Study Of Electrodeposits On Electrolytic Copper Foil And Electrodeposition Patterns

This dissertation electroplated Zn-Sn and Zn-Sn-Ni alloys by employing alkalescent sulfate-pyrophosphate system on electrolytic copper foil, by optimizing bath composition and composition of compound additives, and employing alkalescent low-chrome bath for passivation and silane coupling agents for closing treatment. Without having been rinsed in water, a quantity of alkalescent hydroxy sustained on the surface of Zn alloy disposed in alkali solution, the hydroxy reacted in the way of dehydration with hydrolyze alky silicon -OH and -SiOH, and the formed film of reticulation closely covering the surface of Zn due to Si-O-Si crosslink in the film. The index of the disposed electrolytic copper foil obviously increased in the properties, including corrosion resistance, heat resistance, agglutinate intensity and peel loss.As indicated by XRD analysis on the electrodeposited Zn-Sn alloy, the deposit was a eutectic compound of Zn andβphase Sn. As shown by polariztion curve and cyclic voltammograms curve test, the process of Zn-Sn discharge was changed more by means of the process of changing Sn²⁺ discharge. As indicated by cyclic voltammograms and cathode polarization curves by different scanning potentials, the elctrodeposition process of Zn-Sn alloy in pyrophosphate salt began with the deposition of Sn at -0.9V, followed by the codeposition of Zn and Sn at -1.25 V. Along with the negative scanning of electrode potential,the Zn content of the deposit increased. As shown by cyclic voltammograms curves at different scanning rates, the codeposition of Zn and Sn was a quasireversible process controlled by diffusion,As indicated by XRD analysis on the electrodeposited Zn-Sn-Ni alloy, the alloy deposit obtained in bath of heliotropin and 2-butyne-1, 4-diol as additives, was composed of Zn, Sn andγphase Ni₅Zn₂₁, among whichγphase Ni₅Zn₂₁ had the most intensified peak. When compound additives were added, the most intensified diffraction peak was the diffraction peak ofγphase Ni₅Zn₂₁,δphase Ni3Zn22 was also observed, and the diffraction peak of Zn was not obtained. This showed that Zn in the deposit existed in metal compound. As indicated by XRD analysis on the electrodeposited Zn-Sn-Ni alloy, the deposit was composed of three pure metals.By comparing the tests and analyses of the Zn-Sn and Zn-Sn-Ni electrodeposits, basic rules of Zn-Sn and Zn-Sn-Ni electrodeposition on electrolytic copper foil have been found, and electrodeposition pattern of Zn-Sn-Ni alloy has been established. The basic rules are that in alkalescent sulfate-pyrophosphate system, the electrocrytalization of Zn-Sn alloy was similar to the process of three-dimensional instant nucleation, and the nucleation process of Zn-Sn-Ni ternary alloy was similar to the process of three-dimensional successive nucleation controlled by diffusion. The elctrodeposition occured in the interface of electrode/solution, and the nucleation during the initial electrodepostion had an inductive phase; the adsorbed atoms congregated into clusters and formed critical crystal nucleus; the deposits were crystallized and their characteristics developed during the nucleation. The electrodeposition pattern is that the Zn-Sn-Ni electrodeposition on electrolytic copper foil is a three phases cathode process: Sn²⁺ reaction with soluble oxygen, Sn²⁺ reduction with Sn²⁺ adsorbed on the surface of electrode, and the codeposition of the alloy.