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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 structures of the rust layers of two low alloy steels formed by localized corrosion in marine environment were investigated. Optical microscope, electron probe, EM and microelectrochemical testing show that although the low alloy steel corrodes faster than ordinary carbon steel, but when the rust layers formed are dense and enriched with alloying elements, the corrosion processes will be inhibited. These corrosion products can form sparingly soluble salts and cover the bottom of the pits, while outside the pits this phenomena will not occur and the corrosion processes turn to enlarge the radius of the pits, as can be confirmed by the difference of the microelectrochemical mv-d curves inside and outside the pits. From the types of steels investigated, Al-Cu-P steel has more typical above mentioned characteristic, and the localized corrosion behavior of the Ni-Cu-As steel is nearly the same as that of the carbon steel.