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为了探究低合金钢中夹杂物在低pH值,高浓度氯离子腐蚀环境下诱发点蚀的作用机理,利用pH为0.85的10%NaCl溶液,模拟货油舱下底板腐蚀环境,采用扫描电镜(SEM)、X射线能量色散谱(EDS)、夹杂物原位观察等手段,分析了不同类型、尺寸、形状的夹杂物对E36级船板钢点蚀行为的影响。结果表明:试验钢中存在MnS、TiO2等不同类型的夹杂,夹杂物在酸性溶液中最先被溶解,是点蚀的诱发源。夹杂物周围存在直径10μm左右的阴极保护区,在早期不易被腐蚀。此外,不同类型和形状的夹杂物诱发点蚀的优先顺序不同,MnS较TiO2优先诱发点蚀,长宽比大的夹杂较圆形夹杂优先诱发点蚀。
In order to investigate the mechanism of pitting induced by inclusions in low alloyed steel under low pH and high concentration of chloride ions, the corrosive environment of the bottom plate of cargo tank was simulated by using 10% NaCl solution with pH value of 0.85. Scanning electron microscopy SEM, X - ray energy dispersive spectroscopy (EDS) and in situ observation of inclusions. The effects of different types, sizes and shapes of inclusions on the pitting corrosion behavior of E36 ship steel were analyzed. The results show that there are different types of inclusions such as MnS and TiO2 in the test steel, and the inclusions are the first to be dissolved in acid solution, which is the inducing source of pitting corrosion. Inclusion around the existence of a diameter of about 10μm cathodic protection zone, not easily corroded in the early. In addition, different types and shapes of inclusions have different priority in inducing pitting corrosion. MnS preferentially induces pitting corrosion compared with TiO2, and inclusions with larger aspect ratio than circular inclusions preferentially induce pitting corrosion.