具有剥离涂层缺陷低碳钢的阴极极化特性

为探索具有剥离涂层缺陷低碳钢的腐蚀规律与机理,以环氧树脂作为涂层材料,于实验室对Q235钢人为模拟制作了面积比例为4.91%的大块剥离涂层缺陷,采用交流阻抗技术研究了剥离涂层缺陷对Q235钢于w(NaCl)=3.5%的NaCl水溶液中的腐蚀特性和阴极保护效果的影响.试验结果表明,在较短的浸泡时间里,在阴极极化电位下涂层缺陷下方金属基体的腐蚀程度低于在自然腐蚀电位下的腐蚀程度;但在较长的浸泡时间里,阴极极化状态与自然腐蚀状态下金属基体具有相似的腐蚀程度及腐蚀特性,说明在电解质溶液大量浸入涂层后将使阴极保护的作用严重降低,而涂层下金属与电解质溶液间的缝隙腐蚀是导致阴极保护效果降低的主要原因.

Cathodic polarization characteristic of low carbon steels with disbonded coating holidays

In order to investigate corrosion behaviour and mechanism of low carbon steels with disbonded coating holidays, the bulk disbonded coating holidays with area proportion 4.91% were simulated on surface of Q235 steel specimen taking epoxy resins and ZrO2 as materials of coating. The influence of bulk disbonded coating holidays with area proportion 4.91% on corrosion characteristic of Q235 steel in 3.5 NaCl% water solution and the effectiveness of cathodic protection were investigated by EIS. Experiments show that the corrosion of steels under disbonded holiday on free corrosion potential is heavier than that on cathodic polarization potential on shorter immersing time. On the other hand, the corrosion has similar degree and characteristic at two potential conditions on longer immersing time, which shows that large amount of electrolyte solution infiltrating into coating leads to the decrease in the effectiveness of cathodic protection because of crevice corrosion between steel and electrolyte solution beneath coating.