Effects of deoxidizing degree on the pitting corrosion behavior of carbon and manganese steels

• Published in: International journal of minerals, metallurgy and materials metallurgy and materials, 2011-04, Vol.18 (2), p.169-177
• Main Authors: Cao, Guo-liang, Li, Guo-min, Chen, Shan, Chang, Wan-shun, Chen, Xue-qun
• Format: Article
• Language: English
• Subjects: Carbon; Ceramics; Characterization and Evaluation of Materials; Chemical analysis; Chemistry and Materials Science; Composites; Corrosion; Corrosion and Coatings; Corrosion cell; Corrosion effects; Corrosion tests; Deoxidizing; Electron probe microanalysis; Electron probes; Glass; Inclusions; Light microscopy; Manganese; Manganese steels; Materials Science; Metallic Materials; Microscopy; NaCl溶液; Natural Materials; Nucleation; Optical microscopy; Pitting (corrosion); Propagation; Saline solutions; Scanning electron microscopy; Seawater; Sodium chloride; Steel; Steels; Sulfides; Surfaces and Interfaces; Thin Films; Tribology; Water analysis; 扫描电子显微镜; 测试手段; 硫化物夹杂; 腐蚀行为; 闭塞腐蚀电池
• ISSN: 1674-4799; 1869-103X
• DOI: 10.1007/s12613-011-0418-9

Nine steels with different deoxidizing degrees and two comparative steels were selected. Their pitting initiation susceptibility was compared by means of potentiodynamic polarization tests in 3wt% NaCl solution. The pit propagation rate was evaluated in artificial sea water and 3wt% sea salt solution by simulating occluded corrosion cell （SOCC） test and hanging plate test, respectively. The composition of inclusions and corrosive feature were studied by scanning electron microscopy （SEM）, electron probe micro-analysis （EPMA）, and optical microscopy （OM）. The results indicate that sulfide inclusions in steel are the sites for pit nucleation. The sulphide inclusions vary in shape from short spindle-like to long strip-like with increasing deoxidizing degree. Under the same conditions, the lower the deoxidizing degree gets, the lower the pitting initiation susceptibility becomes, and the stronger the resistance to pit propagation exhibits. For steels with different deoxidizing degrees, their pitting initiation susceptibility is mainly influenced by thermodynamic stability, while the pit propagation rate is primarily subject to the characteristics of inclusions in steel.