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使用光学显微镜、电子探针、电子显微镜、微电化学测试等方法对两种低合金钢在海洋条件下的局部腐蚀锈层结构进行了研究。研究工作表明,低合金钢虽然具有较碳钢严重的局部腐蚀,但当该种合金钢的局部腐蚀锈层具有合金元素富集、致密等特征时,局部腐蚀将受到抑制,其原因是蚀坑内含富集合金元素的腐蚀产物成了难溶性盐,复盖了蚀坑底部基体,阻滞了腐蚀过程,降低了局部腐蚀速度。而在蚀坑外的平坦区域则没有发现合金元素的明显富集——局部腐蚀由向深度方向转而朝着扩大蚀孔直径的方向发展。这种变化的规律可由微电化学的蚀坑内外ΔmV-d曲线明显地看到所研究的钢种中,AlCuP钢具有较为典型的上述特征。NlCuAs钢的局部腐蚀行为与碳钢相近。
The corrosion structures of two kinds of low-alloyed steels in the ocean were studied by using optical microscope, electron probe, electron microscope and micro-electrochemical test. The research work shows that although the low alloyed steels have severe localized corrosion compared with that of the carbon steel, the local corrosion will be suppressed when the locally corroded rust layer of the alloyed steels has the characteristics of alloying elements enrichment and compactness, The corrosion products containing the enriched alloying elements become insoluble salts, covering the bottom of the pits, blocking the corrosion process and reducing the local corrosion rate. However, no obvious enrichment of the alloying elements was found in the flat areas outside the pits. The local corrosion developed from the direction toward the depth to the direction of expanding the diameter of the holes. The law of this change can be clearly seen by the ΔmV-d curve inside and outside the pits of the micro-electrochemical analysis. Among the studied steel grades, the AlCuP steel has the above typical characteristics. The local corrosion behavior of NlCuAs steel is similar to that of carbon steel.