Local corrosion characteristics of CaS/CaO–MgO–Al2O3 inclusions in low-alloy steel under multi-factor mechanisms

Abstract

The influence of inclusions corrosion behavior under multi-factor local corrosion mechanisms was researched by SKPFM, TOF-SIMS, EBSD, and in-situ corrosion tests. The model of the local corrosion behavior of CaO/CaS–MgO–Al2O3 inclusion under the multifactor mechanism was established. The structural defect area at the boundary of the inclusions acted as the anodic phase where corrosion occurs preferentially, and the CaS of the inclusion underwent a chemical dissolution process. TiN, TiS2 and TiO2 were gradually shed, and the MgO, Al2O3 and CaO inside the local corrosion area were not completely shed. The gap defect of inclusion was the preferred condition to induce local corrosion when the matrix contains galvanic corrosion effect, dislocation region and the gap defect, and the process of anodic dissolution occurred in the dislocation region. There was no gap defect, the environment could not completely provide the driving force for local corrosion, and the possibility of non-local corrosion existed. The existence of gap defect provided the condition for the existence of solution, and provided the double layer contribution of potential difference of inclusion/matrix and solution.

Keywords

• Inclusion
• Local corrosion
• Dislocation region
• Volta potential
• Gap defect