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,将环氧煤沥青作为涂层材料,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,并采用交流阻抗技术研究了剥离涂层缺陷对Q235钢于3.5%NaCl水溶液中的腐蚀特性和阴极保护效果的影响.结果表明,在较短的浸泡时间和阴极极化电位下,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,这说明在电解质溶液大量浸入涂层后将严重降低阴极保护的作用,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 Characteristics of Low Carbon Steel with Debonding Coating Holidays

In order to investigate the corrosion behavior and mechanism of low carbon steel with debonding coating holidays, the bulk dis bonded coating holidays with area proportion 4.91% were simulated on the surface of Q235 steel specimen with epoxy coal tar coating. The influence of bulk debonding coating holidays on the corrosion characteristics of Q235 steel in 3.5 % NaC1 solution and cathodic protection effect were investigated by EIS. Experimental results show that with shorter time immersing, the corrosion of steel be- low coating holiday under cathodic polarization potential is less than that under free corrosion potential. But after long time im- mersion, the corrosion degree and characteristics under both situ- ations are similar, which demonstrate that large amounts of elec- trolyte solution infiltrating into coating will lead to the decrease of cathodic protection effect because of crevice corrosion between steel and electrolyte solution beneath coating.