Morphological and chemical characterization of oxide films produced by plasma anodization of 5052 aluminum alloy in solution containing sodium silicate and sodium phosphate

Resumo

Plasma anodization or plasma electrolytic process is a treatment that has been studied for surface modification of various alloys, mainly light alloys such as Al, Mg and Ti. The different combinations among the process parameters allow the deposition of oxide films with diverse or functional properties, which obviously depend on the morphological and chemical characteristics of the film structures. This work shows the results of plasma anodization used in the treatment of 5052 aluminum alloy, using a basic electrolyte solution containing sodium silicate (Na2SiO3) and small proportions of sodium phosphate (Na3PO4). X-ray diffraction (XRD) and infrared (IR) spectroscopy were used for chemical structural analysis of the films, and the surface morphology of the samples was investigated by a scanning electron microscope (SEM). The films resulting from the processes are basically alumina (Al2O3) combined with silicate, with a slightly rough and porous surface, and thickness in the order of micrometers. Corrosion tests carried out in NaCl solution (3.5 wt%) show that all films have a higher chemical resistance compared to the bare 5052 Al alloy.