Study on application of laser in maskless localized electrodeposition and surface quality enhancement
To obtain electrodeposited layers with different patterns, the additional auxiliary measures such as mask prepared by photoresist are usually required for traditional electrodeposition (ECD) technology, which may reduce the flexibility and convenience of this method. Meanwhile, the ultrashort pulsed laser can be introduced into ECD process and increase current density in the selected area on cathode, and has potential in helping achieve maskless localized ECD. In this paper, the picosecond (ps) laser-assisted ECD (LECD) method is studied, in which a cyclic laser scanning scheme is used to produce different electrodeposited layers on the cathode substrate. In addition, the realizing mechanism of localized ECD is discussed, and the surface quality of Ni-P coating prepared by LECD is evaluated. The results show that the electrodeposited layers with different sizes (1 × 1 mm, 2 × 2 mm and 3 × 3 mm) can be obtained by laser selective irradiation on the copper substrate (10 × 10 mm), demonstrating that the critical current can be increased to reach the reaction conditions in the irradiated zone by the laser-caused thermal effects. Analysis also shows that the theoretical diameter of zigzag edge can be calculated, which is consistent with that of actual electrodeposited layer, indicating that the precision and localization of electrodeposited layer is controllable by adjusting laser processing parameters. Furthermore, measurement shows that a surface roughness of 0.012 μm and better surface flatness can be obtained by LECD under a pulse energy of 16 μJ, and the amorphous degree Ni-P can be increased by the thermal and photoelectric effects of ps laser irradiation. Besides, the corrosion potential and current density are -0.19 V and 3.83 × 10-6 A/cm2, respectively, and the AC impedance spectrum also indicates a higher electron transfer resistance, illustrating better corrosion resistance can be achieved by LECD (16 μJ).