パルス電解法による硫酸塩浴からのZn-Cr合金電析

概要

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The electrodeposition of Zn-Cr alloys from sulfate solutions was conducted using rectangular pulsed current. Changes in the current efficiency and the Cr content in the deposits with varying values for the average current density showed similar results as seen in direct current plating. Cr in the deposits existed in both its metallic and trivalent states in the pulsed current plating, while no metallic Cr was observed in the deposits in direct current plating. Results thus indicated that the use of pulsed current increased the limiting current of Zn to attain the deposition potential of Cr. The superimposition of direct current on pulsed current allowed a significant increase in the content of metallic Cr in the deposits, suggesting that the superimposition of direct current prevented the reoxidation of Cr in the deposits during the off-time period of pulse plating. Varying the plating conditions resulted in the cathode being polarized to an extremely negative region where mass transport became predominant. At that point, the deposits contained a considerable amount of trivalent Cr, which was the product of hydrolysis resulting from the accelerated decomposition of water.
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