【摘要】 分析了电解剥离过程中热镀锌合金化镀层的阳极溶解机制。结果表明,在GA镀层电解剥离的初始阶段,主要发生Zn的氧化,电解剥离过程中存在Zn和Fe之间的电耦合反应。由于镀层中微裂纹的存在,阴极反应区和镀层裂纹缝隙中会同时发生析氢反应,从而导致电偶腐蚀发生并形成诱导电流。当电解质溶液中存在氯离子时,Zn和Fe之间也会发生电耦合反应,该反应可以在一个非常小的局部区域内进行,反应过程中,氢的形核析出既可以是氢离子的重组,也可以是少量Zn和Fe的溶解反应。GA镀层中Fe-Zn金属间化合物同时发生电化学反应而溶解的现象只能在缝隙中发生,由于细小缝隙表面形成的活化区非常小,因此,GA镀层中的Fe-Zn相将分别发生溶解,从而保证了GA镀层中不同相之间的电压跃迁。更多还原

【Abstract】 Mechanism of anodic dissolution of galvannealed coating during coulometric stripping was examined by means of XRD,electrolytic stripping test and FE-SEM observation of surface morphology of the coating. The results show that at the beginning of the electrolysis,Zn oxidation occur mainly,and there occur galvanic coupling reactions between Zn rich and Fe rich phases during the coulometric stripping. Because of the cracks in the galvannealed coating,cathodic reaction zones at the coating surface and in the cracks are formed where hydrogen reduction takes place during anodic dissolution,which leads to an induced current as the result of galvanic corrosion. When the electrolyte solution contents chloride ions,the galvanic coupling reactions of Zn and Fe are possible; these reactions can take place at very localized areas at the coating surface,and in these reactions,the protons formed can either recombine with the hydroxide ions,or promote further dissolution of the Zn and Fe fractions. Simultaneous dissolution of the Fe-Zn intermetallic phases can only take place through the cracks in galvannealed coatings,because the surface active area within these cracks is small,compared to the total dissolution area,so the Fe-Zn intermetallic phases will dissolve separately,and thus ensuring the potential step transit between the different phases.更多还原