How to Select Stainless Steel and Its Corrosion Resistance

Most steel pipes require long-term maintenance of the original appearance of the building. In determining the type of stainless steel to be selected, the main consideration is the required aesthetic standards, the corrosiveness of the atmosphere and the cleaning system to be adopted. However, other applications are increasingly seeking structural integrity or impermeability. For example, roofs and sidewalls of industrial buildings. In these applications, the construction cost of the owner may be more important than aesthetics, and the surface is not very clean. The effect of 304 stainless steel in dry indoor environment is quite good. However, in rural and urban areas, if you want to maintain its appearance outdoors, you need to wash regularly. In heavily polluted industrial areas and coastal areas, the surface will be very dirty, and even rust. But in order to obtain the aesthetic effect in outdoor environment, it is necessary to use stainless steel containing nickel. Therefore, 304 stainless steel is widely used for curtain wall, side wall, roof and other architectural purposes, but 316 stainless steel is preferred in the corrosive industrial or marine atmosphere. Now, people have fully realized the advantages of using stainless steel in structural applications. Several design criteria include 304 and 316 stainless steel. Because duplex stainless steel 2205 combines good atmospheric corrosion resistance with high tensile strength and elastic limit strength, it is also included in the European Standards. In fact, stainless steel is manufactured in full standard metal shape and size, and there are many special shapes. The most commonly used products are sheet and strip steel. Special products are also produced from medium and heavy plates, such as hot-rolled structural steel and extruded structural steel. There are also round, oval, square, rectangular and hexagonal welded pipes or seamless steel pipes and other products, including profiles, bars, wires and castings.
In fact, stainless steel is manufactured in full standard metal shape and size, and there are many special shapes. The most commonly used products are sheet and strip steel. Special products are also produced from medium and heavy plates, such as hot-rolled structural steel and extruded structural steel. There are also round, oval, square, rectangular and hexagonal welded pipes or seamless steel pipes and other products, including profiles, bars, wires and castings. When the content of chromium reaches 10.5%, the atmospheric corrosion resistance of steel increases remarkably, but when the content of chromium is higher, the corrosion resistance is still improved, but it is not obvious. The reason is that when chromium is used to alloying steel, the type of surface oxide is changed to a surface oxide similar to that formed on pure chromium metal. This tightly adhered chromium-rich oxide protects the surface from further oxidation. This kind of oxide layer is very thin, through which the natural luster of steel surface can be seen, so that stainless steel has a unique surface. Moreover, if the surface is damaged, the exposed steel surface will repair itself with the atmospheric reaction, forming the "passive film" again, and continue to play a protective role. Therefore, all stainless steels have a common characteristic, that is, the chromium content is above 10.5%.