There are many kinds of stainless steel, which can be divided into austenite, martensite and ferrite at normal temperature. Austenite is nonmagnetic or weakly magnetic, and martensite or ferrite is magnetic. However, it is not necessarily so. As is commonly used as a decoration tube plate Austenitic 304 material, generally there is no magnetic, but fluctuations in chemical composition caused by smelting or processing of different magnetic properties may also appear, it can not be considered to be counterfeit or substandard. In addition, 304 stainless steel after cold processing, the organizational structure will also be converted to martensite, cold processing deformation degree, the more martensitic transformation, the greater the magnetic properties of steel. On the contrary, the 200 series stainless steel, which is inferior in quality, is likely to be non-magnetic. Therefore, it is a great mistake to judge that it is genuine stainless steel.

People often depend on the magnet to absorb stainless steel to determine its good or bad. In fact, this is an impractical way of distinguishing. Relying on traditional methods of distinguishing stainless steel with magnetism is likely to suffer. Stainless steel refers to: in the atmosphere and acid, alkali, salt and other corrosive medium, showing dull, corrosion-resistant and not rust high chromium (generally 12%~30%) alloy steel. The corrosion resistance of stainless steel depends on the alloying elements contained in the steel. The basic alloying elements of stainless steel, as well as nickel, molybdenum, titanium, niobium, copper, nitrogen and so on, to meet the various requirements for the use of stainless steel structure and performance. Stainless steel is easy to chloride corrosion, because chromium nickel chloride is collocated elements, elements will be collocated to form stainless steel corrosion exchange assimilation.

In determining the type of stainless steel to be chosen, the main consideration is the aesthetic standards required, the corrosivity of the atmosphere in the area, and the cleaning system to be adopted. However, other applications increasingly seek only structural integrity or watertightness. For example, the roof and side walls of industrial buildings. In these applications, the construction cost of the owner may be more important than the aesthetic, the surface is not very clean can also. The use of 304 stainless steel in a dry indoor environment is quite effective. But in rural and urban areas, it is often necessary to wash them in order to keep them in the open. In the heavily polluted industrial and coastal areas, the surface can be very dirty and even rust. But to obtain the aesthetic effect of outdoor environment, it is necessary to use nickel stainless steel.