The use of most steel pipes is required to maintain the original appearance of the building for a long time. In determining the type of stainless steel to be selected, the main consideration is the required aesthetic standards, the corrosion of the location of the atmosphere and the cleaning system to be used. However, other applications increasingly seek only structural integrity or impermeability. For example, the roofs and side walls of industrial buildings. In these applications, the owner's cost of construction may be more important than aesthetics, even if the surface is not very clean. 304 stainless steel works quite well in dry indoor environments. However, in rural and urban areas, it is necessary to wash frequently if it wants to maintain its appearance outdoors. In heavily polluted industrial areas and coastal areas, the surface can be very dirty and even rust. But to achieve the aesthetic effect in the outdoor environment, it is necessary to use nickel-containing stainless steel. Therefore, 304 stainless steel is widely used in curtain wall, side wall, roof and other architectural purposes, but in the serious erosion of the industrial or Marine atmosphere, the best use of 316 stainless steel. Now, people have fully realized the advantages of using stainless steel in structural applications. 304 and 316 stainless steel are included in several design guidelines. Because "duplex" stainless steel 2205 has combined good atmospheric corrosion resistance with high tensile strength and elastic limit strength, this steel is also included in the European guidelines. In fact, stainless steel is manufactured in all standard metal shapes and sizes, and there are many special shapes. The most commonly used products are made of sheet and strip steel, as well as medium and thick plates for special products, for example, hot rolled structural sections and extruded structural sections. There are also round, oval, square, rectangular and hexagonal welded pipe or seamless steel pipe and other forms of products, including profiles, bars, wires and castings.
In fact, stainless steel is manufactured in all standard metal shapes and sizes, and there are many special shapes. The most commonly used products are made of sheet and strip steel, as well as medium and thick plates for special products, for example, hot rolled structural sections and extruded structural sections. There are also round, oval, square, rectangular and hexagonal welded pipe or seamless steel pipe and other forms of products, including profiles, bars, wires and castings. When the chromium content reaches 10.5%, the atmospheric corrosion resistance of the steel is increased significantly, but when the chromium content is higher, the corrosion resistance is still improved, but not obvious. The reason is that when the steel is alloyed with chromium, it changes the type of surface oxide that is similar to that formed on pure chromium metals. This tightly adhered chromium-rich oxide protects the surface from further oxidation. This oxide layer is extremely thin, through which the natural luster of the steel surface can be seen, giving stainless steel its unique surface. Moreover, if the surface is damaged, the exposed steel reacts with the atmosphere to repair itself, re-forming this "passivation film" that continues to protect. Therefore, all stainless steel has a common characteristic, that is, chromium content is more than 10.5%.
