Susceptibility of high strength low alloy steel to localized corrosion was studied in 6.7 M CaCl_2 for oil and natural gas drilling applications. Results of the immersion and electrochemical experiments showed that the steel is susceptible to pitting corrosion. Optical microscopy investigations of the polished samples revealed that 10% of the surface area was occupied by defects in the form of pits. The energy dispersive X-ray (EDX) and wavelength dispersive X-ray (WDX) chemical analyses revealed higher concentrations of Mn and S compared to the metal matrix in defected areas. These areas served as the sites for development of corrosion pits during both immersion and electrochemical experiments. The fatigue results of the corroded samples indicate that if the pit was the most significant defect, the fatigue crack initiated and propagated at this site.
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机译：在石油和天然气钻井应用中，在6.7 M CaCl_2中研究了高强度低合金钢对局部腐蚀的敏感性。浸没和电化学实验的结果表明，钢很容易发生点蚀。对抛光样品的光学显微镜研究表明，表面积的10％被凹坑形式的缺陷所占据。能量色散X射线（EDX）和波长色散X射线（WDX）化学分析显示，与缺陷区域中的金属基质相比，锰和硫的浓度更高。在浸没和电化学实验中，这些区域都是腐蚀坑的形成场所。腐蚀样品的疲劳结果表明，如果凹坑是最明显的缺陷，则疲劳裂纹会在该部位开始并扩展。
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