What are the taboos to buy used stainless steel products?
Issuing time:2018-09-26 00:00
As kitchen supplies, stainless steel products are easy to clean, inexpensive, and not easy to rust, easy to store, are very common utensils and tools in our life.
But in recent years, with the increasing demand for stainless steel tableware, some inferior products also appear in the market.
What harm does inferior stainless steel tableware have to the body? How to identify and select high quality stainless steel products?
Why can stainless steel be used as tableware?
Stainless steel, also known as stainless acid resistant steel. As the name suggests, it will not rust like ordinary steel, but also can withstand the corrosion of acid, alkali, salt and other chemical media.
Stainless steel is mainly composed of iron, chromium, nickel, a small amount of carbon and other trace elements.
Stainless steel "rust" and "corrosion" secret is that it contains a certain amount of chromium. Together with other elements, chromium forms a dense oxide film on the surface of stainless steel to prevent the internal material from contacting with air. This film is very thin, through which you can see the luster of the steel surface, so stainless steel always looks bright.
Interestingly, even if the surface of stainless steel is damaged, the exposed part will react with oxygen in the air to self repair and re form a "chromium rich passive film". This is the secret that stainless steel tableware is not easy to rust and resistant to acid and alkali.
According to the material structure, stainless steel can be divided into three categories: austenitic stainless steel, ferritic stainless steel and martensitic stainless steel. Because of the different content of chromium and nickel, the corrosion resistance and application category of the three kinds of stainless steels are also different.
We are familiar with 304 stainless steel belongs to austenitic stainless steel, also known as 18-8 steel, which means 18% chromium and 8% nickel, and is mostly used for ordinary kitchen utensils; the common austenitic stainless steel is 316 stainless steel, which has higher nickel content than 304, less carbon content, higher corrosion resistance, and added molybdenum element. Of course, the cost is higher. It is mainly used in food industry and surgical equipment And so on.
Therefore, although stainless steel is good, it can not be used to make tableware and cookware.
China has strict regulations on food grade stainless steel in direct contact with food, only in line with the national mandatory standard gb4806.9-2016 "national food safety standard" The standard limits the upper limit of migration amount of arsenic, cadmium, lead, chromium and nickel in stainless steel products under specific measurement methods.