Stainless steel is an important and widely used steel grade, known for its corrosion resistance and rust resistance. Generally, stainless steel is recommended in food manufacturing because it can eliminate the problem of rust. It is also called Inox steel in metallurgy, which means non-oxidizable steel.
This ideal performance of stainless steel is due to the high content of chromium present in the steel. This makes it very different from other carbon steel alloys. Other types of steel undergo an oxidation process when exposed to heavy oxygen and moisture, forming iron oxide. Compared with steel, iron oxide has a much lower density and is softer, so it easily breaks into flakes, which further rusts the underlying coating.
Mo Ju would like to remind you that stainless steel will also oxidize, but the difference lies in the type of oxide formed. In the presence of oxygen and water, stainless steel forms a layer of chromium oxide on its surface. This compound is inert and prevents more forms of oxygen from contacting the rest of the steel, thereby protecting the material from further damage. The process of forming an inert layer of chromium oxide is called passivation and depends on the high concentration of chromium in the alloy. But what Mo Ju wants to remind you is that in low oxygen or high salinity environments, stainless steel may be corroded.
Stainless steel composition: Stainless steel contains at least 10.5% chromium, but this value depends on the required properties. 13% of chromium is sufficient to prevent oxidation at room temperature, and in extreme environments, the proportion can rise to 26%. Chromium forms chromium(III) oxide, which is an invisible compound that maintains gloss and a smooth surface. Another advantage of this layer is that if the surface is scratched, it can quickly re-form. Certain other metals (such as titanium and aluminum) also have this passivation characteristic.
Acid resistance: In addition to oxygen and moisture, stainless steel can also resist various concentrations of acid. It also depends on the temperature and the type of steel and acid. Most types of stainless steel can resist the attack of phosphoric acid, and some stainless steels (such as SS 904) can resist the attack of sulfuric acid at room temperature and high concentration. However, Mo Ju would like to remind you that certain types of SS 304 will corrode in the presence of sulfuric acid. Hydrochloric acid is an acid that will corrode all types of stainless steel and should be avoided.
Application of stainless steel: The characteristics of stainless steel make it very popular in many applications. It has the strength of steel, rust resistance and a bright and attractive appearance. It can be cleaned easily with water or steam and does not require painting. Stainless steel is produced in the form of coils, sheets, plates, bars and wires. Stainless steel SUS304 is used to make tableware, cooking utensils, surgical equipment and some electrical appliances. Stainless steel is also widely used in manufacturing industrial equipment, such as storage tanks for liquids. These materials benefit from their corrosion resistance and can be used in automobiles, aerospace applications, and construction.