A study of vitamin B influence on the morphology, roughness, and reflectance of electropolished aluminum in H3PO4–H2SO4 mixture

Abstract

The galvanostatic polarization method used to determine the electrodissolution process of aluminum metal (Al) in acids (phosphoric acid; H3PO4, and sulfuric acid; H2SO4) mixture solution. The investigate of anode potential–limiting current (IL) measured in solution that include of the vitamins B (VB). This research showed an improvement produced in electropolishing (EP) of Al, in the exist of VB, which occurs through adsorption of molecules on the metal surface. The comparison study established by using a different additive: vitamin B1 (VB1), vitamin B2 (VB2), vitamin B6 (VB6), and vitamin B12 (VB12) to evaluate the best one. Adding of VB to Al dissolution bath leads to reduce IL, where the minimum obtained's value for VB12 above other type's value, which according to its chemical structure. By indicating the increases in the surface viscosity of the additives formed over Al, which influences the planarization capacity of the electrolyte. VB adsorbed on the Al surface found to conserve the energy established, resulting in the increased charge transfer resistance and the increase of the overpotential for oxygen and hydrogen.The impact effect of the temperature (T) and acid ratios (v/v %) in a solution are evaluated to determine the preferable conditions in the dissolution process. The calculated IL value will increase by increasing solution’s T in moderated acid ratio. A limiting plateau observed at 35 °C in 60% H3PO4: 40% H2SO4 mixture solution, considered an ideal condition for EP of Al. Activation parameter's values confirm that the dissolution is an endothermic procedure and a character of diffusion.The influence of increasing concentration (C) (1 × 10−4–10 × 10−4 mol·L−1) of VB completed and comprehend, to deduce the relationship between IL and C. Surface morphology, reflection, and roughness of polished samples examined with a scanning electron microscope (SEM), Vis-IR spectroscopy and profilometry. Appreciated and effective results in morphology SEM images occurred at 35 °C by adding optimum C (5 × 10−4 mol·L−1) of VB to a solution mixture; representing a perfect in surface texture. The highest reflectance and lowest roughness values under optimal condition recorded to confirm the SEM results. Keywords: Galvanostatic polarization, Electropolishing (EP), Scanning electron microscope (SEM), Surface roughness, Vitamin B