为研究缝隙腐蚀的溶液化学和缝中金属阳极极化行为,设计一种楔形缝隙模拟装置.以碳钢为研究对象,分别测试了在3.5%(wt)NaCl溶液中缝内各位置的电极电位、Cl-浓度、pH值以及缝外阳极极化时电流密度的变化.结果表明:非极化状态下,距离缝口约2cm处的金属电位最负,最容易被腐蚀.缝外阳极极化促进缝隙腐蚀,并使得缝内溶液Cl-和H+富集更严重;缝口金属受极化影响,腐蚀加剧,而缝隙深处却由于沉积盐膜作用而受到保护
A self_made wedge_shaped simulated crevice apparatus was designed to investigate the solution chemistry in crevice of carbon steel and its anodic polarization behavior. For carbon steel with 3.5%(wt) NaCl , the change and the distribution of electrode potential , concentration of Cl- and pH value of solution in the crevice, and the current density of metal in the crevice were measured respectively under various conditions of anodic polarization. The results showed that without polarization the metal about 2 cm away from the opening of the crevice was attacked preferentially because of its lowest free corrosion potential. The anodic polarization promoted the corrosion in the crevice, and increased H+ and Cl- concentrated in the crevice. The metal at the mouth of crevice was corroded more seriously because of the polarization, but the metal at the deep of crevice was protected by the film of salt.
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