Role of surface finish and post-fabrication cleaning on localised corrosion of type 316L austenitic stainless steel flash chambers

British Corrosion Journal Pub Date : 2001-03-01 DOI:10.1179/bcj.2001.36.3.184

F. El Shawesh, A. El Houd, O. Raghai

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引用次数: 6

Abstract

Abstract Several carbon steel flash chambers clad with type 316L austenitic stainless steel and operating in seawater at 80°C exhibited severe localised corrosion on the inner wall after three months of continuous service. Visual investigation, carried out on the corroded wall surfaces revealed that the corrosion attack was confined to mechanically damaged and iron-contaminated areas. Failure to keep the oxygen level within the allowable limit of 0·026 ppm had promoted the corrosion. Electrochemical studies confirmed the influence of surface condition apparent from the visual inspections. Various specimens of type 316L austenitic stainless steel with different surface finishes (as received, ground, mechanically scratched, and iron contaminated) were exposed to natural sea water at 80°C Metallographic examination revealed that pits which formed on the as received specimens were uniform in shape, while those on specimens with mechanically damaged surfaces were larger and irregular in shape. The results suggest that surface finish exerted a significant influence on the rapid corrosion of the flash chambers. Post-fabrication cleaning by acid pickling markedly improved the resistance of the type 316L specimens to localised corrosion (pitting). However, the results of acid pickling were dependent on the surface condition and, to a large extent, the temperature of the acid.

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316L型奥氏体不锈钢闪蒸室的表面处理和加工后清洗对局部腐蚀的影响

在80℃海水环境中连续使用3个月后，几个碳钢闪蒸室内壁出现了严重的局部腐蚀。对腐蚀壁面进行的目视调查显示，腐蚀仅限于机械损坏和铁污染的区域。未能将氧含量保持在0.026 ppm的允许范围内，促进了腐蚀。电化学研究证实了表面状况的影响是显而易见的。将316L型奥氏体不锈钢不同表面处理(接收、研磨、机械划伤、铁污染)的试样置于80℃的自然海水中，金相检查发现，接收试样表面形成的凹坑形状均匀，而机械损伤试样表面形成的凹坑较大且形状不规则。结果表明，表面光洁度对闪蒸室的快速腐蚀有显著影响。制造后的酸洗清洗明显提高了316L型试样对局部腐蚀(点蚀)的抵抗能力。然而，酸洗的结果取决于表面状况，在很大程度上取决于酸的温度。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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British Corrosion Journal

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