Scientists Refreshing the Understanding Scale of Stainless Steel Pitting Mechanism
Recently, a team led by Ma Xiuliang, a researcher at the Shenyang National (Joint) Laboratory of Materials Science, Institute of Metals, Chinese Academy of Sciences, found that oxide (MnCr2O4) nanoparticles with octahedral structure were dispersed in manganese sulfide inclusions using high-resolution transmission electron microscopy. In situ environmental (external) electron microscopy studies under simulated material activation conditions indicate that the presence of these nano oxides is equivalent to the intrinsic small "tumors" in manganese sulfide. Under certain medium conditions, the local dissolution of manganese sulfide originates at the interface between it and the "tumor" and gradually expands into the material body.
Research has also shown that there is a difference in the local dissolution rate of manganese sulfide caused by oxide nano octahedra. On this basis, the research team collaborated with Professor Hu Peijun from Queen's University of Belfast in the UK to determine that oxide nanooctahedra with strong activity and easy dissolution of manganese sulfide around them have the characteristic of metal ions as their outer surface (similar to "malignant tumors"); On the contrary, lower activity nano octahedra use oxygen ions as their outer surface (similar to "benign tumors"). This discovery provides direct evidence for revealing the initial location of manganese sulfide dissolution in the initial stage of stainless steel pitting corrosion, elevating people's understanding of the mechanism of stainless steel pitting corrosion from the previous micrometer scale to the atomic scale, and providing atomic scale structural and compositional information for exploring new ways to improve the resistance of stainless steel to pitting corrosion. This research result was recently published online in Acta Materialia (Journal of Materials).
The surface of stainless steel has high corrosion resistance due to the formation of a dense chromium oxide film, making it widely used in modern industrial fields and daily life. However, while resisting uniform corrosion, local pitting corrosion (i.e. pitting corrosion) of stainless steel is difficult to avoid. The occurrence of pitting corrosion starts at the material surface and undergoes two stages of nucleation and growth, ultimately rapidly expanding in the depth below the material surface. Therefore, pitting damage has great concealment and suddenness. Especially in fields such as petroleum, chemical, and nuclear power, pitting corrosion can easily cause pipe wall perforation, leading to a large amount of oil and gas leakage, and even causing disasters such as fires and explosions.
Since the 1930s, human exploration of the nucleation mechanism of stainless steel pitting has never been interrupted, and pitting has become one of the classic problems in the field of materials science and engineering. Although researchers generally believe that the occurrence of pitting corrosion is due to the local dissolution of manganese sulfide inclusions in stainless steel, the initial nucleation position of pitting corrosion is described as "random and unpredictable" due to the lack of microscale structural and compositional information. The ambiguity of the initial position of pitting has always constrained people's understanding of the pitting mechanism of stainless steel and the improvement of anti pitting measures.
The mechanical properties of steel materials have long been widely concerned about the damage caused by micrometer scale oxide inclusions, and have been effectively controlled. For example, in metallurgical technology, "ultra clean" steel is obtained by reducing the size of non-metallic inclusions. Ma Xiuliang et al.'s research shows that even if the size of oxides is reduced to the nanoscale, they can still damage the material structure through electrochemical pathways. Therefore, a small ruler
Research has also shown that there is a difference in the local dissolution rate of manganese sulfide caused by oxide nano octahedra. On this basis, the research team collaborated with Professor Hu Peijun from Queen's University of Belfast in the UK to determine that oxide nanooctahedra with strong activity and easy dissolution of manganese sulfide around them have the characteristic of metal ions as their outer surface (similar to "malignant tumors"); On the contrary, lower activity nano octahedra use oxygen ions as their outer surface (similar to "benign tumors"). This discovery provides direct evidence for revealing the initial location of manganese sulfide dissolution in the initial stage of stainless steel pitting corrosion, elevating people's understanding of the mechanism of stainless steel pitting corrosion from the previous micrometer scale to the atomic scale, and providing atomic scale structural and compositional information for exploring new ways to improve the resistance of stainless steel to pitting corrosion. This research result was recently published online in Acta Materialia (Journal of Materials).
The surface of stainless steel has high corrosion resistance due to the formation of a dense chromium oxide film, making it widely used in modern industrial fields and daily life. However, while resisting uniform corrosion, local pitting corrosion (i.e. pitting corrosion) of stainless steel is difficult to avoid. The occurrence of pitting corrosion starts at the material surface and undergoes two stages of nucleation and growth, ultimately rapidly expanding in the depth below the material surface. Therefore, pitting damage has great concealment and suddenness. Especially in fields such as petroleum, chemical, and nuclear power, pitting corrosion can easily cause pipe wall perforation, leading to a large amount of oil and gas leakage, and even causing disasters such as fires and explosions.
Since the 1930s, human exploration of the nucleation mechanism of stainless steel pitting has never been interrupted, and pitting has become one of the classic problems in the field of materials science and engineering. Although researchers generally believe that the occurrence of pitting corrosion is due to the local dissolution of manganese sulfide inclusions in stainless steel, the initial nucleation position of pitting corrosion is described as "random and unpredictable" due to the lack of microscale structural and compositional information. The ambiguity of the initial position of pitting has always constrained people's understanding of the pitting mechanism of stainless steel and the improvement of anti pitting measures.
The mechanical properties of steel materials have long been widely concerned about the damage caused by micrometer scale oxide inclusions, and have been effectively controlled. For example, in metallurgical technology, "ultra clean" steel is obtained by reducing the size of non-metallic inclusions. Ma Xiuliang et al.'s research shows that even if the size of oxides is reduced to the nanoscale, they can still damage the material structure through electrochemical pathways. Therefore, a small ruler
