact with proteins and enzymes, causing them to lose their activity. It will precipitate in certain organs of the human body, causing chronic poisoning.
Therefore, 304 stainless steel is not equal to food-grade stainless steel. It must comply with GB4806.9-2016. This is the definition of national food-grade stainless steel.
