采用丝束电极技术研究液滴下Cu腐蚀行为

Study of Corrosion Behavior of Copper Beneath a Droplet by Means of Wire Beam Electrode Technology

采用丝束电极方法结合电化学阻抗技术研究了Cu在0.6 mol/LNaCl液滴下的腐蚀行为。结果表明:液滴下Cu电极表面表现出明显的不均匀电流分布特征,开始时呈现中心阴极边缘阳极的分布,随腐蚀时间的延长电流分布会发生极性反转,呈现中心阳极边缘阴极的分布。对电极表面形貌及产物的分析结果表明,开始时液滴边缘区即有红棕色产物大量积累,而中心区氧化膜生成则较慢。随着腐蚀时间的延长,电极表面逐渐被红棕色氧化膜完全覆盖,中心区氧化膜开始破坏并生成绿色产物,其破坏程度强于边缘区。据此对液滴下Cu的腐蚀机理进行探究。

The corrosion behavior of copper beneath a droplet of 0.6 mol/L NaCl solution was studied by means of wire beam electrode technique combined with electrochemical impedance spectroscopy （EIS）. The results show that the distribution of galvanic current remains negative at the center and positive at the periphery of copper surface covered by the droplet at the initial stage. And the polarity reversed with the extension of time, i.e. the positive one at the center and the negative one at the periphery. To study more comprehensively, the EIS measurement was conducted at an interval of 2 h for two copper wires selected separately at the center and the periphery, and the change of the local impedances was found consistent with that of the current distributions. Meanwhile, the surface morphology of the electrode and the composition of the corrosion products were also examined by using scanning electron microscope （SEM） and energy dispersive spectrometer （EDS）. At the beginning, reddish brown oxide products formed much quickly and earlier at the periphery rather than at the center. Then, with the extension of time, the electrode surface was totally covered by corrosion products from the periphery to the center. But, the corrosion products film at the center was severely damaged and replaced by malachite green products, while that remained less destructed relatively at the edge. Further, the corrosion mechanism of copper beneath the droplet was explored that it was the formation and transformation of the corrosion products dominated the chang- es of the distribution of the corrosion current.