带有线缺陷熔结环氧/X70钢涂装体系在3.5%NaCl中的电化学行为

Electrochemical behavior of a fusion bonded epoxy coating with linear defects/carbon steel X70 system in 3.5% NaCl solution

使用电化学阻抗(EIS)方法研究了带有线缺陷的熔结环氧/X70钢涂装体系在3.5%Na-Cl中的电化学行为.通过在试样表面以合适的角度划一个20mm×20mm的十字叉,划透至基体,来制得缺陷.结果表明,它的腐蚀失效过程大致可以分为三个步骤在浸泡初期,试样的电化学行为类似裸钢;在中期,随着裸露金属腐蚀产物的增多,会在线缺陷内部造成塞积,使得缺陷内部pH值降低,涂层粘结接头中的离子键发生断裂;在后期,随着剥离区域的增大,会在剥离区域形成缝隙腐蚀,进而加速涂层的剥离和基底金属的腐蚀.

The electrochemical behavior of a fusion bonded epoxy （FBE） coating with linear defects/ carbon steel X70 system in 3.5% NaCl solution was studied by electrochemical impedance spectroscopy （EIS） technique. The defects were made on samples at right angle by scribing the sample through the paint down to the bare metal to form a 20 mm ×20 mm cross. Experimental results show that corrosion process can be divided into three stages. In the initial stage of eroding, the electrochemical behavior is similar to that of bare steel. In the interim stage, corrosive outgrowth accumulates in the interior of linear defects. It makes pH of solution in the interior of linear defects fall down and causes the coating bonded joint rupture. In the final stage, EIS data show that along the seams, the FBE coating peels off steel substrate. EIS data had been interpreted and discussed in terms of the time dependence of electrical （paint coating） and electrochemical （steel substrate） parameters. The parameters were associated with interracial processes describing deterioration of the carbon steel/fusion bonded epoxy coating with linear defects system.