The content of chromium in 304 stainless steel is 18-19%, and the content of NI is 8.0-8.9%. Due to its high nickel content, it has been greatly enhanced in terms of corrosion resistance. It can be used for more than 15 years in a general environment. In harsh environments (such as coastal areas, areas with serious industrial pollution), it can be maintained for about 5 years. Many users think that the rust of stainless steel is the quality problem. In fact, this is a one-sided understanding. Stainless steel is only more resistant to corrosion. Stainless steel manufacturers recommend that customers choose 304 stainless steel when used outdoors, because the corrosion resistance of 304 stainless steel is several times stronger than that of 201 stainless steel under the same environment. When we choose stainless steel, we can’t distinguish between 201 and 304 stainless steel with the naked eye. When we buy it, we ask the supplier for the inspection report of the stainless steel composition, or use the stainless steel testing potion to identify its material.