Estudo da eletrodeposição de antimônio e estanho-antimônio em meio de cloreto de colina e etilenoglicol

Abstract

The objective of this study was to investigate the effect of the addition of water and temperature on the electrodeposition of antimony (Sb) on platinum (Pt), as well as the influence of the composition of the electrolyte solution on the joint electrodeposition of tin and antimony (SnxSb(1-x)) on copper (Cu) substrate. The corrosion resistance of the SnxSb(1-x) electrodeposits was investigated in 0.1 mol L-1 NaCl medium. All electrodeposits were obtained using electrolyte solutions based on the mixture of choline chloride (ChCl) and ethylene glycol (EG). The morphology, crystal structure and chemical composition of the electrodeposits were analyzed by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Electron Scattering Spectroscopy (EDS), respectively. Additionally, computational studies were conducted to understand the interactions between Sb3+ ions and the other components of electrolyte solutions, using the computational methods of Molecular Dynamics (MD) and Quantum Theory of Atoms in Molecules (QTAIM). The voltammetric results of the Sb3+ ions indicated that the increase in the water content of the electrolyte catalyzed the reduction of the species. The electrodeposits obtained in the absence and presence of water have different morphologies. The DFT simulations indicated that the Sb-Cl interaction is stronger, which suggests the formation of Sb-Cl complexes. The addition of H2O favors the electron affinity of the systems, and the QTAIM results suggest that this additive decreased the electron density of the Sb3+ ions. For the SnxSb(1-x) electrodeposits, SEM images revealed that the coatings exhibited grains and agglomerates. The XRD results indicated the formation of SbSn phases, such as Cu2Sb, Cu6Sn5 and Cu6(Sn,Sb)5. The potentiodynamic (PP) polarization curves showed that all SnxSb(1-x) alloys had an active dissolution region, followed by a passive region. Immersion tests were performed for 24 h, and XRD results revealed Cu, Sn, SnO, SbSn, and Sb2O4 phases. For the samples immersed for 48 h, the Cu, CuSn, SnO2 and SnSb phases were identified. Polarization resistance (Rp) values of 4.60, 14.69, 1.81 kΩ cm2 were achieved for Sn, Sn77Sb23 and Sn37Sb63, respectively. For the coatings Sn77Sb23, Sn and Sn37Sb63, the values obtained from the respective charge transfer strengths (Rtc), obtained by electrochemical impedance spectroscopy, were: 10.5, 1.15 and 1.46 kΩ cm2. Therefore, these results show that the Sn77Sb23 layer is the most resistant to corrosion.