Ultrasonic Enhancement of Tin Dissolution in NaOH/H2O2 System: Electrochemical and Passivation Modulation

In the alkaline process for sodium stannate preparation, the oxidative dissolution of tin in the NaOH-H2O2 system originates from a spontaneous electrochemical reaction. This study elucidates the mechanism of ultrasound-enhanced tin dissolution in NaOH/H2O2 solutions from an electrochemical perspective, with particular emphasis on the tripartite regulatory effects of ultrasound on mass transfer, passivation suppression, and reaction pathway modulation. Electrochemical analysis indicates that ultrasound enhances mass transfer by disrupting the diffusion boundary layer, delays passivation, accelerates the exfoliation of the passive layer, and generates hydroxyl radicals that lower cathodic activation barriers. Under the action of 30 W ultrasound, the apparent diffusion coefficient of the solution increases and the passivation process of the tin sheet is delayed (the oxidation peak potential shift changes from −0.76 V to −0.70 V). After the passive layer is exfoliated by ultrasound, the charge transfer resistance decreases by 85.8% (from 8.09 ± 0.01 Ω to 1.15 ± 0.01 Ω). Ultrasound effectively overcomes the kinetic limitations imposed by the passivation layer through a triple synergistic mechanism involving mass transfer enhancement, passivation inhibition, and -OH path regulation.