Common Problems and Measures for the Acid Pickling and Passivation Treatment of Stainless Steel
Stainless steel is widely used in our daily life due to its excellent corrosion resistance and environmental adaptability. However, due to long-term use or use in some corrosive medium environments, its surface will be corroded and oxidized, resulting in stainless steel losing its excellent characteristics. In order to restore or improve the corrosion resistance of stainless steel surface, the known and commonly used methods are surface mechanical polishing and chemical conversion treatment such pickling and passivation.
The acid pickling and passivation process of stainless steel is a chemical and electrochemical reaction, which can remove the rust or the oxide scale or dirt on the surface of steel and realize the passive passivation (or passivation) of steel surface. This process is widely used in food industry, pharmaceutical industry, medical research and other industries, which have a huge impact on our lives and production. But because there are many factors involved in the pickling and passivation of stainless steel such as material, composition, environment and operation technique, sometimes it is inevitable that some undesirable problems will occur. Therefore, it is necessary to understand the common problems in the acid pickling and passivation of stainless steel and the corresponding preventive measures.
A common problem in the process of acid pickling and passivation of stainless steel is the uneven pickling. Some areas are over-pickled, the surface of stainless steel is white, or even pits appear, while other areas are dark and some decontamination is not thorough. This situation is caused by uneven pickling agent, improper temperature control, improper operation and uneven steel surface, etc. Therefore, if encounter this situation during the acid pickling and passivation of stainless steel, should take measures to clean the area that is over-pickled, to strictly control the temperature, operation and stainless steel surface uniformity in subsequent processing or to choose stainless steel that is not easily contaminated.
Another problem is the black spots on the surface of stainless steel. These spots are caused by excessive impurities and residual traces in the pickling liquid, incomplete cleaning of the pickling liquid on the surface of stainless steel, and also by not drying after washing. In order to prevent this problem from happening, it is necessary to choose qualified pickling liquid, regularly clean the pickling liquid, and use sandpaper to remove the residual pickling liquid on the surface of the steel before washing and drying.
In addition, the whitening caused by excessive pickling broth is another common problem. This problem will arise due to excessive concentration of the pickling liquid, prolonged time of soaking and scouring, and too high temperature. In order to avoid this problem, it is necessary to choose a qualified pickling liquid, strictly control the concentration, soaking and scouring time as well as the temperature.
Above are the common problems and solutions in the acid pickling and passivation of stainless steel. In practical operation, these problems often occur, and sometimes need to be solved one by one. Therefore, in order to ensure the quality of acid pickling and passivation of stainless steel, it is necessary to strictly control the factors that may cause these problems. Finally, always remember that the acid pickling and passivation of stainless steel requires professionals. Therefore, it is recommended to find a professional company for processing to ensure the best quality.
