304 stainless steel is the stainless steel grade that we hear the most every day, but often we are prone to some misunderstandings because we don’t know about it. This issue will introduce 3 common misconceptions about 304 stainless steel.
Myth 1: 304 Stainless Steel Will Not Rust
The vast majority of people will think that stainless steel will never rust this idea is wrong. Stainless steel is never rust, just not easy to rust. Stainless steel surface has a layer of oxide film, that can isolate the oxygen atoms penetrating the oxidation, to obtain the ability to resist rust and corrosion. But once some reason to let this layer of protective film is damaged, this time the stainless steel will also rust.
Stainless Steel Rust
Why will 304 stainless steel rust?304 stainless steel has good corrosion resistance, but if specific conditions also occur in the cause of corrosion, the common reasons are:
First, chloride ions or the presence of other chemicals, resulting in the material being in a corrosive state thus accelerating the rust;
Second, without proper cleaning and maintenance, if the surface has dirt or other pollutants, it will damage the stainless steel surface passivation layer, putting the surface in a corrosion-prone state;
Third, the presence of iron oxide substances or rust, these substances will also damage the passivation layer on the surface of stainless steel, promoting the occurrence of rust.
Therefore, 304 stainless steel is a kind of steel that is not easy to rust, not a steel that never rusts. Therefore, it should be used in a reasonable application environment, and needs to be often scrubbed, in addition to dust, to keep it clean and dry; secondly, through the solid fusion treatment, so that the alloying elements into the body, increase the alloy content of the organization of the body, and improve the corrosion resistance; and finally is the surface treatment, brushed surface of 304 stainless steel is more prone to rust than the bright surface.
Myth 2: 304 Stainless Steel is Good Steel Without Magnetism
Many people think that stainless steel without magnetism is good stainless steel, proving that it is not easy to rust. This statement is very unscientific, stainless steel with or without magnetism is determined by its internal structure, stainless steel is in the process of smelting, due to the different temperatures of steel solidification, resulting in its internal structure being different.
Because there are many types of stainless steel, not all stainless steel is non-magnetic, such as martensitic stainless steel or ferritic stainless steel is magnetic, such as 430, 420, 410, and so on. No magnetic stainless steel refers to austenitic stainless steel, austenitic stainless steel is generally reflected in the non-magnetic or weakly magnetic, such as 304, 316.
304 stainless steel belongs to the austenitic structure of stainless steel, its magnetism is lower than a certain standard value, not that completely non-magnetic. But in the smelting process, easy to produce compositional segregation, or, in the process of cold processing, there will be a part of the austenitic structure to the ferrite structure to transform, that is, our common mechanical magnetism, which makes the 304 stainless steel will have a weak magnetic.
Myth 3: 304 Stainless Steel isFood Grade Stainless Steel
In the daily purchase of tableware, soup pots, and thermos cups, often see the logo printed on the top of the 304, do not be misled by the label, in fact, 304 stainless steel, is a common stainless steel, to meet market demand, it extends the 304L, 304N, 304H and so on.
First of all, 304 it is a U.S. brand, that appeared in China the manufacture itself is not right. 304 stainless steel Chinese brand, is 06Cr19Ni10, this represents, is the composition of its alloy.
Secondly, food-grade stainless steel to comply with national standards for lead, chromium, cadmium, nickel, and arsenic requirements, because heavy metals can not be degraded into the human body, they will interact with proteins and enzymes, so they are inactive, will also be precipitated in some organs of the human body, resulting in chronic poisoning.
So 304 stainless steel is not equal to food-grade stainless steel, to comply with GB4806.9-2016, which is the national definition of food-grade stainless steel.